Screening and Physiological Mechanism Analysis of Heat-resistant Sweet Potato Varieties

In order to screen and obtain the heat-resistant varieties of sweet potato, four high-quality sweet potato varieties were used as the research objects. The heat resistance evaluation value, SPAD value, hydrogen peroxide (H₂O₂) content, malondialdehyde (MDA) content, catalase (CAT) activity and ascorbate peroxidase (APX) activity of leaves were used as the heat resistance indexes. Then, the effects of high temperature stress on the leaf physiology and antioxidant enzyme activity of sweet potatoes were investigated by comparing the differences of various leaf indexes of four varieties of sweet potatoes under the high temperature stress of 35℃ and 40℃. The results showed that there was no significant change in leaf morphology of the four sweet potato varieties under the high temperature stress of 35℃. Under the high temperature stress of 40℃, the leaves of Longshu 116 and Pushu 23 showed obvious water loss curl, and the SPAD value was significantly lower than that of Jinshan 57 and Guangshu 87. The content of H₂O₂ in leaves was as high as 2.53 nmol·g^-1 and 4.21 nmol·g^-1, which resulted in the increase of CAT and APX activity, and the content of MDA was significantly higher than that of Jinshan 57 and Guangshu 87, which were up to 10.06 nmol·g^-1 and 14.94 nmol·g^-1. According to the comprehensive evaluation, Guangshu 87 was the best sweet potato variety with excellent heat resistance in the the tested varieties, followed by Jinshan 57. The results could provide the heat-resistant variety resources for the planting industry of sweet potato and provide theoretical basis for the breeding of heat-resistant varieties of sweet potato.