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S1046: Improved management of plant-parasitic nematodes through modern diagnostic tools and increased use of host resistance

Annual/Termination Reports (SAES-422): [02/01/2010] [02/22/2011] [02/23/2012] [01/10/2013]

Date of Annual Report: 02/01/2010

Report Information:
  • Annual Meeting Dates: 01/08/10 to 01/08/10
  • Period the Report Covers: 10/2009 to 01/2010

    • Participants:
    Brief Summary of Minutes of Annual Meeting:
    The regular meeting of the S-1046 was called to order at 8:40 am on Jan. 8, 2010 in New Orleans, LA by James Starr. Present: Jim Star, Richard Davis, Ed McGawley, Paula Agudelo, Bob Robbins, Sally Stetina, Jon Eisenback, Patricia Timper, and Ron Lacewell (Administrative Advisor).

    A. Approval of Agenda - The agenda was unanimously approved as distributed.

    B. Approval of Minutes - The minutes of the previous meeting were unanimously approved as distributed.

    C. Open Issues - starr welcomed the group to New Orleans. He mentioned that several people who planned to be at the meeting could not be here due to the frigid temperatures back home (Kathy Lawrence, Gary Lawrence, and Charles Overstreet).

    Lacewell expressed concern about the lack of participation and encouraged the group to apply for grant proposals.

    Starr queried the group about meeting times: should we continue the rotation among the member states (TX, FL, GA, LA, MS, TN, AL, AR) or attach the meeting to another conference like we did this year? Although most of the people in attendance were satisfied with S-1046 being held in conjunction with the Beltwide Cotton Conferences, it was agreed that all members should be polled via e-mail. If we continue with the normal rotation, the next meeting will be in either Arkansas or Louisiana.

    McGawley proposed that we perform some cooperative project as we had done in years past (but not done recently). One of the problems was that many of these projects were never published. We should indentify a common project that we can also publish.

    Starr said that in the Business meeting, he was planning on appointing project coordinators who might facilitate initiation and completion of one or more common projects. One idea was that we conduct a survey to identify the root-knot species associated with major crops in each participating state.

    D. State Reports (final year of S-1015) Arkansas. Bob Robbins presented a project involving rotating soybean cultivars containing different resistance genes. Soybean cyst populations have been kept at low levels for 7 years. He has also been screening soybean lines from all over for resistance to the reniform nematode.

    ARS Georgia. Richard Davis developed a new cotton line (GA120R1B3) with a high level of resistance to Meloidogyne incognita and improved yield and fiber quality. This was achieved through backcrossing and single seed descent. A germplasm release should be completed very soon. Patty Timper discussed two projects with Pasteuria. In one project, endospore densities increased to higher levels in a rotation with eggplant, corn, and peanut than in other crop rotations. The other project involved the effect of soil texture and nematicide treatment on a Pasteuria infecting reniform nematode.

    ARS Mississippi. Sally Stetina presented several project dealing with reniform nematode in cotton. She is looking for new sources of resistance from hirsutum and other Gossypium species and evaluating molecular variability in the reniform nematode (microsatellite and SSR). She has found no link between variation and virulence or pathogenicity.

    Louisiana. Ed McGawley is testing Agri-Terra and sister products on strawberry as an alternative to methyl bromide. The product controls both M. hapla and ring nematode. He has also been testing a chemical called Oraphyte and Pasteuria in turf.

    Virginia. Jon Eisenback presented the findings of surveys of nematodes in soybean (mostly SCN) and corn (stunt, stubby root, lesion, and root-knot nematodes). He has also found a new root-knot in turf  M. lamicainae. This nematode has subsequently been found in other mid-Atlantic states. Damage threshold  40/100 cm3.

    South Carolina. Paula Agudelo has an interest in intraspecific diversity of nematodes (mainly root-knot and reniform nematodes) and how this diversity influences management. She presented research on the effect of temperature on embryogenesis of the reniform nematode. She also has a study looking at the effect of crop rotation on the population structure (utilizing 7 microsatellite markers) of the reniform nematode. Corn has the greatest impact on the population structure, perhaps by selecting for survival of different genotypes.

    Texas. Jim Starr is attempting to identify difference sources of resistance to M. incognita in cotton. He has conducted a half diallel analysis with 5 resistant cotton accessions from Mexico and identified at least 2 unique resistance alleles. He is also trying to develop cotton germplasm with resistance to both root-knot and reniform nematodes. In the near future, he plans to release a high O/L peanut cultivar with good resistance to root-knot nematodes, Tomato Spotted Wilt, and Sclerotinia blight.

    E. Business meeting Bob Robbins (Arkansas) was unanimously approved to be the next Chair of S-1046. Ed McGawley was unanimously approved to be the next Secretary. As a general rule, the secretary will be selected from the rotation 1 year out from the Chair. Starr asked for volunteers to coordinate each of the three objectives. These coordinators would organize the common projects and develop uniform protocols. Stetina volunteered to coordinate Obj. 2 and Agudelo and Eisenback volunteered to coordinate the reniform and root-knot projects, respectively, for Obj. 3. No one was selected for Obj. 1 (Management) because the group did not think this objective was amenable to a common project.

    Stetina suggested that we use SharePoint for sharing files and information over the internet. This program would be particularly useful once we establish common projects.

    Adjournment:Meeting was adjourned at 3:45 pm by Jim Star. Minutes submitted by: Patricia Timper

    Accomplishments:
    As this is a new project there are no research accomplishments to report at this time. Participants have completed their initial organization into interest groups and individuals have been selected to coordinate regional collaborative efforts under objectives 2 and 3.

    Impact Statements:
    1. No impact statements available due to the project having received approval for initiation in only December 2009.
    Last Modified: 09-Mar-2010

    Date of Annual Report: 02/22/2011

    Report Information:
  • Annual Meeting Dates: 01/07/11 to 01/08/11
  • Period the Report Covers: 10/2009 to 09/2010

    • Participants:
    Brief Summary of Minutes of Annual Meeting:
    (Improved management of plant-parasitic nematodes through modern diagnostic tools and increased use of host resistance)

    The meeting was convened at 1:00 PM in the Marriott Marquis Hotel in Atlanta, GA on January 7, 2011. Scientists in attendance (and their state designation) were: Agudelo (SC), Davis (GA), Dickson (FL), Eisenbach (VA), Koenning (NCSU), Lawrence (MS), Lawrence (AL), McGawley (LA), Nguyen (MO), Robbins (AR), Starr (TX), Stetina (MS), Timper (GA), Lacewell (Administrative Advisor, TX). Chen (MN) was absent. The reading of the minutes from the previous were dispensed with and approved as distributed via email to members. Members gave oral state reports. With the impending arrival of bad weather in the Atlanta area, the meeting continued until 6:40 PM in order to include the business meeting. At the business meeting Stetina lead a discussion of cooperative activities for 2011 with reniform nematode. Members will collect specimens of reniform nematode from infested fields in their states. Single mature females will be dissected from root systems and quick frozen at -80 C in 1 M NaCl. Since these samples will contain dead nematodes there will be no need need for an APHIS permit from the USDA. Stetina and colleagues in Stoneville, MS where will extract and amplify DNA from these samples for molecular analysis. Eisenbach and Agudelo also indicated their intentions to cooperate on improving methods for identification of root knot nematode species. In other discussion, McGawley was elected a chairman for the 2011 meeting. Lacewell then made comments from his standpoint as the administrative advisor to the group. First, he congratulated the members related to getting enthusiasm back into the team. The research members are actively working together to solve issues for agriculture including the horticulture industry. The group met briefy for breakfast on January 8 and then departed to avoid the adverse weather.

    Accomplishments:
    Objective 1: Integrate resistant cultivars with other nematode management tactics to reduce selection pressure on nematode populations and communities. (AR) I tested 161 soybean varieties new to the Arkansas Soybean Variety Testing program and 64 breeding lines and varieties from Southern Public Soybean Breeders for resistance to the reniform nematode (Rotylenchulus reniformis) in soybean (6 from Arkansas; 20 from Clemson; 20 from Missouri; 2 from USDA, Jackson, TN; 16 from Virginia Tech). All 296 soybean varieties in the 2010 Arkansas Soybean Variety Testing were also tested for Root-knot (Meloidogyne incognita) and Soybean Cyst Nematode races 2, 3, 5, and 14 (the most prevalent races in Arkansas). The results of this testing can be accessed at the following: http://www.arkansasvarietytesting.com/crop/data/5 administered by Terry Kirkpatrick. In a study I initiated in 2003 on the study of the effects of rotation of soybeans with 3 different soybean resistance sources (mode of resistance) to the soybean cyst nematode in St. Francis (Pine Tree Station) county, I have completed the eight year of the rotation in cooperation with Terry Kirkpatrick. When all rotations are compared the yield is best and the nematode numbers are least when Anand is the variety planted. A similar study rotating 3 Roundup Ready varieties with different resistance reactions has completed its fifth year at Pine Tree also. It became obvious during 2009 and became more pronounced in 2010 that some bio-control agent has become prevalent in this test as most of the plots at harvest had no detectable nematodes.

