Photosynthetic Activity and Soluble Carbohydrate Content Induced by the Cold Acclimation Affect Frost Tolerance and Resistance to Microdochium nivale of Androgenic Festulolium Genotypes

The aim of the experiment was to verify whether changes in photosynthetic activity measured by means of chlorophyll fluorescence techniques and soluble carbohydrate level induced during pre-hardening and cold acclimation in androgenic forms of Festulolium are related to their winter hardiness and pathogen resistance. The study was performed on six androgenic genotypes of Festulolium, which differ in their degrees of winter hardiness. The chlorophyll fluorescence parameters and sugar content were measured in the control plants, pre-hardened at 12 degrees C and cold-acclimated at 2 degrees C. Cold acclimation at 2 degrees C, preceded by pre-hardening at 12 degrees C, induced a decline in maximum PSII quantum efficiency (F(v)/F(m)) and in non-photochemical quenching (NPQ). Exposure to 2 degrees C also resulted in reduced efficiency of energy conversion in photochemical processes (q(p)). The soluble carbohydrate amount increased in the susceptible genotypes and was associated with a decline in NPQ and current quantum yield of PSII (phi(PSII)). In resistant plants, a decrease in the sugar content was observed, which could be explained by their consumption in metabolic processes initiated during cold acclimation. The changes in sugar content were associated with a decline in NPQ and q(p).