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Reniform nematode (Rotylenchulus reniformis, Linford and Oliveira) is a sedentary, semi-endoparasite that infects a wide range of plant hosts and is one of the top three nematode pathogens affecting soybean in the southeastern United States. Previous studies have linked resistance to reniform nematode in soybean to two quantitative trait loci on chromosomes 11 and 18. A Kompetitive Allele-Specific PCR (KASP) assay was designed using SNP markers within these two regions to distinguish reniform nematode-resistant soybean based on genotype. A collection of 44 soybean plant introductions with resistant phenotype to reniform nematode and 40 susceptible soybean lines were genotyped at the two target loci to validate the KASP assay design. Of the 44 observed resistant lines, two carried the susceptible genotype; PI 438489B at the locus on chromosome 18 and PI 495017C on chromosome 11. Of the 40 observed susceptible soybean lines, only 25 had the expected susceptible genotype at the loci on chromosome 18 and 13 on chromosome 11. Our KASP assay was 68% accurate in predicting the phenotype of 84 soybean accessions based on their genotype at the SNP marker on chromosome 18 and 83% accurate at chromosome 11. These results indicate a moderate correlation of soybean SNP markers GlyREN18_46 and GlyREN11_190 with reniform nematode resistance. Further research is required to improve the accuracy of KASP assays to predict soybean response to reniform nematode, particularly host susceptibility. [ABSTRACT FROM AUTHOR]

Reniform nematode (Rotylenchulus reniformis) is a yield-limiting pathogen of soybean (Glycine max) in the southeastern region of the United States. A population of 250 recombinant inbred lines (RIL) (F2;8) developed from a cross between reniform nematode resistant soybean cultivar Forrest and susceptible cultivar Williams 82 was utilized to identify regions associated with host suitability. A genetic linkage map was constructed using single-nucleotide polymorphism markers generated by genotyping-by-sequencing. The phenotype was measured in the RIL population and resistance was characterized using normalized and transformed nematode reproduction indices in an optimal univariate cluster analysis. Quantitative trait loci (QTL) analysis using normalized phenotype scores identified two QTLs on each arm of chromosome 18 (rrn-1 and rrn-2). The same QTL analysis performed with log10(M transformed phenotype data also identified two QTLs: one on chromosome 18 overlapping the same region in the other analysis {rrn-1), and one on chromosome 11 (rrn-3). While rrn-1 and rm-3 have been reported associated with reduced reproduction of reniform nematode, this is the first report of the rrn-2 region associated with host suitability to reniform nematode. The resistant parent allele at rrn-2 showed an inverse relationship with the resistance phenotype, correlating with an increase in nematode reproduction or host suitability. Several candidate genes within these regions corresponded with host plant defense systems. Interestingly, a characteristic pathogen resistance gene with a leucine-rich repeat was discovered within rrn-2. These genetic markers can be used by soybean breeders in marker-assisted selection to develop lines with resistance to reniform nematode. [ABSTRACT FROM AUTHOR]