    (FL) The root-knot nematode tomato cultivar, Crista was tested for marketable yield and galling on roots in two spring and two autumn trials. Evaluations included fumigated and nonfumigated treatments and all trials included a root-knot nematode susceptible cultivar. In three of these trials fruit yield with nonfumigated Crista ranged from 33% to 113% greater than that of the nonfumigated susceptible cultivars, whereas in one trial fruit yield of Crista was 17% less than that of the susceptible cultivar. In three of the four trials when plots of Crista were treated with various fumigants (chloropicrin, potassium metam, 1,3-D, 1,3-D+chloropicrin) yield was increased from 7 to 42% over nonfumigated plots of Crista. In one trial, however, yield of Crista was decreased 21% when fumigated compared with nonfumigated Crista. Galling indices on nonfumigated Crista ranged from 0 to 2%, whereas galling on nonfumigated susceptible cultivars ranged from 29 to 53%. The low percentage galling of Crista vs. susceptible cultivars suggest that the root-knot nematode resistant Mi-1 gene in Crista was maintained and not broken by soil temperature. (AL) The reniform nematode, Rotylenchulus reniformis, is a leading economic pest in cotton in Alabama. Six soil types common to Alabama were evaluated for their effects on the reproduction of R. reniformis under irrigated and non-irrigated conditions. The test was conducted in microplots placed in a factorial within a RCBD replicated five times. The soil types evaluated were a Dothan sandy loam (S-S-C = 57-28-15), a Decatur silt loam (S-S-C = 23-49-28), a Hartsells fine sandy loam (S-S-C = 51-38-11), a Ruston very fine sandy loam (S-S-C = 59-33-8), a Lloyd loam (S-S-C = 52-23-25), and a Vaiden clay (S-S-C = 5-42-53). Significant interactions between soil type and irrigation occurred for nematode reproduction and yield. At harvest, R. reniformis populations were significantly higher (P <0.10) in the Decatur silt loam over the Hartsells fine sandy loam, the Ruston very fine sandy loam, and the Pacolet sandy loam. The Decatur silt loam also had higher populations than the Vaiden clay and the Dothan sandy loam by an average of 3,785 and 5,647 vermiform/150cc soil respectively. Soil types with greater than 50% silt + clay (Decatur silt loam and Vaiden clay) had an average of 83% more R. reniformis than those without. Rotylenchulus reniformis populations were higher in the irrigated plots by an average of 54% at mid-season and an average of 30% at harvest. The Vaiden clay yielded significantly higher (P <0.10) than all other soil types, while the Ruston very fine sandy loam yielded significantly lower (P <0.10) than all other soil types. Yields were significantly higher (P <0.10) in the non-irrigated plots. The combination of soil type and irrigation is directly related to R. reniformis reproduction and can potentially be used with other factors to predict cotton yield loss. (GA) Pasteuria species are bacterial parasites of nematodes. In a field study in Georgia, fewer Pasteuria spores were observed in the sandiest areas of the field and in locations treated with Telone than in the other locations. Similar numbers of spores were observed in the Temik treatment and the control. It is likely that there was greater leaching of spores below the sampling zone in the sandier areas. Telone reduced populations of the reniform nematode, thereby reducing the number of available hosts for reproduction of Pasteuria sp. There was a negative correlation between numbers of reniform nematodes and Pasteuria sp.: as the proportion of nematodes with attached spores increased, the numbers of reniform per volume of soil decreased, indicating that the bacterium may be suppressing the nematode population. (MS) A four year rotation system was developed and planted in 2009 using corn, cotton, soybean and peanut as alternate and non-hosts. All crops were grown to maturity and yields collected. Yields for continuous crops were lower in year two.

    (NC-Koenning) Soybean lines and cultivars with potential resistance derived from PI437564 were evaluated for yield and resistance to cyst nematode field trials located in three counties. Resistance to Races 1, 3, 9 and 14 were ineffective against SCN at these locations and lines with race 2 resistance had much greater yields. A soybean cultivar with resistance to races 1,2,3,5,9 and 14 was developed with resistance derived from Anand (Hartwig x Holiday) and will be released in 2011.

    (MN) Two field sites were established in Waseca and Lamberton, Minnesota, in 2003 and 2008, respectively, to determine the effect of different sequences of SCN-resistance sources (PI 887888, Peking, and PI437654) on dynamics of SCN population densities and their virulence phenotypes (races or HG Types). Waseca site was infested with initial population of SCN race 3, and the main aim of the experiment at this site was to determine how the cultivar sequences influence the changes of the SCN population from avirulent to virulent type on cultivars carrying certain resistance genes. At Lamberton site, the initial SCN population was race 1 that can overcome PI88788 resistance, and the main aim of the experiment at this site was to determine whether any cultivar sequence can change the population from virulent type to avirulent type or change to other HG Types so that the PI88788-source cultivars can be used. SCN population densities differed following different sequence of soybean cultivars, and susceptible soybean resulted in higher egg population density than resistant cultivars. Among the three SCN-resistant cultivars, the cultivar carrying PI88788 resistance supported highest SCN egg population density, the cultivar carrying Peking resistance intermediate, and cultivar carrying PI437654 resistance supported lowest SCN egg population density. Based on the data of HG Type analysis of the populations collected in 2007, 2008, and 2009, SCN populations selected by cultivar with PI 88788 source of resistance could overcome the resistance of PI 88788, and Peking-selected SCN population can overcome the resistance in Peking, not each other. In contrast, PI 437654 selected SCN population that could overcome both Peking and PI 88788 sources of resistance, although the population still had low reproduction potential on PI 437654.

    (SC) We finished a rotation study in which we followed the changes in genetic structure of a field population of reniform nematode. The rotations included: 1) cotton, corn, cotton, corn; 2) susceptible soybean, corn, susceptible soybean, corn; 3) resistant soybean, cotton, resistant soybean, cotton; 4) corn, cotton, corn, cotton; 5) continuous susceptible soybean; and 6) continuous cotton. Each crop was grown for a cycle of 120 days (total of 4 cycles for each rotation scheme) and DNA was extracted from 1,000 individuals for AFLP analysis after each cycle. The host plant exerted clear selection pressure and altered the predominant genotype. The most distinct effects were observed when resistant or susceptible soybean was used in a rotation scheme. Continuous cotton appeared to maintain the diversity of the genotype, but allowed for genetic drift from the original field genotype. Continuous soybean maintained the original field genotype for a longer period of time. These results suggest that the use of susceptible soybean as a host may be more useful for maintaining field genotype when culturing reniform nematodes in a greenhouse.

    (TX) Integrate resistant cultivars into management system. Have determined that temperature sensitive Mi gene resistance in tomato can be used successfully in west Africa if the nematode population is M arenaria, M. incognita, or M. javanica. RK- resistant peppers have limited use due to poor yield potential.

    (VA) A field survey of root-knot nematodes in tobacco has been initiated to evaluate the long-term effect of the RK1 gene on nematode species and race structure. We anticipate that the prolonged use of this gene to manage root-knot has caused a shift in the species and races from Meloidogyne incognita race 1 to M. incognita races 2 and 4 and to M. arenaria and M. javanica.

    Objective 2: Identify and incorporate new sources of resistance into elite germplams lines and cultivars.

    (AR) I am collaborating with Drs. Grover Shannon (Soybean Breeder) and Tri D. Vuong (Soybean Biotechnologist) on developing reniform molecular markers for reniform nematode resistance in soybean. We tested 190 lines in 2010 (5 reps each). I am conducting proprietary contract studies with Phytogen Seed Company looking for reniform resistance in cotton.

    (AL) Rotylenchulus reniformis (reniform nematode) can be a yield-limiting factor for upland cotton (Gossypium hirsutum L.). Resistance was discovered in a wild cotton relative, transferred to an upland background and released as the germplasm LONREN. We tested F2:4 lines from the cross LONREN-1 × Fibermax 966 in two fields, one infested with reniform nematode and one not infested. Twenty resistant lines and 20 susceptible lines were tested, with the objective of determining the effect of the LONREN resistance gene on yield, agronomic traits, and fiber quality in a nematode-infested and nematode-free environment. Lines with the LONREN resistance gene were stunted during early season growth and yielded less than their susceptible counterparts in the nematode-infested field. Nematode populations were reduced in plots where lines carrying the LONREN resistance gene were planted. There were no yield differences in the nematode-free field. Fiber quality was largely unaffected by the LONREN resistance gene, except that lines carrying the gene tended to have greater fiber strength.

    (GA) GA 120R1B3 is a non-commercial breeding line of cotton (Gossypium hirsutum L.) jointly released by the USDA Agricultural Research Service and the Agricultural Experiment Station at the University of Georgia in 2010. Greenhouse and field evaluations confirmed that GA 120R1B3 has a high level of resistance to Meloidogyne incognita (the southern root-knot nematode) and has high yield and excellent fiber quality characteristics. Field evaluations for yield and fiber quality were conducted both in fields infested with M. incognita and in fields without M. incognita. In the presence of the nematode, the resistance in GA 120R1B3 significantly reduces yield loss. The source of resistance in GA 120R1B3 was M-120 RNR. GA 120R1B3 has a level of resistance to M. incognita that is equivalent to that in M-120 RNR, but GA120R1B3 has significantly better lint percentage and fiber quality than M-120 RNR. GA 120R1B3 has yield and fiber quality generally comparable to commercial cultivars, and a lint percentage that was often greater than the commercial standards. GA 120R1B3 had good yield and excellent fiber quality in both the presence and absence of M. incognita.

    (MN) Several soybean lines carrying SCN-resistance different from the sources PI 88788 and Peking were used for breeding SCN-resistance cultivars. Crosses were made in 2009 and 2010 and the progenies of the crosses will be evaluated for SCN resistance.

    (MS) Twenty soybean varieties were evaluated for resistance to the root-knot nematode. Fourteen varieties were resistant and six moderately susceptible to the root-knot nematode. One hundred and twenty varieties were screened for resistance to the reniform nematode. Ten varieties were resistant, thirty-two varieties were moderately susceptible, seventeen varieties were susceptible and sixty-one varieties were highly susceptible.

