DNA markers associated with resistance to Java']Javanese root-knot nematode in soybean

Javanese root-knot nematode [Meloidogyne javanica (Treub) Chitwood) (Mj) is a pathogen of soybean [Glycine max (L). Merr.] in the southern USA. Although breeding for root-knot nematode resistance is an important objective in many plant breeding programs, progress in selection for nematode resistant lines is hampered by laborious screening procedures. The inheritance of resistance to Mj is quantitative and has a moderate to high heritability (0.48-0.76). The objectives of this study were to use restriction fragment length polymorphism (RFLP) markers to identify quantitative trait loci (QTL) conditioning resistance to Mj and to determine the genomic location and the relative contribution to resistance of each QTL. Eighty-four F-2 progeny from a cross between ''CNS'' and a root-knot nematode resistant soybean plant introduction, PI230977, were used to map 86 RFLP markers and three morphological traits. The 89 markers converged on 18 linkage groups spanning a total of 1053 centimorgan (cM). Sixty-eight of the 84 F-2:3 families were assayed for Mj galling in the greenhouse. Analysis of variance and interval mapping were used to identify QTL associated with galling. Two QTL with alleles derived from PI230977 conditioning resistance to Mj were identified on two Linkage Groups (LG). Marker B212-1 on LG-F accounted for 46% of the variation in gall number, whereas A725-2 on LG-D1 accounted for 13%. The additive model best fit the data, and together the two markers accounted for 54% of the variation in gall number. Marker B212-1 is within a cluster of seven other disease resistance loci that span a 5- to 10-cM region on LG-F.