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ABSTRACT: With 4 tablesAbstractReniform nematode (Rotylenchulus reniformis) has become a major pest of cotton in the mid-south area of the United States. Resistance genes, Ren1 and Ren2 from Gossypium longicalyx and Gossypium aridum, respectively, have been identified and introduced into Upland cotton (Gossypium hirsutum). We developed an F2 population of 184 progeny plants by crossing Ren2 -containing plants with a LONREN-2 plant that had the resistance gene Ren1. The F2 plants were evaluated for their resistance to reniform nematodes in a growth chamber. Microsatellite markers BNL2662 and BNL3279 were analysed to assist the selection of proper parental plants and F1 progeny and to study the segregation of the resistance genes in the F2 population. Our results suggested that Ren1 and Ren2 were duplicate genes with Ren1 residing on chromosome 11 (A subgenome) and Ren2 on chromosome 21 (D subgenome). F2 plants containing either Ren1 or Ren2 had significantly fewer nematodes than the susceptible Upland cotton genotype. No significant difference in nematode resistance was found between plants containing Ren1 and those having Ren2, indicating that these two genes may have similar resistance mechanisms. Plants containing both Ren1 and Ren2 appeared to have higher resistance than those with just one of the genes, and pyramiding these two genes may be a valuable tool to cotton breeders when managing this pest.
Plant Breeding 08/2011; 130(6):673 - 678. · 1.60 Impact Factor
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ABSTRACT: Rotylenchulus reniformis is the predominant parasitic nematode of cotton in the Mid South area of the United States. Although variable levels of infection and morphological differences have been reported for this nematode, genetic variability has been more elusive. We developed microsatellite-enriched libraries for R. reniformis, produced 1152 clones, assembled 694 contigs, detected 783 simple sequence repeats (SSR) and designed 192 SSR-markers. The markers were tested on six R. reniformis cultures from four states, Texas, Louisiana, Mississippi and Georgia, in the USA. Based on performance we selected 156 SSR markers for R. reniformis from which 88 were polymorphic across the six reniform nematode populations, showing as the most frequent motif the dinucleotide AG. The polymorphic information content of the markers ranged from 0.00 to 0.82, and the percentage of multiallelic loci of the isolates was between 40.9 and 45.1%. An interesting finding in this study was the genetic variability detected among the three Mississippi isolates, for which 22 SSR markers were polymorphic. We also tested the level of infection of these isolates on six cotton genotypes, where significant differences were found between the Texas and Georgia isolates. Coincidentally, 62 polymorphic markers were able to distinguish these two populations. Further studies will be necessary to establish possible connections, if any, between markers and level of pathogenicity of the nematode. The SSR markers developed here will be useful in the assessment of the genetic diversity of this nematode, could assist in management practices for control of reniform nematode, be used in breeding programs for crop resistance, and help in detecting the origin and spread of this nematode in the United States.
Journal of nematology 06/2009; 41(2):146-56. · 0.52 Impact Factor
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ABSTRACT: Rotylenchulus reniformis is a major problem confronting cotton production in the central part of the cotton belt of the United States of America. In this study, the hypothesis that natural antagonists in some cases are responsible for unusually low densities of the nematode in certain fields was tested by assaying soils from 22 selected fields for the presence of transferable agents in pots containing cotton plants. In one field, soil from four different depth ranges was tested. In the first of two types of assays, 1 part nematode infested soil was added to 9 parts test soil that was left untreated or autoclaved before mixing; this mixture was used to fill pots. In the second type of assay, 1 part test soil was added to 9 or 19 parts pasteurized fine sand, and nematodes were introduced in aqueous suspension. In three experiments representing both types of assay, transferable or autoclavable agent(s) from four fields in South Texas suppressed nematode populations by 48, 78, 90 and 95%. In one experiment, transferable agents in five fields in Louisiana suppressed populations from 37 to 66%. Identification and evaluation of these agents for biological control of R. reniformis merits further study.
Journal of nematology 04/2008; 40(1):35-8. · 0.52 Impact Factor
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ABSTRACT: More plants can be screened for reniform nematode resistance each year if the time involved can be shortened. In this study, the hypothesis that female counts are as efficient as egg counts in identifying resistant genotypes was tested. In two greenhouse experiments Gossypium genotypes which varied from resistant to susceptible to reniform nematode (Rotylenchulus reniformis) were compared to a susceptible control cultivar. Infested field soil served as the inoculum source for the first experiment, and vermiform stages extracted from greenhouse cultures were used to infest soil in the second experiment. Six replicates of each genotype were harvested 25 d after planting and swollen females were counted. The remaining plants were harvested 35 d after planting and eggs extracted from the roots were counted. Processing and counting times recorded in the first experiment were similar for both assessment methods, but 10 additional days were required for egg-based assessment. Contrast analyses showed that assessments based on females per gram of root were equivalent to assessments based on eggs per gram of root for the five genotypes tested in the first experiment and for an expanded set of 13 genotypes tested in the second experiment. The results indicated that either life stage can be used to screen for resistance.
Journal of nematology 10/2006; 38(3):326-32. · 0.52 Impact Factor