    (NC-Davis) The roots of transgenic soybean plants engineered to express RNAi against three parasitism genes of soybean cyst nematode were analyzed for production of small RNAs to compare the actual transgene expression with observed levels of SCN resistance. Extremely low expression of RNAi constructs complementary to SCN parasitism genes that encode a mimic of plant CLE-like protein, an effector protein that interacts with plant spermidine synthase, and a novel SCN parasitism protein was observed in all transgenic soybean lines. Modifications of the RNAi vector used in soybean are currently in progress to improve transgene expression and resistance to SCN in soybean.

    (MS-Stetina) Efforts to incorporate useful levels of resistance to reniform nematode (Rotylenchulus reniformis) into upland cotton (Gossypium hirsutum) continued. Moderate levels of resistance from less-adapted day-neutral Texas race stock lines have been identified, and select lines will be tested in replicated trials in 2011 pending receipt of sufficient seed from the winter nursery in Tecoman, Mexico. In this project, we also are working to transfer high levels of reniform nematode resistance from five unique relatives of upland cotton (G. aridum, G. arboreum, G. longicalyx, G. barbadense, and G. herbaceum), and marker assisted selection is being used as appropriate to facilitate this effort. Molecular marker analysis indicated that we have BC4F2 plants with resistance from G. aridum, G. arboreum, or both sources combined. Continued testing and selection for desirable agronomic traits is anticipated for 2011 and 2012, with possible germplasm release(s) from this population in 2013. Collaborative work with cotton breeders at Mississippi State University resulted in F3 and F4 progeny with confirmed resistance from G. longicalyx (Lonren 1 and Lonren 2 sources of resistance) that show acceptable to excellent yield potential and fiber quality, including some that combine reniform nematode resistance with the nectariless trait. The Lonren 1 and Lonren 2 sources used as the resistance donors are being evaluated for suspected sensitivity to the herbicide fluometuron, though results to date indicate that neither is more sensitive than the commercial G. hirsutum cultivar used as a control. Evaluation of F2 progeny from a cross between plants with resistance from G. longicalyx (Lonren 2) and G. aridum (selected BC2F1 plants selected from a G. arboreum//G. hirsutum/G. aridum population) demonstrated that the resistance genes are not allelic and in some cases work together to result in greater suppression of the reniform nematode population. Resistance from G. barbadense accession GB 713 transferred to a G. hirsutum background by Dr. Forest Robinson (retired USDA, ARS, College Station, TX) has been crossed to materials adapted for Mississippi and the midsouthern U.S., including several nectariless lines, with progeny currently at the F3 generation. Accessions of G. herbaceum are being screened to identify novel sources of resistance for future germplasm development.

    Identification of reniform nematode resistance in advanced breeding lines and accessions from the soybean (Glycine max) germplasm collection was initiated. A total of 60 entries were screened to date based on female development on roots, and eight of these were selected for further testing to evaluate effects of nematode reproduction and confirm the resistant reaction. USDA ARS breeding line Glycine max DS-880 was released and has a moderate level of reniform nematode resistance. One parent of an existing population of 273 recombinant inbred lines was demonstrated to have a moderate level of resistance to reniform nematode in initial screenings, so an extensive phenotypic evaluation of the population was initiated to identify markers associated with resistance.

    (TX) New Sources of resistance. Have released two cotton breeding lines (Tam RKRNR 9 and Tam RKRNR 12) that have a high level of resistance to M. incognita and moderate resistance to R. reniformis, Have confirmed that five primitive G. hirsutum genotypes from Mexico represent unique sources of resistance to M. incognita and have initiated a backcross breeding program to introgress this resistance into modern cotton germplasm.

    Objective 3: Facilitate and improve identification of nematode species and races. (AR) My current student Marco Cordero and I are involved in the morphological and molecular taxonomy of the Criconemoidea, a widespread and often damaging nematode group of over a dozen genera. Included will be photographic records of all species studied and descriptions of several new species we have identified as there are several species we are in the process of describing that are new to science. I have been cooperating with a student at the University of Tabriz in Iran (Majid Pedram) on the identification and publication of new species in the virus vectoring genera Longidorus and Xiphinema and the description of new species in several other dorylime genera. (LA) The comparative reproduction and pathogenicity of isolates of Rotylenchulus reniformis from Alabama, Arkansas, Hawaii, Louisiana, Mississippi and Texas on cotton was evaluated in microplot trials. Prior to initiation of microplot trials, ten clonal populations of each geographic isolate were derived from single egg masses. Reproduction of the clonal populations of each geographic isolate were evaluated in greenhouse studies with Stoneville LA887 cotton by assessing the numbers of vermiform stages in soil and eggs per gram of root tissue 60 days after inoculation. On the basis of these trials, each repeated once, one clonal population of each of the six isolates was selected for use in microplot trials. Averaged over the two trials, clonal population designations selected for use in microplot trials and their respective reproduction values (R, where R=Pf/Pi) and numbers of eggs per gram of root were: AL-8 (R=14.9, eggs=202); AR-3 (R=30.4, eggs=525); HI-9 (R=20.2, eggs=183); LA-3 (R=18.2, eggs=517.); MS-7 (R=25.7, eggs=602) and TX-10 (R=42.8, eggs=938). Data from full-season (147 days) microplot trials, averaged over 2 years, showed significant differences (Tukeys HSD test (P< 0.05%)) among isolates of reniform nematode in both reproduction and pathogenicity. Dry plant weight at harvest averaged 370.6 g for the non-inoculated control. All isolates except the one from HI produced root weights at harvest that were reduced significantly below that of the control. Harvest weights for plants inoculated with LA-3 and MS-7 were significantly lower than those from the other four geographic regions. The comparative reproduction and pathogenicity of isolates of Rotylenchulus reniformis from Alabama, Arkansas, Hawaii, Louisiana, Mississippi and Texas on soybean was evaluated in microplot trials. Prior to initiation of microplot trials, ten clonal populations of each geographic isolate were derived from single egg masses. Reproduction of the clonal populations of each geographic isolate were evaluated in greenhouse studies with Deltapine 4331 soybean by assessing the numbers of vermiform stages in soil and eggs per gram of root tissue 60 days after inoculation. On the basis of these trials, each repeated once, one clonal population of each of the six isolates was selected for use in microplot trials. Averaged over the two trials, clonal population designations selected for use in microplot trials and their respective reproduction values (R, where R=Pf/Pi) and numbers of eggs per gram of root were: AL-7 (R=3.5, eggs=1,082); AR-4 (R=26.7, eggs=2,186); HI-1 (R=30.2, eggs=1,624); LA-3 (R=30.2, eggs=1,656); MS-2 (R=43.9, eggs=5,215) and TX-5 (R=55.4, eggs=4,329). Data from full-season (126 day) microplot trials, averaged over 2 years, showed significant differences (Tukeys HSD test (P< 0.05%)) among isolates of reniform nematode in both reproduction and pathogenicity. Dry plant weight at harvest averaged 273.3 g for the non-inoculated control. All isolates except the ones from HI and TX produced root weights at harvest that were reduced significantly below that of the control. With the exception of the MS-2 isolate, harvest weights for plants inoculated with AR-4 were significantly lower than those from the other four geographic regions. Relative to the control, numbers and dry weights of pods per plant at harvest were reduced significantly by all reniform iolates except those from AL and HI.

    (MS) A species specific primer pair (RrITS1) showed specificity to R. reniformis. RrITS1 generated amplicons on the 4 different populations of R. reniformis tested. The species-specific primer pair showed specificity in both the glasshouse and field populations. A positive diagnoses for a single vermiform reniform nematode could be detected from soil when using generating Ct values below 37. Two developmental phases of the syncytium were determined during soybean cyst parasitism. Syncytia undergoing resistant and susceptible reactions appear the same during early development. The resistance response is complete by 9 dpi. Using microdissection of the syncytia and neighboring cells identifed genes that characterize the resistance phase. The most highly induced pathways include jasmonic acid biosynthesis, 13-lipoxygenase pathway, S-adenosyl methionine pathway, phenylpropanoid biosynthesis, suberin biosynthesis, adenosylmethionine biosynthesis, ethylene biosynthesis from methionine, flavonoid biosynthesis and the methionine salvage pathway. These pathways, along with coumarin biosynthesis, cellulose biosynthesis and homogalacturonan degradation are induced. Custom pathway analyses implicate the jasmonic acid defense pathway as a factor involved in the resistant reaction of G. max.

    (SC) We developed 10 microsatellite loci appropriate to study the genetic diversity of reniform nematode. We included individuals from 15 geogrpahic locations and report data that supports a high inbreeding coefficient for this species. Interestingly, this high frequency of inbreeding resulting in a high frequency of homozygosity, occurs even with high level of genetic variation. The combination of high homozygosity and relatively high genetic variation suggest that studies examining the rates and patterns of shared versus fixed alleles between populations will be possible. Thus, these loci will be useful for studying reniform nematode population genetics

    (TX) Have adopted the PCR-based protocol of Adam et al. (2006) for the identification of M. marylandi.

    (VA) A new technique that uses an annular ring in the stage condenser produces images with increased resolution and enhanced surface morphology that are look like images produced with a scanning electron microscope. Annular rings increase resolution by making the illumination coherent (light waves that vibrate with constant phase relationships). The initial picture appears similar to a photographic negative, but is inverted into a positive with image processing software and a computer. This new technique of illumination increases the value of the observation of perineal patterns for identification of Meloidogyne species by increasing resolution and enhancing surface morphology.

