Propagation of Wheat Yellow Mosaic Virus in Winter Wheat under Low Temperature Conditions

Abstract

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.