The effect of heat stress on chlorophyll fluorescence in Pannonian wheat varieties

Abstract

Winter wheat is sensitive to heat stress, which highlights the need for adaptation to hightemperature events to ensure high and stable yields. This study aimed to investigate the chlorophyll fluorescence response of eight wheat varieties from southeastern Europe to heat stress. Heat stress was applied during anthesis and mid-grain filling at 35/25 °C and 38/28 °C day/night for seven days, respectively. The results showed no significant differences in Fv/Fm values between wheat plants grown under control and heat stress during anthesis on the first, second, fifth, and seventh stress days. This absence of high-temperature effect during anthesis indicates that temperatures of 35/25 °C for seven days are insufficient to differentiate wheat variety reactions based on Fv/Fm measurements. However, when temperatures were increased to 38/28 °C during mid-grain filling, a significant variation in Fv/Fm values among the studied wheat varieties was observed. NS 40S and NS Ilina showed a notably slower reduction in Fv/Fm over time under heat stress treatment at mid-grain filling, exhibiting the highest Fv/Fm values on the seventh day. These varieties can be valuable sources of heat stress tolerance and should be considered for further breeding activities under the conditions of southeastern Europe.