    Impact Statements:
    1. Developed 10 microsatellite loci appropriate to study the genetic diversity of reniform nematode.
    2. Custom pathway analyses implicate the jasmonic acid defense pathway as a factor involved in the resistant reaction of Glycine max to Heterodera glycines.
    3. First in U.S.A. to demonstrate reproductive and pathological differences in geographic populations of Rotylenchulus reniformis on soybean and cotton.
    4. Modifications of the RNAi vector used in soybean are currently in progress to improve transgene expression and resistance to SCN in soybean.
    5. A soybean cultivar with resistance to races 1,2,3,5,9 and 14 was developed with resistance derived from Anand (Hartwig x Holiday) and will be released in 2011.
    6. A field survey of root-knot nematodes in tobacco has been initiated to evaluate the long-term effect of the RK1 gene on nematode species and race structure. We anticipate that the prolonged use of this gene to manage root-knot has caused a shift in the species and races from Meloidogyne incognita race 1 to M. incognita races 2 and 4 and to M. arenaria and M. javanica.
    7. Released two cotton breeding lines (Tam RKRNR 9 and Tam RKRNR 12) that have a high level of resistance to M. incognita and moderate resistance to R. reniformis
    Last Modified: 26-Feb-2011

    Date of Annual Report: 02/23/2012

    Report Information:
  • Annual Meeting Dates: 01/07/12 to 01/07/12
  • Period the Report Covers: 10/2010 to 10/2011

    • Participants:
    Brief Summary of Minutes of Annual Meeting:
    The S-1046 meeting was convened at 9:00 AM in the Orlando World Center Marriott in Orlando, FL on January 7, 2011. Scientists in attendance (and their state designation) were: P. Agudelo (SC), S. Chen (MN) R. Davis (GA), D. Dickson (FL), K. Lawrence (AL), G. Lawrence (MS), E. McGawley (LA), C. Overstreet (LA), R. Robbins (AR) and J. Starr (TX). R. Lacewell (Administrative Advisor, TX). S. Stetina (MS) absent but report provided. Students present and their study directors: Claudia Holguin (SC  P. Agudelo) Addison Plaisance (LA  E. McGawley) Deborah Xavier (_LA  C. Overstreet)

    Each member was asked to introduce themselves for all members and tell their affiliations with their respective universities or USDA-ARS employment. Afterward budget and departmental updates were discussed amongst the members present. The minutes from the 2010 meeting were accepted and approved. Starr (TX) provided the motion to accept the minutes and received a second by K. Lawrence (AL). Ron Lacewell (Administrative Advisor, TX) provided the committee information on our project status and made comments from his standpoint as the administrative advisor to the group. Dr. Lacewell congratulated the members related to getting enthusiasm back into the team. The research members are actively working together to solve issues for agriculture including the horticulture industry. It was emphasized to include new members and check with previous members that have not attended to determine if they were going to continue with the project. Several scientists were mentioned to contact for future attendance. Funding and budget concerns were discussed. Members present then provided oral state reports. At the business meeting it was stressed to provide bullet points and accomplishments to the secretary (G. Lawrence, MS) as soon as possible in order to get the final report complete and approved. It was proposed by K. Lawrence (AL) that we meet with members of the W-2186 Multi-State group in 2011. After a brief discussion, Starr (TX) provide the motion to accept this meeting and was seconded by McGawley (LA). The motion passed and K. Lawrence (AL) chair of W-2186 and G. Lawrence (MS) chair of S-1046 will work out the details to have a combined meeting in 2012. Meeting locations were discussed and possible meeting dates. It was proposed to meet in November similar to meeting dates that were held previously. Dickson (FL) will check for the meeting date of the Methyl Bromide conference so there would be no conflicts. In other discussions G. Lawrence (MS) will serve as chair the 2012 annual meeting and P. Agudelo (SC) will serve as secretary. The group then planned to meet at 6:00 for a group dinner The 2011 annual meeting of the S-1046 Multistate Research Project was adjourned at 4:05 pm.

    Accomplishments:
    Objective 1: Integrate resistant cultivars with other nematode management tactics to reduce selection pressure on nematode populations and communities. Soybean: (AR) One hundred forty seven soybean varieties new to the Arkansas Soybean Variety Testing program and 134 breeding lines and varieties from Southern Public Soybean Breeders for examined for resistance to the reniform nematode (Rotylenchulus reniformis) in soybean (68 from Arkansas; 21 from Clemson; 16 from Missouri; 4 from USDA, Jackson, TN; 1 from Virginia Tech and 24 from Southern Illinois - Carbondale). Progeny 5191, Delta Grow DG5252R3Y, JTN-5203 were similar to the resistant checks Forrest, Anand and Hartwig. These may be useful in a cotton-soybean rotation to reduce numbers of reniform nematode and allow cotton to be grown economically. In 2003 on the effects of rotation of soybeans with 3 different soybean resistance sources (mode of resistance) to the soybean cyst nematode at the Pine Tree Experiment Station, St. Francis county. The ninth year of the rotation is completed. When rotations are compared the nematode numbers are least when Anand is the variety planted. A study rotating 3 Roundup Ready varieties with different resistance reactions has completed its sixth year at Pine Tree. A bio-control agent has become prevalent in this test and has been converted to a biocontrol of soybean cyst nematode study. (LA) Comparative reproduction and pathogenicity of isolates of Rotylenchulus reniformis from Alabama, Arkansas, Hawaii, Louisiana, Mississippi and Texas on soybean was evaluated in microplot trials. Prior to initiation of microplot trials, ten populations of each geographic isolate were derived. Reproduction of the single egg-mass (SEM) populations of each geographic isolate were evaluated in greenhouse studies with Deltapine 4331 soybean by assessing the numbers of vermiform stages in soil and eggs per gram of root tissue 60 days after inoculation. On the basis of these trials, each repeated once, one SEM population of each of the six isolates was selected for use in microplot trials. Averaged over the two trials, SEM populations selected for use in microplot trials and their respective reproduction values (R, where R = Pf/Pi) and numbers of eggs per gram of root were: AL-7 (R = 3.5, eggs = 1,082); AR-4 (R = 26.7, eggs = 2,186); HI-1 (R = 30.2, eggs = 1,624); LA-3 (R = 30.2, eggs = 1,656); MS-2 (R = 43.9, eggs = 5,215) and TX-5 (R = 55.4, eggs = 4,329). Data from full-season (126 day) microplot trials, averaged over 2 years, showed significant differences (Tukeys HSD test (P d 0.05%)) among isolates of reniform nematode in both reproduction and pathogenicity. (MN) A long-term field plot studies in Minnesota demonstrated that that SCN populations selected by cultivar with PI 88788 source of resistance can only overcome the resistance of PI 88788 not the Peking and PI 437654; Peking-selected SCN populations can overcome the resistance in Peking, not PI 88788 and PI 437654; and PI 437654 can select SCN populations to overcome both sources of resistance PI 88788 and Peking.

    (MS) Statina Identification of reniform nematode resistance in advanced breeding lines and accessions from the soybean (Glycine max) germplasm collection continued. Lines not previously reported as being resistant that were identified as moderately resistant or resistant in our initial screenings were advanced to longer trials in which reniform nematode reproduction is measured. The final run of this experiment to confirm the phenotype and provide additional insight into the level of resistance in each line is in progress. A full report on this work is tentatively scheduled for presentation at the Southern Soybean Disease Workers annual meeting in March 2012. One parent of an existing population of 273 recombinant inbred lines was demonstrated to have a moderate level of resistance to reniform nematode in initial screenings, so an extensive phenotypic evaluation of the population is underway to identify markers associated with resistance.

    Cotton: (AL) A trial to reduce the risk of damage to cotton by Rotylenchulus reniformis was conducted in a 26 ha field in south Alabama in 2009 - 2011. The field was delineated into three management zones using soil electrical conductivity (EC) and elevation, the nematicides 1, 3-dichloropropene, aldicarb, oxamyl and abamectin were applied alone and in various combinations within each zone with an untreated control. Population densities of R. reniformis prior to nematicide treatment were 535, 1096 and 71 vermiform life stages/150cm3 of soil for zones 1, 2 and 3, respectively. Zones 1, 2 and 3 averaged increasing volumetric water content (P < 0.1) of 0.138, 0.150 and 0.184/cm3, throughout the season. Evaluation of the interaction of R. reniformis population and soil moisture on cotton yields indicate that the driest zone, Zone 1, was at the highest risk of yield loss and benefitted with yield gains (P< 0.1) from higher rates of nematicides. Although Zone 1 supported only half the initial R. reniformis population compared with Zone 2, the combination of soil moisture and nematode stress in Zone 1 resulted in a larger yield increase over the untreated control. Zone 2 with the highest initial nematode populations and adequate soils moisture did not benefit from the nematicide with a yield increase as neither did Zone 3 with low nematode numbers and good soil moisture. The factor of water availability throughout the growing season should be considered in risk assessment when creating site-specific management zones for Rotylenchulus reniformis.

