Evaluation of endemic populations of Rotylenchulus reniformis within Louisiana on soybean genotypes with known levels of resistance to soybean cyst nematode

Abstract

Variation among geographic isolates of Rotylenchulus reniformis (reniform nematode) has been demonstrated both inter- and intrastate in the USA. A greenhouse study was conducted to evaluate sources of resistance present in soybean genotypes used in the soybean cyst nematode ‘‘HG Type’’ test (Pickett, PI 88788, PI 90763, PI 437654, PI 209332, PI 89772, Cloud, Lee 74) using five geographic isolates (from Ouachita, Rapides, East Carroll, Tensas, and Catahoula parishes of Louisiana) of R. reniformis. Experiments, conducted under greenhouse conditions, were established as an 8 3 5 3 4 design representing the eight ‘‘HG Type’’ genotypes 3 five reniform nematode isolates 3 four replications. After 31 days, egg masses were stained and numbers present on a 2-g subsample were enumerated at 40x using a dissecting microscope. Vermiform life stages of R. reniformis in soil were extracted from a 250 g subsample of soil. Data was analyzed using analysis of variance (ANOVA) for a factorial design using ‘‘Fit Y by X’’ module of SAS JMP Pro, version 12.0 (SAS Institute; Cary, NC). PI 90763 and PI 89772 showed significant variation in numbers of vermiform life stages in soil across all five reniform nematode isolates. Reproduction of the nematode was greatest on Lee 74 and least on PI 90763 and PI 89772. Results add further support to the hypothesis of virulence phenotypes within Louisiana and among major southern cotton and soybean producing states. Current research is focused on the development of a greenhouse based differential host assay for R. reniformis and evaluation of a laboratory based assay in employing a soilless growth-pouch environment.