<i>Rps</i>8 Maps to a Resistance Gene Rich Region on Soybean Molecular Linkage Group F

Abstract

Phytophthora root and stem rot caused by Phytophthora sojae M.J. Kaufmann &amp; J.W. Gerdemann is a serious disease of soybean [ Glycine max (L.) Merr.] worldwide. Recently, a new locus for resistance to P. sojae , Rps 8, was identified and mapped in two small soybean populations. The objective of this study was to verify the genomic location of Rps 8 in a larger population. One hundred thirty‐eight F 2:3 families from a cross between ‘Williams’ ( rps 8/ rps 8) × PI 399073 ( Rps 8/ Rps 8) were genotyped by simple sequence repeat (SSR) and restriction fragment length polymorphism (RFLP) markers. From this set of families, 138 and 69 were phenotyped with P. sojae races 1 and 25, respectively. The segregation ratio for each race fit a 3:1 resistant:susceptible, confirming that Rps 8 segregated as a single dominant gene. On the basis of linkage analysis with SSR and RFLP markers, Rps 8 was located on molecular linkage group F in this population. This region of the soybean genome contains numerous other resistance gene loci as well as pathogen and pest resistance QTL.