Fine Mapping a Root Knot Nematode Resistance QTL in Soybean: How Does One QTL Control Two Species of Nematodes?

Root knot nematode (RKN) species are some of the most damaging nematodes found in farm soil, with estimated losses of $30 million/year in the Southeastern USA.  To reduce losses in soybean, breeders have developed lines with resistance to the three major RKN species that infect the plants.  While most of the breeding effort focuses on Southern RKN, Peanut RKN and Javanese RKN are emerging as serious pests due to the low number of resistant soybean lines available for these species.  Using RFLPs, researchers previously mapped a single major QTL that increased resistance to both Peanut and Javanese RKN on chromosome 13.  The aim of this study is to use high throughput molecular markers (SNPs) to fine map the resistance QTL(s) and identify the candidate gene(s) to develop robust SNP markers for marker-assisted selection (MAS).

Bi-parental crosses were made to develop two F₅-derived RIL populations to fine map the Peanut RKN QTL and Javanese RKN QTL using polymorphic SNP markers based on SoySNP50k Infinium Chip data.  QTL mapping results indicate a region of resistance near the SNP marker BARC_1.01_Gm13_26668562 on chromosome 13 for both RKN species.  Sequence data from the soybean reference genome indicate several genes of interest located near the marker.  Candidate genes responsible for the resistance QTL(s) will be confirmed by qRT-PCR.  The results of this research can lead to the identification of functional markers associated with one or both RKN QTLs, which will allow for MAS in breeding soybean lines for resistance to these two RKN species.