1997 Volume 63 Issue 5 Pages 361-365
The seasonal process of infection and propagation of wheat yellow mosaic virus (WYMV) in winter wheat (Triticum aestivum L.) was studied in a field in Morioka, Japan. In the susceptible winter wheat cultivar Nanbukomugi, WYMV was first detected by ELISA only in roots on November 30, about two months after seeding in a field naturally and seriously infested with the virus. The incidence and concentration of the virus in roots and shoots of Nanbukomugi then increased when temperatures dropped below 5°C and with snow cover, and reached a high level before snow melt. Disease incidence in the cultivar in the same field was 96% when wheats were sown at the usual time. In contrast, in the resistant cultivar Hachimankomugi was asymptomatic and virus incidence was low during the same period. In a cross-transplanting test between infested and non-infested fields, virus infection occurring from mid-October through early November in Nanbukomugi resulted in symptom expression in spring. These results suggest that WYMV, infecting during the conducive period, propagated under low temperature conditions which induced a high virus incidence and concentration in the susceptible cultivar before symptoms were expressed, thus resulting in a high disease incidence.