Winter Survival of Cereals Parasitized by Snow Mold

Abstract

In temperate, boreal, and sub-arctic zones, plants such as winter cereals and perennial forages must survive harsh winter conditions, frequently encountering exposure to lethal and sublethal low temperatures. However, in many regions, a deep, persistent snow cover insulates the root and crown zone, maintaining soil temperatures between 0°C and −10°C despite very low ambient temperatures, thereby protecting the plants against low temperature injury. The protracted snow cover creates a dark, humid environment with constant temperatures at or below 0°C, which prevents photosynthesis and drastically slows plant metabolism. These conditions favour development of psychrophilic fungi known as snow molds, which can cause extensive damage to agricultural crops (Figure la-c). The term’ snow mold’ encompasses a number of low temperature diseases involving species of the genera Typhula, Microdochium, Sclerotinia, Pythium, and a complex of low temperature basidiomycetes (LTB) (Laroche et al., 1995). In this article, we outline the nature of snow mold stresses on winter cereals, discuss how resistance to snow molds is induced by hardening, and relate soluble carbohydrate accumulation during the autumn and metabolism during winter to the expression of genetic resistance to snow molds and freezing temperatures.