    Cotton cultivars occupying the largest acreage of Alabama were examined for susceptibility to Fusarium wilt (FW); subsequently fungal isolates were collected to confirm Fusarium oxysporum f. sp. vasinfectum (FOV) presence. Symptoms of FW were initially observed in mid-June and increased in severity through July and August. FW incidence culminated with 16% of the Rowden and < 1% of the resistant control M-315 plants dying, respectively. FOV was isolated on APDA from hypocotyls regions of all cotton cultivars except PHY367WRF, ST5458B2RF, and M-315. The numbers of root-knot nematodes increase in all the cotton varieties. The standard susceptible cotton, Rowden, averaged 2149 root-knot eggs per gram of root while the M-315 resistant cotton supported only 88 eggs per gram of root. All cotton cultivars supported higher populations of root-knot (P > 0.001) as compared to M-315 except PHY 367 WRF. This PHY 367 WRF was also the only cultivar less susceptible to the nematode as compared to the Rowden susceptible control. Seed cotton yield varied from a low of 1151 lb/A in the susceptible Rowden to a high of 4467 lb/A in the PHY 367 WRF plots. The PHY 367 WRF, PHY 565 WRF, ST 4288 B2RF, and ST 5458 B2RF cultivars all produced more cotton (P > 0.05) as compared to Rowden. All of the cotton cultivars produced yields similar to the resistant cotton M-315 except Deltapine DP 0949 B2RF. Genetic analysis of each FOV isolate, by cotton variety, was characterized by partial sequences of the translational elongation factor (EF-1±) gene, indicating very diverse clades of genotypes within this Alabama field. Combined analysis conducted in AL and in CA (Rebecca Bennett) identified genotype races 1, 4, 8, and several undefined genotypes to be present. Results of this field test indicate resistance to FW does exist in our commercial cotton cultivars, and FOV in Alabama appears to be extremely diverse genetically. Further greenhouse tests to confirm isolate pathogenicity found none of the races produced root necrosis without the nematode present.

    (GA) Timper  Davis Nematodes are among the leading cause of yield loss in cotton in the US. In greenhouse studies in Georgia, infection of cotton by the cotton root-knot nematode (Meloidogyne incognita) or the reniform nematode (Rotylenchulus reniformis) induced a plant defense response known as systemic acquired resistance (SAR). Increased levels of P-peroxidase, G-peroxidase, and catalase are associated with the induction of SAR, and the levels of these enzymes were significantly increased compared to untreated plants. Application of a chemical analog of salicylic acid known to induce SAR in some plants caused the greatest increases. SAR induced by R. reniformis reduced the root galling caused by subsequent infection with M. incognita by 33 to 36% and reproduction of M. incognita by 35 to 45%. SAR induced by M. incognita infection reduced reproduction of R. reniformis by 18 to 26%.

    Winter cover crops increase organic matter in soil. Some fungal pathogens of nematodes may be able to utilize this organic matter as an alternative food source. We hypothesized that NemOut (Paecilomyces lilacinus) would provide greater control of Meloidogyne incognita in cotton when a winter cover crop has been grown compared to winter fallow. In a greenhouse experiment, we showed that growing a rye cover crop and leaving the residue on the soil surface resulted in greater percentage suppression of the nematode by P. lilacinus in the succeeding cotton crop than leaving the soil fallow (62% with rye vs 36% with fallow).

    (MS) Stetina Efforts to incorporate useful levels of resistance to reniform nematode (Rotylenchulus reniformis) into upland cotton (Gossypium hirsutum) continued. Moderate levels of resistance from less-adapted day-neutral Texas race stock lines were tested in replicated trials in 2011; three lines were selected for advanced testing in 2012. In this project, we also are working to transfer high levels of reniform nematode resistance from five unique relatives of upland cotton (G. aridum, G. arboreum, G. longicalyx, G. barbadense, and G. herbaceum), and marker assisted selection is being used as appropriate to facilitate this effort. Molecular marker analysis indicated that we have BC4F3 plants with resistance from G. aridum, G. arboreum, or both sources combined. Continued testing and selection for desirable agronomic traits is anticipated for 2012, with possible germplasm release(s) from this population in 2013. Collaborative work with cotton breeders at Mississippi State University resulted in F4 and F5 progeny with confirmed resistance from G. longicalyx (Lonren 1 and Lonren 2 sources of resistance) that show acceptable to excellent yield potential and fiber quality, including some that combine reniform nematode resistance with the nectariless trait. The Lonren 1 and Lonren 2 sources used as the resistance donors were found to be no more sensitive to the herbicide fluometuron than commercial G. hirsutum cultivars. Seed increases of advanced generation materials with moderate resistance from G. hirsutum or resistance from G. barbadense were completed in 2011 in anticipation of replicated plot tests in 2012. Resistance from G. barbadense accession GB 713 transferred to a G. hirsutum background by Dr. Forest Robinson (retired USDA, ARS, College Station, TX) has been crossed to materials adapted for Mississippi and the midsouthern U.S., including several nectariless lines, with several populations currently at the F4 and F5 generations. Approximately 1,500 accessions of G. arboreum and 90 accessions of G. herbaceum were planted in the field in 2011, and single plants were agronomically characterized and self pollinated to represent each accession in subsequent resistance screening and associated germplasm development research. We considered this a necessary first step in identifying novel sources of resistance for future germplasm development, as many of the accessions showed considerable segregation for agronomic traits such as leaf shape, plant height, and flowering.

    (MS) Lawrence A four year rotation system was developed and planted in 2009 using corn, cotton, soybean and peanut as alternate and non-hosts. All crops were grown to maturity and yields collected. Yields for some of the rotation crops were low in 2009 due to delays in harvest from inclement weather. In 2010 crops yields were good. In the plots that were planted with the same crop in consecutive years, yields were lower. The data analysis of harvest for year four 2011produced similar results.

    (MS) Lawrence Nematode Detection Service - A web service is currently being developed in which the end user can upload ground or sub-orbital hyperspectral reflectances of their fields and see the results of the prediction models in an easy to use interface which is graphically appealing. The inclusion of a web service to this project increases the commerciality of this project

    Vegetables: (FL) Tomato cultivars with the Mi-1 gene are under investigation as an alternative to using fumigant nematicides. Evaluations of Amelia, Crista, and Red Bounty included fumigated and nonfumigated treatments and in both spring and autumn trials compared with a root-knot nematode susceptible tomato cultivar.

    Objective 2: Identify and incorporate new sources of resistance into elite germplams lines and cultivars. Soybean: (AR) In collaborating with Drs. Grover Shannon (Soybean Breeder) and Tri D. Vuong (Soybean Biotechnologist) on developing reniform molecular markers for reniform nematode resistance in soybean, 190 lines in 2010 (5 reps each). Also proprietary contract studies with Phytogen Seed Company looking for reniform resistance in cotton are in progress. (MN) Soybean germplasms with resistance different from the common sources of resistance PI 88788 and Peking were identified, and a few lines were used in breeding SCN-resistant cultivars. Four SCN-resistance QTLs in the soybean line PI 567516C were determined, including two significant QTLs and two suggestive QTLs in PI 567516C. The two significant QTLs were detected on chromosome 10 and chromosome 19, and the SNP markers associated with the two QTLs may be useful in marker-assisted selection.

    (MS) Lawrence Soybean Cyst Nematode Race 15 or now 2? Soybean varieties submitted for inclusion in the Mississippi variety evaluation trials are examined in the greenhouse for possible resistance to the root-knot, reniform and soybean cyst nematodes. Testing for 2011 has started with the soybean cyst nematode host race 15. One hundred soybean varieties have currently been examined and sixty additional varieties have been inoculated are in progress in the greenhouse. All varieties have been susceptible to this Mississippi SCN population.

    Corn: (MS) Lawrence Eighty-two corn hybrids were examined in the greenhouse for root-knot nematode resistance. All hybrids were susceptible with a reproductive factor ranging from Rf 10.4  149.9.

    Cotton: (AL) In 2011, we tested F2:4 lines from the cross LONREN-1 × Fibermax 966 in two adjacent cotton fields of the same soil type, one was infested with reniform nematode and one was not infested. Twenty resistant lines and 20 susceptible lines were tested, with the objective of determining the effect of the LONREN resistance gene on yield, agronomic traits, and fiber quality in a nematode-infested and nematode-free environment. Cotton lines with the LONREN resistance gene were severely stunted and yielded less than their susceptible counterparts in the nematode-infested field. Nematode populations were reduced in plots where lines carrying the LONREN resistance gene were planted. There were no yield differences in the nematode-free field. Fiber quality was largely unaffected by the LONREN resistance gene, except that lines carrying the gene tended to have greater fiber strength.

    (MS) Stetina Members of this regional project agreed to initiate a coordinated testing effort to identify host plant resistance to reniform nematode (Rotylenchulus reniformis) in cotton (Gossypium hirsutum) and soybean (Glycine max). The first step in this process is to select genetically unique populations of reniform nematode for coordinated testing. During 2011, members of this project team and cooperators in Hawaii sent 10 individual adult female reniform nematodes from their respective research collections to Dr. Stetinas lab in Stoneville, MS. Research collections from Mississippi (S. Stetina and G. Lawrence), Alabama (K. Lawrence), Georgia (R. Davis), South Carolina (P. Agudelo), and Hawaii (B. Sipes) are represented. DNA extraction and amplification from most of these samples is complete, with the last set of materials to be processed by the end of January 2012. During spring 2012, molecular markers developed in a previous study will be applied to the samples to assess the genetic diversity among these research collections. By summer of 2012, we should be able to select diverse populations for use in screening cotton and soybean germplasm for reaction to reniform nematode. Coordinated testing of advanced germplasm could begin as soon as fall 2012.

    (TX) Have collaborated with USDA researchers in the development of BARBREN-713, an upland cotton genotype with resistance to root-knot and reniform nematodes. This material will be officially released in 2012. Have advance three breeding lines with unique sources of reistance to root-knot nematodes to the BC2F2 generation

    Objective 3: Facilitate and improve identification of nematode species and races. (AR) With Marco Cordero, we are investigating the morphological and molecular taxonomy of the Criconemoidea, a widespread and often damaging nematode group of over a dozen genera. Included will be photographic records of all species studied and descriptions of several new species we have identified as there are several species we are in the process of describing that are new to science. The first of 5 chapters has been submitted for publication and 2 more chapters are almost ready for submission. During 2011 a species of Cyst nematode, Heterodera urticae previously found only in Europe was found and reported.

