Relationship between Physiological and Ecological Traits and Snow Mold Damage in Winter Wheat Varieties (Triticum aestivum L.)

Snow damage in winter wheat (Triticum aestivum L.), which is mainly caused by snow mold diseases, is influenced by the physiological activity of the plants under the snow. This study was conducted to examine the shoot weight (SW), percentage of crown weight against the shoot weight (crown %), percentage of dry matter (DM %) and freezing tolerance (FT) by measuring median lethal ternperature (LT50) before wintering in the 1992/93 winter season, FT twice in December and in the following March, and snow mold damage in May in the 1993/94 winter season, using 45 winter wheat varieties. Moreover, we attempted to evaluate the changes in SW, DM. FT and etiolated growth (EG) in the 1992/93 winter season, using 10 representative varieties (Table 1). The correlation coefficients before wintering and 70 days after snow cover were significant for SW and DM % but not significant for FT and EG. Moreover, there was no significant correlation between the respective combinations of DM %, FT and EG. However, the relation became significant 70 days after snow cover (Table 2), mainly due to the slower decrease in physiological indicators such as FT and EG in the snow-tolerant varieties (P.I.173438, Niederndorferberg. Haunsberg, Norin 62) that were sensitive to low temperature and exhibited a higher dry matter percentage than the others (Fig.1). Correlations of FT and EG with snow mold damage were not significant before wintering, but became significant 70 days after snow cover (Fig.4, 5). On the other hand, in all the 10 varieties, DM % decreased under snow cover. As a result, a highest correlation between DM % and snow mold damage was recognized both before wintering (r=-0.618) and 70 days after snow cover (r = -0.879 * * * ). Snow-tolerant varieties were characterized by a high DM %, comparatively low FT and upright type with a crown % of around 35%, while freezing-tolerant varieties showed a high DM % and FT and a rosette type with a crown % of nearly 50% (Fig.2, 3).