Under the background of global warming, this paper explored the physiological mechanism of anthocyanin content in colored wheat in response to high temperature stress in the middle of grain filling, so as to lay a theoretical basis for further coping with the high-quality cultivation of functional colored wheat varieties under climate warming.

The experiment was conducted in Hefei High-tech Agricultural Park in the 2022-2023 and 2023-2024 growing seasons. Six colored wheat varieties with different colors were selected and subjected to high temperature stress treatment (T) for 5 days at the middle stage of filling, with the same materials grown under ambient temperature as the controls (CK).

Under high temperature stress after anthesis, the net photosynthetic rate, stomatal conductance, transpiration rate, relative chlorophyll content (SPAD), dry matter partition, soluble sugar content, sucrose synthase activity, anthocyanin content, anthocyanidin synthase activity, chalcone synthase activity and phenylalanine ammonia-lyase activity of colored wheat were significantly reduced, and the yield of six varieties of colored wheat decreased by 9.10% to 16.94%, 1000-grain weight decreased by 7.84% to 16.94%, and anthocyanin content decreased by 7.18% to 14.17%. The yield, photosynthetic intensity, SPAD value, dry matter partition, soluble sugar content, sucrose synthase activity, anthocyanin content, anthocyanidin synthase activity, chalcone synthase activity, and phenylalanine ammonia-lyase activity of different varieties of colored wheat were: Qinbai 1>Qinlü 3>Qinzi 1>Xinchun 36>Qinhe 2>Qinlan 1, and the anthocyanin content was: Qinhei 2>Xinchun 36>Qinzi 1>Qinlü 3>Qinlan 1>Qinbai 1. The yield of heat-resistant wheat varieties of Qinbai 1, Qinlü 3 and Qinzi 1 decreased significantly less than that of heat-sensitive wheat varieties Qinhei 2, Xinchun 36 and Qinlan 1. The decreases in photosynthetic intensity, SPAD value, dry matter fraction, soluble sugar content, sucrose synthase activity, anthocyanin content, anthocyanidin synthase activity, chalcone synthase activity and phenylalanine ammonia-lyase activity of color wheat varieties Qinhei 2, Xinchun 36 and Qinzi 1 with high anthocyanin content were smaller than those of Qinlü 3, Qinlan 1 and Qinbai 1 with low anthocyanin content. Correlation analysis showed that the yield of each color wheat variety was significantly positively correlated with 1000-grain weight, sucrose content, sucrose synthase activity, flag leaf net photosynthetic rate, stomatal conductance, transpiration rate and SPAD value, anthocyanin content was significantly positively correlated with soluble sugar content, and yield was negatively correlated with anthocyanins, but the correlation was not significant. After high temperature stress after anthesis, the decomposition of sucrose bound to free anthocyanins decreased, and the decomposition of anthocyanins in grains increased, which supplemented the growth and development of wheat.

The antioxidant activity of anthocyanins helped crops resist external stress, and the decline of various indexes of color wheat varieties with higher anthocyanin content was comparable to that of color wheat varieties with lower anthocyanin content under high temperature stress after anthesis, the anthocyanin content was significantly positively correlated with soluble sugar content. In conclusion, the accumulation of anthocyanin content could respond to high temperature stress, reduce the decrease of soluble sugar content, and increase the heat resistance of colored wheat.