Abstract
Wheat yellow mosaic disease, caused by wheat yellow mosaic virus (WYMV), is transmitted by a soil-borne micro-organism. There have been many outbreaks of WYMV in southwestern Japan since the 1910s. In Hokkaido, the northernmost area of Japan, the first occurrence was reported in 1991. ‘Hokushin’, the leading variety of common wheat in Hokkaido, is susceptible to WYMV, and damage has occurred over a wide area in Hokkaido. We found that the American cultivar ‘Madsen’ was resistant to WYMV in field trials over five years. ELISA tests using an F2 population indicated that a single dominant gene in ‘Madsen’ contributed to the resistance; however, ‘Madsen’ is a late-maturing cultivar, is not tolerant of pre-harvest sprouting, and is susceptible to snow mold. Therefore, we introduced the resistance gene by repeated backcrossing using ‘Madsen’ as the donor parent and ‘Hokushin’ as the recurrent parent, using field selection. This produced four WYMV-resistant BC5F4 generation lines with almost the same agronomic traits as ‘Hokushin’. The resistance gene, YmMD, derived from ‘Madsen’, was mapped on the long arm of chromosome 2D (2DL), between wmc041 and gwm349 using polymorphic SSR markers between ‘Hokushin’ and BCM5F4 lines.
