Association betwen plant age simple and complex carbohydrate accumulation among winter wheat cultivars differing in resistance to snow moulds during acclimation at low temperatures

Exposure of winter wheat to pre-hardening (20şC) and hardening (2şC) growth temperatures for different intervals under controlled environment conditions affected the nature and quantity of simple and complex soluble carbohydrates in six cultivars differing in resistance to snow mould. The highest levels of total simple sugars were observed following exposure of plants to hardening temperatures for one week followed by a stabilization or decline following 3 and 6 weeks exposure to 2şC. Fructan levels increased rapidly following 3 and 6 weeks exposure to 2şC. In younger plants grown for 2 weeks at 20şC and hardened for 6 weeks, 10–37% (ave. 20%) of crown dry weights existed as fructans compared with 24–47% (ave. 39%) in crowns of older plants grown for 6 weeks at 20°C and similarly hardened. Fructans comprised 75–82% of all soluble carbohydrates regardless of plant age prior to hardening. The average degree of polymerization increased from DP3-4 following 1 week hardening to DP9-11 following 6 weeks hardening and was significantly higher in hardened older plants than in hardened young plants. These results are discussed in relation to the form of snow mould resistance that increases with plant age in winter cereals.