    (MS) G. Lawrence/ Klink/K. Lawrence Molecular diagnostic tests have been developed and utilized to diagnose and to confirm Rotylenchulus sp. in Mississippi soils. DNA primers and probes were developed for a TaqMan probe quantitative PCR (qPCR)-based assay. The qPCR procedure could accurately detect the presence of Rotylenchulus sp. with a strong correlation (R² = 0.9924) between the morphologically (visually) observed number of number of soil extracted R. reniformis and the qPCR estimated number of nematodes from metagenomic DNA isolated from the same soil sample.

    (SC) Research includes studying the distribution and population density of Hoplolaimus species in soybean and cotton fields in South Carolina. Our objective is also to identify ecological and management factors potentially correlated to the presence of specific species of lance nematodes, and to develop molecular diagnostic methods to identify the main species of lance nematodes.

    (TX) Have adopted the PCR-based protocol of Adam et al. (2006) for the identification of M. marylandi.

    Impact Statements:
    1. Soybean-cotton rotations will continue to be the most economical means of nematode control until resistance is found in cotton.
    2. Rotations have an environmental advantage over chemical nematicides by having no long lasting effect on the field or crop and is environmentally safe to use.
    3. We identified cotton varieties resistance to Meloidogyne incognita are available to our growers. Resistant varieties also a less susceptible to Fusarium wilt.
    4. Precision nematicide application can enhance cotton yield when the field is infested with Rotylenchulus reniformis.
    5. Moisture stress potential is as important as initial nematode populations when selecting and applying nematicides.
    6. There is a lack of consistence in fruit yield of the resistant cultivars when grown in nonfumigated soil even though galling indicies were consistent very low.
    7. The low percentage galling of resistant tomato cultivars vs. susceptible cultivars indicates that the root-knot nematode resistant Mi-1 gene in tomato was not broken by soil temperature under polyethylene films.
    8. Root- systemic acquired resistance (SAR) against nematodes in cotton could be induced by applying a chemical analog of salicylic acid. SAR may contribute significantly to reducing the damage in cotton caused by nematodes.
    9. Research at LSU during this period was the first in the U.S. to document variation in reproduction and pathogenicity among geographic isolates of the reniform nematode, Rotylenchulus reniformis on soybean.
    10. In 2010, research from the LSU AgCenter was also the first to document similar reproductive and pathogenic variation in reniform populations on cotton.
    11. The host response of the crops used in our studies for resistance or susceptibility to plant-parasitic nematodes demonstrates the importance of continual variety examinations. There is a lack of resistance to the root-knot nematodes in corn hybrids currently available. With soybean there are indications that the introduction or shift of a SCN race will upset the resistance available to this specific race. We recovered a population of SCN identified as SCN race 15. In earlier studies after screening over 300 varieties found none to be resistant to this population. In examining recently developed varieties, resistance appears to be lacking.
    12. Rotations with non-host crops will continue to be a major role in nematode management even with resistant varieties.
    13. Nematode Detection Service - a web based service for nematode detection will allow the end-user to upload from ground data and see their results graphically.
    14. A molecular diagnostic technique for the reniform nematode will increase the accuracy of detecting the presence and quantification of this pest in the soil.
    15. Soil samples are processed from South Carolina planted with soybean, cotton, and turf. We have identified Hoplolaimus galeatus and H. stephanus associated with turf and H. columbus associated with soybean and cotton. We have validated molecular methods for their identification.
    16. In South Carolina, the Columbia Lance Nematode is found in 21% of soybean samples (124/600) and 59% of cotton samples (237/400), with densities ranging from 10 to 330 nematodes per 100 cc of soil.
    17. In North Carolina, lance nematodes are found in only 10% of soybean fields, specifically in samples from Robeson, Scotland, Bertie, Camden, Pasquotank, Tyrell, Washington and Beaufort counties. The densities ranged from 10 to 70 nematodes per 100 cc of soil. Interestingly, none of these were identified as Columbia Lance Nematode. All of the species found were H.galeatus-like.
    18. Additional samples from other southeastern states are included and have found Hoplolaimus magnistylus in Arkansas and Tennessee.
    19. Collaborated with USDA researchers in the development of BARBREN-713, an upland cotton genotype with resistance to root-knot and reniform nematodes will be officially released in 2012.
    20. dvance three breeding lines with unique sources of resistance to root-knot nematodes to the BC2F2 generation
    Last Modified: 23-Feb-2012

    Date of Annual Report: 01/10/2013

    Report Information:
  • Annual Meeting Dates: 10/31/12 to 11/02/12
  • Period the Report Covers: 10/2011 to 09/2012

    • Participants:
    Brief Summary of Minutes of Annual Meeting:
    This was a joint meeting with the Western Regional Research Project (W-2186) group, organized by Kathy Lawrence (AL) and Gary Lawrence (MS).

    November 1, 2012: The meeting was convened at 8:15 a.m. in the Mississippi Coastal Research and Extension Center in Biloxi, MS. Members of the W-2186 group were also in attendance. USDA members were unable to travel to participate in this years meeting. Started with oral reports by members of W-2186. Ron Lacewell commented on this being a good joint meeting, and warned about potential large cuts in funding for agricultural research. He emphasized the importance of interactions between states for this project and suggested adding more members. David Thompson added that it is important not to overlap objectives between multi-state projects. Oral reports for S-1046 were presented as follows: Charles Overstreet (LA- reniform nematode on cotton), Don Dickson (FL- root-knot nematodes on tomato and peanut), Ed McGawley (LA-reniform nematode on cotton), Vince Klink (MS- soybean cyst nematode), Jim Starr (TX- root-knot nematodes on peanut and cotton), Jon Eisenback (VA- root-knot nematodes), Paula Agudelo (SC  lance nematodes), Robert Robbins (AR-soybean cyst and reniform nematodes).

    November 2, 2012: Oral reports by members of W-2186 continued. Final S-1046 report was presented: Senyu Chen (Minnesota; SCN population dynamics). Then, graduate students from Auburn University and Mississippi State University gave progress reports on their research (7 presentations). Business meeting: Called to order at 11:30 a.m. Jim Starr moved to approve minutes from previous meeting. Steve Thomas seconded and all agreed. Minutes were approved as distributed by e-mail. The next meeting will be in Clemson, South Carolina in November of 2013. The dates will be decided soon. Paula Agudelo (incoming President) will communicate with members for planning. Graduate student presentations will be encouraged at this meeting. Jon Eisenback (incoming Secretary) will plan the meeting in 2014 in Williamsburg, Virginia. Potential new members were discussed. Travis Faske from University and Arkansas and Chuck Johnson from Virginia Tech will be invited to join. Jim Starr requested that formal thanks for the sailing excursion organized by Kathy and Gary be included in the minutes. All agreed in that this was an extraordinary experience. Meeting adjourned.

    Accomplishments:
    Objective 1: Integrate resistant cultivars with other nematode management tactics to reduce selection pressure on nematode populations and communities. Soybean: (AR) One hundred forty seven soybean varieties new to the Arkansas Soybean Variety Testing program and 134 breeding lines and varieties from Southern Public Soybean Breeders for examined for resistance to the reniform nematode (Rotylenchulus reniformis) in soybean (68 from Arkansas; 21 from Clemson; 16 from Missouri; 4 from USDA, Jackson, TN; 1 from Virginia Tech and 24 from Southern Illinois - Carbondale). Progeny 5191, Delta Grow DG5252R3Y, JTN-5203 were similar to the resistant checks Forrest, Anand and Hartwig. These may be useful in a cotton-soybean rotation to reduce numbers of reniform nematode and allow cotton to be grown economically. In 2003 on the effects of rotation of soybeans with 3 different soybean resistance sources (mode of resistance) to the soybean cyst nematode at the Pine Tree Experiment Station, St. Francis county. The ninth year of the rotation is completed. When rotations are compared the nematode numbers are least when Anand is the variety planted. A study rotating 3 Roundup Ready varieties with different resistance reactions has completed its sixth year at Pine Tree. A bio-control agent has become prevalent in this test and has been converted to a biocontrol of soybean cyst nematode study.

    (LA) Comparative reproduction and pathogenicity of isolates of Rotylenchulus reniformis from Alabama, Arkansas, Hawaii, Louisiana, Mississippi and Texas on soybean was evaluated in microplot trials. Prior to initiation of microplot trials, ten populations of each geographic isolate were derived. Reproduction of the single egg-mass (SEM) populations of each geographic isolate were evaluated in greenhouse studies with Deltapine 4331 soybean by assessing the numbers of vermiform stages in soil and eggs per gram of root tissue 60 days after inoculation. On the basis of these trials, each repeated once, one SEM population of each of the six isolates was selected for use in microplot trials. Averaged over the two trials, SEM populations selected for use in microplot trials and their respective reproduction values (R, where R = Pf/Pi) and numbers of eggs per gram of root were: AL-7 (R = 3.5, eggs = 1,082); AR-4 (R = 26.7, eggs = 2,186); HI-1 (R = 30.2, eggs = 1,624); LA-3 (R = 30.2, eggs = 1,656); MS-2 (R = 43.9, eggs = 5,215) and TX-5 (R = 55.4, eggs = 4,329). Data from full-season (126 day) microplot trials, averaged over 2 years, showed significant differences (Tukeys HSD test (P d 0.05%)) among isolates of reniform nematode in both reproduction and pathogenicity.

