Mapping soybean rhg2 locus, which confers resistance to soybean cyst nematode race 1 in combination with rhg1 and Rhg4 derived from PI 84751

The soybean cyst nematode (SCN) (Heterodera glycines Ichinohe) is a devastating pest of soybean (Glycine max (L.) Merr.) in the world. Three soybean QTLs for resistance to SCN race 1 were detected through QTL analyses using recombinant inbred lines (RILs) derived from a cross between ‘Tokei 758’ (susceptible) and ‘To-8E’ (resistant to races 1 and 3, derived from ‘PI 84751’ and ‘Gedenshirazu’). Two of the three QTLs appear to be rhg1 and Rhg4 from their locations on the linkage map. The third QTL, detected around Satt359 on chromosome 11, was tentatively identified as rhg2. All RILs resistant to race 1 had all three QTLs. We developed lines carrying the three loci in various combinations, including all and none, from descendants of a cross between ‘NIL-SCN’ (with resistance derived from ‘PI 84751’ in the ‘Natto-shoryu’ background) and ‘Natto-shoryu’. Evaluating these lines in a race 1-infected field in Mito, Ibaraki, showed that resistance to race 1 required all three loci. Through field evaluation of 10 recombinant fixed pairs that we developed, we located the rhg2 locus to an 821 kb-region between SSR markers Sat_123 (=WGSP11_0140) and BARCSOYSSR11_1420 on chromosome 11.