Genetic Variability of Rotylenchulus reniformis

Rotylenchulus reniformis, reniform nematode, is a polyphagous pest commonly found parasitizing cotton in the southeastern United States. We developed and optimized 10 polymorphic microsatellite loci found in reniform nematode and tested them on 160 individual reniform nematodes to determine informative genetic variation of isolates from the southeastern United States, Colombia, Japan, and from the species Rotylenchulus parvus. No significant gametic disequilibrium was detected between any pair of loci, and most loci were not in expected Hardy-Weinberg proportions. A positive F_IS coefficient was observed at all 10 loci, suggesting a high level of inbreeding at these loci. Most isolate locations exhibited significant genotypic differentiation and moderate to very high genetic differentiation based on F_ST analysis. The most consistently differentiated isolates were found reproducing parthenogenetically in Japan. These isolates were also found to represent the most basal locality in this study based on unweighted pair group method with arithmetic mean (UPGMA) clustering analysis and were distinct from other localities based on STRUCTURE V 2.3 analysis. These results support previous reports suggesting that the parthenogenetically reproducing isolates from Japan are another species. Taken together, our results can serve as the foundation for more extensive characterization of population structure and genetic variation among isolates of R. reniformis variants to help discern the impact of alternative processes on genetic connectivity and differentiation in the genetically undercharacterized reniform nematode.