    (MN) A long-term field plot studies in Minnesota demonstrated that that SCN populations selected by cultivar with PI 88788 source of resistance can only overcome the resistance of PI 88788 not the Peking and PI 437654; Peking-selected SCN populations can overcome the resistance in Peking, not PI 88788 and PI 437654; and PI 437654 can select SCN populations to overcome both sources of resistance PI 88788 and Peking.

    (MS) Statina Identification of reniform nematode resistance in advanced breeding lines and accessions from the soybean (Glycine max) germplasm collection continued. Lines not previously reported as being resistant that were identified as moderately resistant or resistant in our initial screenings were advanced to longer trials in which reniform nematode reproduction is measured. The final run of this experiment to confirm the phenotype and provide additional insight into the level of resistance in each line is in progress. A full report on this work is tentatively scheduled for presentation at the Southern Soybean Disease Workers annual meeting in March 2012. One parent of an existing population of 273 recombinant inbred lines was demonstrated to have a moderate level of resistance to reniform nematode in initial screenings, so an extensive phenotypic evaluation of the population is underway to identify markers associated with resistance.

    Cotton: (AL) A trial to reduce the risk of damage to cotton by Rotylenchulus reniformis was conducted in a 26 ha field in south Alabama in 2009 - 2011. The field was delineated into three management zones using soil electrical conductivity (EC) and elevation, the nematicides 1, 3-dichloropropene, aldicarb, oxamyl and abamectin were applied alone and in various combinations within each zone with an untreated control. Population densities of R. reniformis prior to nematicide treatment were 535, 1096 and 71 vermiform life stages/150cm3 of soil for zones 1, 2 and 3, respectively. Zones 1, 2 and 3 averaged increasing volumetric water content (P < 0.1) of 0.138, 0.150 and 0.184/cm3, throughout the season. Evaluation of the interaction of R. reniformis population and soil moisture on cotton yields indicate that the driest zone, Zone 1, was at the highest risk of yield loss and benefitted with yield gains (P< 0.1) from higher rates of nematicides. Although Zone 1 supported only half the initial R. reniformis population compared with Zone 2, the combination of soil moisture and nematode stress in Zone 1 resulted in a larger yield increase over the untreated control. Zone 2 with the highest initial nematode populations and adequate soils moisture did not benefit from the nematicide with a yield increase as neither did Zone 3 with low nematode numbers and good soil moisture. The factor of water availability throughout the growing season should be considered in risk assessment when creating site-specific management zones for Rotylenchulus reniformis.

    Cotton cultivars occupying the largest acreage of Alabama were examined for susceptibility to Fusarium wilt (FW); subsequently fungal isolates were collected to confirm Fusarium oxysporum f. sp. vasinfectum (FOV) presence. Symptoms of FW were initially observed in mid-June and increased in severity through July and August. FW incidence culminated with 16% of the Rowden and < 1% of the resistant control M-315 plants dying, respectively. FOV was isolated on APDA from hypocotyls regions of all cotton cultivars except PHY367WRF, ST5458B2RF, and M-315. The numbers of root-knot nematodes increase in all the cotton varieties. The standard susceptible cotton, Rowden, averaged 2149 root-knot eggs per gram of root while the M-315 resistant cotton supported only 88 eggs per gram of root. All cotton cultivars supported higher populations of root-knot (P > 0.001) as compared to M-315 except PHY 367 WRF. This PHY 367 WRF was also the only cultivar less susceptible to the nematode as compared to the Rowden susceptible control. Seed cotton yield varied from a low of 1151 lb/A in the susceptible Rowden to a high of 4467 lb/A in the PHY 367 WRF plots. The PHY 367 WRF, PHY 565 WRF, ST 4288 B2RF, and ST 5458 B2RF cultivars all produced more cotton (P > 0.05) as compared to Rowden. All of the cotton cultivars produced yields similar to the resistant cotton M-315 except Deltapine DP 0949 B2RF. Genetic analysis of each FOV isolate, by cotton variety, was characterized by partial sequences of the translational elongation factor (EF-1±) gene, indicating very diverse clades of genotypes within this Alabama field. Combined analysis conducted in AL and in CA (Rebecca Bennett) identified genotype races 1, 4, 8, and several undefined genotypes to be present. Results of this field test indicate resistance to FW does exist in our commercial cotton cultivars, and FOV in Alabama appears to be extremely diverse genetically. Further greenhouse tests to confirm isolate pathogenicity found none of the races produced root necrosis without the nematode present.

    (GA) Timper  Davis Nematodes are among the leading cause of yield loss in cotton in the US. In greenhouse studies in Georgia, infection of cotton by the cotton root-knot nematode (Meloidogyne incognita) or the reniform nematode (Rotylenchulus reniformis) induced a plant defense response known as systemic acquired resistance (SAR). Increased levels of P-peroxidase, G-peroxidase, and catalase are associated with the induction of SAR, and the levels of these enzymes were significantly increased compared to untreated plants. Application of a chemical analog of salicylic acid known to induce SAR in some plants caused the greatest increases. SAR induced by R. reniformis reduced the root galling caused by subsequent infection with M. incognita by 33 to 36% and reproduction of M. incognita by 35 to 45%. SAR induced by M. incognita infection reduced reproduction of R. reniformis by 18 to 26%.

    Winter cover crops increase organic matter in soil. Some fungal pathogens of nematodes may be able to utilize this organic matter as an alternative food source. We hypothesized that NemOut (Paecilomyces lilacinus) would provide greater control of Meloidogyne incognita in cotton when a winter cover crop has been grown compared to winter fallow. In a greenhouse experiment, we showed that growing a rye cover crop and leaving the residue on the soil surface resulted in greater percentage suppression of the nematode by P. lilacinus in the succeeding cotton crop than leaving the soil fallow (62% with rye vs 36% with fallow).

    (MS) Stetina Efforts to incorporate useful levels of resistance to reniform nematode (Rotylenchulus reniformis) into upland cotton (Gossypium hirsutum) continued. Moderate levels of resistance from less-adapted day-neutral Texas race stock lines were tested in replicated trials in 2011; three lines were selected for advanced testing in 2012. In this project, we also are working to transfer high levels of reniform nematode resistance from five unique relatives of upland cotton (G. aridum, G. arboreum, G. longicalyx, G. barbadense, and G. herbaceum), and marker assisted selection is being used as appropriate to facilitate this effort. Molecular marker analysis indicated that we have BC4F3 plants with resistance from G. aridum, G. arboreum, or both sources combined. Continued testing and selection for desirable agronomic traits is anticipated for 2012, with possible germplasm release(s) from this population in 2013. Collaborative work with cotton breeders at Mississippi State University resulted in F4 and F5 progeny with confirmed resistance from G. longicalyx (Lonren 1 and Lonren 2 sources of resistance) that show acceptable to excellent yield potential and fiber quality, including some that combine reniform nematode resistance with the nectariless trait. The Lonren 1 and Lonren 2 sources used as the resistance donors were found to be no more sensitive to the herbicide fluometuron than commercial G. hirsutum cultivars. Seed increases of advanced generation materials with moderate resistance from G. hirsutum or resistance from G. barbadense were completed in 2011 in anticipation of replicated plot tests in 2012. Resistance from G. barbadense accession GB 713 transferred to a G. hirsutum background by Dr. Forest Robinson (retired USDA, ARS, College Station, TX) has been crossed to materials adapted for Mississippi and the midsouthern U.S., including several nectariless lines, with several populations currently at the F4 and F5 generations. Approximately 1,500 accessions of G. arboreum and 90 accessions of G. herbaceum were planted in the field in 2011, and single plants were agronomically characterized and self pollinated to represent each accession in subsequent resistance screening and associated germplasm development research. We considered this a necessary first step in identifying novel sources of resistance for future germplasm development, as many of the accessions showed considerable segregation for agronomic traits such as leaf shape, plant height, and flowering.

    (MS) Lawrence A four year rotation system was developed and planted in 2009 using corn, cotton, soybean and peanut as alternate and non-hosts. All crops were grown to maturity and yields collected. Yields for some of the rotation crops were low in 2009 due to delays in harvest from inclement weather. In 2010 crops yields were good. In the plots that were planted with the same crop in consecutive years, yields were lower. The data analysis of harvest for year four 2011produced similar results.

    (MS) Lawrence Nematode Detection Service - A web service is currently being developed in which the end user can upload ground or sub-orbital hyperspectral reflectances of their fields and see the results of the prediction models in an easy to use interface which is graphically appealing. The inclusion of a web service to this project increases the commerciality of this project

    Vegetables: (FL) Tomato cultivars with the Mi-1 gene are under investigation as an alternative to using fumigant nematicides. Evaluations of Amelia, Crista, and Red Bounty included fumigated and nonfumigated treatments and in both spring and autumn trials compared with a root-knot nematode susceptible tomato cultivar.

    Objective 2: Identify and incorporate new sources of resistance into elite germplams lines and cultivars. Soybean: (AR) In collaborating with Drs. Grover Shannon (Soybean Breeder) and Tri D. Vuong (Soybean Biotechnologist) on developing reniform molecular markers for reniform nematode resistance in soybean, 190 lines in 2010 (5 reps each). Also proprietary contract studies with Phytogen Seed Company looking for reniform resistance in cotton are in progress.

    (MN) Soybean germplasms with resistance different from the common sources of resistance PI 88788 and Peking were identified, and a few lines were used in breeding SCN-resistant cultivars. Four SCN-resistance QTLs in the soybean line PI 567516C were determined, including two significant QTLs and two suggestive QTLs in PI 567516C. The two significant QTLs were detected on chromosome 10 and chromosome 19, and the SNP markers associated with the two QTLs may be useful in marker-assisted selection.

