A single QTL on chromosome 6DS derived from a winter wheat cultivar 'OW104' confers resistance to Wheat yellow mosaic virus.

Wheat yellow mosaic (WYM) is a soilborne disease caused by Wheat yellow mosaic virus (WYMV). Symptoms include yellow mosaic coloring of leaves, stunting, and growth inhibition. Severe infection may result in yield loss. WYM is one of the most serious diseases affecting wheat production in East Asia. The most effective control is through breeding resistant cultivars. A winter wheat cultivar, 'OW104', shows little to no symptoms in heavily WYMV-infested fields in Hokkaido, Japan. Here we detected Qym4, a QTL accounting for 45%-57% of WYMV resistance, in the vicinity of the markers Xcfd49, Xbarc183, and Xgpw4357 on wheat chromosome arm 6DS. F3 progenies with 'OW104' allele at Qym4 showed significantly higher resistance than those with 'Hokushin' homozygote or heterozygote. We developed 'Hokushin' near-isogenic lines by backcrossing with 'Hokushin' as the recurrent parent and 'OW104' as the resistance donor. All the WYMV-resistant BC5F1/BC4F1 plants carried 'OW104' allele only at Xcfd49. Our results suggest that the introduction of Qym4 confers resistance to WYMV in winter wheat.

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.