Identification of Quantitative Trait Loci Conferring Resistance to Rotylenchulus reniformis in Soybean Germplasm from Maturity Groups IV and V

Rotylenchulus reniformis is an economically important nematode of soybean in the southern United States. While host resistance is one of the most effective management strategies, the genetic basis of resistance remains poorly understood, and only a few resistant soybean varieties have been developed. The aim of this study was to utilize a genome-wide association study (GWAS) to identify genomic regions associated with R. reniformis resistance in soybean germplasm from maturity groups IV and V. A panel of 202 soybean accessions was grown under controlled greenhouse conditions in 2024 and 2025. Resistance was assessed using nematode reproduction index (RI = Pf/Pi; Pf, final nematode population density; Pi, initial inoculation density). Best linear unbiased predictions (BLUPs) were estimated across years for GWAS analysis. Significant phenotypic variation for R. reniformis resistance was observed among the soybean accessions, with BLUP-derived RI values displaying a continuous distribution consistent with quantitative inheritance. The GWAS analysis utilizing 34,303 SNP markers identified three significant SNPs associated with resistance on chromosome 18. Allelic analysis revealed that accessions carrying the favorable allele at SNP ss715632853 exhibited reduced nematode reproduction. Candidate gene analysis identified genes associated with plant defense, signaling, and metabolic processes. The chromosome 18 region identified in this study represents a candidate region associated with resistance to R. reniformis, providing molecular resources for soybean improvement. These findings improve the understanding of the genetic basis of R. reniformis resistance and will facilitate the development of resistant soybean varieties through marker-assisted and genomic selection approaches.