    (MS) Lawrence Soybean Cyst Nematode Race 15 or now 2? Soybean varieties submitted for inclusion in the Mississippi variety evaluation trials are examined in the greenhouse for possible resistance to the root-knot, reniform and soybean cyst nematodes. Testing for 2011 has started with the soybean cyst nematode host race 15. One hundred soybean varieties have currently been examined and sixty additional varieties have been inoculated are in progress in the greenhouse. All varieties have been susceptible to this Mississippi SCN population.

    Corn: (MS) Lawrence Eighty-two corn hybrids were examined in the greenhouse for root-knot nematode resistance. All hybrids were susceptible with a reproductive factor ranging from Rf 10.4  149.9.

    Cotton: (AL) In 2011, we tested F2:4 lines from the cross LONREN-1 × Fibermax 966 in two adjacent cotton fields of the same soil type, one was infested with reniform nematode and one was not infested. Twenty resistant lines and 20 susceptible lines were tested, with the objective of determining the effect of the LONREN resistance gene on yield, agronomic traits, and fiber quality in a nematode-infested and nematode-free environment. Cotton lines with the LONREN resistance gene were severely stunted and yielded less than their susceptible counterparts in the nematode-infested field. Nematode populations were reduced in plots where lines carrying the LONREN resistance gene were planted. There were no yield differences in the nematode-free field. Fiber quality was largely unaffected by the LONREN resistance gene, except that lines carrying the gene tended to have greater fiber strength.

    (MS) Stetina Members of this regional project agreed to initiate a coordinated testing effort to identify host plant resistance to reniform nematode (Rotylenchulus reniformis) in cotton (Gossypium hirsutum) and soybean (Glycine max). The first step in this process is to select genetically unique populations of reniform nematode for coordinated testing. During 2011, members of this project team and cooperators in Hawaii sent 10 individual adult female reniform nematodes from their respective research collections to Dr. Stetinas lab in Stoneville, MS. Research collections from Mississippi (S. Stetina and G. Lawrence), Alabama (K. Lawrence), Georgia (R. Davis), South Carolina (P. Agudelo), and Hawaii (B. Sipes) are represented. DNA extraction and amplification from most of these samples is complete, with the last set of materials to be processed by the end of January 2012. During spring 2012, molecular markers developed in a previous study will be applied to the samples to assess the genetic diversity among these research collections. By summer of 2012, we should be able to select diverse populations for use in screening cotton and soybean germplasm for reaction to reniform nematode. Coordinated testing of advanced germplasm could begin as soon as fall 2012.

    (TX) Have collaborated with USDA researchers in the development of BARBREN-713, an upland cotton genotype with resistance to root-knot and reniform nematodes. This material will be officially released in 2012. Have advance three breeding lines with unique sources of reistance to root-knot nematodes to the BC2F2 generation

    Objective 3: Facilitate and improve identification of nematode species and races. (AR) With Marco Cordero, we are investigating the morphological and molecular taxonomy of the Criconemoidea, a widespread and often damaging nematode group of over a dozen genera. Included will be photographic records of all species studied and descriptions of several new species we have identified as there are several species we are in the process of describing that are new to science. The first of 5 chapters has been submitted for publication and 2 more chapters are almost ready for submission. During 2011 a species of Cyst nematode, Heterodera urticae previously found only in Europe was found and reported.

    (MS) G. Lawrence/ Klink/K. Lawrence Molecular diagnostic tests have been developed and utilized to diagnose and to confirm Rotylenchulus sp. in Mississippi soils. DNA primers and probes were developed for a TaqMan probe quantitative PCR (qPCR)-based assay. The qPCR procedure could accurately detect the presence of Rotylenchulus sp. with a strong correlation (R² = 0.9924) between the morphologically (visually) observed number of number of soil extracted R. reniformis and the qPCR estimated number of nematodes from metagenomic DNA isolated from the same soil sample.

    (SC) Research includes studying the distribution and population density of Hoplolaimus species in soybean and cotton fields in South Carolina. Our objective is also to identify ecological and management factors potentially correlated to the presence of specific species of lance nematodes, and to develop molecular diagnostic methods to identify the main species of lance nematodes.

    (TX) Have adopted the PCR-based protocol of Adam et al. (2006) for the identification of M. marylandi.

    Impact Statements: (Arkansas) 1. Soybean-cotton rotations will continue to be the most economical means of nematode control until resistance is found in cotton. 2. Rotations have an environmental advantage over chemical nematicides by having no long lasting effect on the field or crop and is environmentally safe to use.

    (Alabama) 1. We identified cotton varieties resistance to Meloidogyne incognita are available to our growers. Resistant varieties also a less susceptible to Fusarium wilt. 2. Precision nematicide application can enhance cotton yield when the field is infested with Rotylenchulus reniformis. 3. Moisture stress potential is as important as initial nematode populations when selecting and applying nematicides.

    (Florida) 1. There is a lack of consistence in fruit yield of the resistant cultivars when grown in nonfumigated soil even though galling indicies were consistent very low. 2. The low percentage galling of resistant tomato cultivars vs. susceptible cultivars indicates that the root-knot nematode resistant Mi-1 gene in tomato was not broken by soil temperature under polyethylene films.

    (Georgia) 1. Root- systemic acquired resistance (SAR) against nematodes in cotton could be induced by applying a chemical analog of salicylic acid. SAR may contribute significantly to reducing the damage in cotton caused by nematodes. (Louisiana) 1. Research at LSU during this period was the first in the U.S. to document variation in reproduction and pathogenicity among geographic isolates of the reniform nematode, Rotylenchulus reniformis on soybean. 2. In 2010, research from the LSU AgCenter was also the first to document similar reproductive and pathogenic variation in reniform populations on cotton.

    (Mississippi) Lawrence 1. The host response of the crops used in our studies for resistance or susceptibility to plant-parasitic nematodes demonstrates the importance of continual variety examinations. There is a lack of resistance to the root-knot nematodes in corn hybrids currently available. With soybean there are indications that the introduction or shift of a SCN race will upset the resistance available to this specific race. We recovered a population of SCN identified as SCN race 15. In earlier studies after screening over 300 varieties found none to be resistant to this population. In examining recently developed varieties, resistance appears to be lacking. 2. Rotations with non-host crops will continue to be a major role in nematode management even with resistant varieties. 3. Nematode Detection Service - a web based service for nematode detection will allow the end-user to upload from ground data and see their results graphically. 4. A molecular diagnostic technique for the reniform nematode will increase the accuracy of detecting the presence and quantification of this pest in the soil.

    (South Carolina) 1. Soil samples are processed from South Carolina planted with soybean, cotton, and turf. We have identified Hoplolaimus galeatus and H. stephanus associated with turf and H. columbus associated with soybean and cotton. We have validated molecular methods for their identification. 2. In South Carolina, the Columbia Lance Nematode is found in 21% of soybean samples (124/600) and 59% of cotton samples (237/400), with densities ranging from 10 to 330 nematodes per 100 cc of soil. 3. In North Carolina, lance nematodes are found in only 10% of soybean fields, specifically in samples from Robeson, Scotland, Bertie, Camden, Pasquotank, Tyrell, Washington and Beaufort counties. The densities ranged from 10 to 70 nematodes per 100 cc of soil. Interestingly, none of these were identified as Columbia Lance Nematode. All of the species found were H.galeatus-like. 4. Additional samples from other southeastern states are included and have found Hoplolaimus magnistylus in Arkansas and Tennessee.

    (Texas) 1. Collaborated with USDA researchers in the development of BARBREN-713, an upland cotton genotype with resistance to root-knot and reniform nematodes will be officially released in 2012. 2. Advance three breeding lines with unique sources of resistance to root-knot nematodes to the BC2F2 generation

    Impact Statements:
    1. - Cotton germplasm BARBREN-713 was identified as the best genotype to work with to develop reniform nematode resistant cotton lines.
    2. - A good rotation, such as corn-cotton, sorghum-cotton or reniform resistant soybean-cotton can restore profitability to fields infested with soybean cyst nematode.
    3. - Nematode Detection Service - a web based service for nematode detection allows the end-user to upload from ground data and see their results graphically.
    4. - A molecular diagnostic technique for the reniform and soybean cyst nematodes increases the accuracy of detecting the presence and quantification of these pests in the soil.
    5. - The release of N7003CN facilitates the use of varieties resistant to root-knot and reniform nematodes. It is the first maturity group VII variety with resistance to race 2 of soybean cyst nematode.
    6. - Sorghum hybrids with good field tolerance to root-knot and lance nematoides have been identified
    7. - Release of peanut cv Webb, a cultivar with resistance to root-knot nematode, sclerotinia blight, tomato spotted wilt virus and has the high oleic to linoleic fatty acid trait.
    8. - Release of BARBREN, a cotton breeding line with resistance to reniform nematode derived from Gossypium barbadense GB713 and resistance to root-knot nematode derived from G. hirsutum M315.
    9. - The use of Meloidogyne incognita resistant tobacco over the last 30-40 years has resulted in a dramatic shift of root-knot species to M. arenaria, M. hapla, and M. javanica and various mixtures of two or more of these four species making the resistance to M. incognita less useful for reducing the economic impact of these root-knot nematodes.
    10. - A new technique for viewing the perineal pattern of root-knot nematodes greatly improves their value for routine species identifications.
    11. - Quantification of the effect of soil texture and irrigation on yield losses caused by reniform nematode on cotton.
    Last Modified: 10-Jan-2013
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