Low temperature-wheat-fungal interactions: A carbohydrate connection

Winter annual and perennial crop species grown in the northern boreal ecosy stem must survive periods of protracted snow cover and low temperatures dur ing the winter. In deep snow regions, plants are susceptible to winter stre sses caused by both snow molds and low temperatures, Therefore, high levels of tolerance to freezing and snow molds are requisite for crops adapted to these regions. Accumulation of soluble carbohydrates in winter wheat durin g the autumn is linked to both hardening and resistance to attack by snow m olds. Snow mold-resistant cultivars accumulate higher levels of carbohydrat e and metabolize them at slower rates than susceptible cultivars, The quant ity and quality of carbohydrates, particularly fructans, remaining in the s pring after snow mold attack appear important for survival of winter wheat. However, the total accumulation of carbohydrates is dependent on the stage of development of the winter cereal plant at the beginning of the winter. Recent research findings have shown that sugars are pivotal metabolic activ ators of the sugar-sensing enzyme, hexokinase, which initiates signal trans duction and activation of numerous metabolic genes including host defense g enes. Thus, an understanding of the metabolism of soluble carbohydrates, pa rticularly fructans, during plant growth, hardening, and snow mold infectio n, is essential to the elucidation of survival mechanisms in plants subject ed to these winter stresses.