Resistance of Winter Rye (Secale cereale L.) to Microdochium nivale Depends on Soluble Carbohydrate Content but not on Abscisic Acid Level

Abstract

Winter rye plants of three Polish inbred lines and cv. Stach differing in Microdochium nivale resistance were studied relating to their frost and pink snow mould tolerance. The plants were prehardened at 12°C for 2weeks and hardened at 2°C for 3weeks. Control plants were grown in the greenhouse at 20°C. Frost resistance expressed as LT50 was determined for leaves and crowns of the hardened and control plants. Cold-hardened were inoculated with mycelium of M. nivale and incubated for 35days at 2°C in the dark. After this time, their pink snow mould resistance was evaluated and expressed as an average regrowth index (ARI). During 13days of pathogenesis, changes in the total soluble carbohydrate (TSC) and ketose content were analysed. Moreover, changes in abscisic acid (ABA) and water content (WC) during 9days of pathogenesis were determined. All analyses were carried out in leaves and crowns of inoculated and non-inoculated (control) plants. Cold acclimation increased frost resistance of the leaves and crowns; however, the crowns were less frost tolerant than the leaves. In the studied lines, there was a negative correlation between frost tolerance of leaves and pink snow mould resistance of plants. Plants of lines more resistant to M. nivale exhibited higher TSC and ketose concentrations in the leaves and crowns as well as lower ABA levels in comparison with the less resistant plants. The role of ABA in the defence response of rye to pink snow mould is still unclear. It seems that ABA concentration does not determine rye resistance to M. nivale, although a higher level of this hormone could decrease it. © 2011 Blackwell Verlag GmbH.