Heat tolerance of highbush blueberry is related to the antioxidative enzymes and oxidative protein-repairing enzymes

•It was hypothesized and testified by physiological analysis and field trials that some northern highbush blueberry cultivars such as 'Jersey' were more heat-tolerant than some southern highbush cultivars.•To our knowledge, it is the first report about the oxidative protein repairing genes (TRXs and MSRs) involving heat endurance in plants.•The present study also supplies a reliable method to evaluate the heat tolerance in blueberry based on the expression levels of antioxidative enzymes and oxidative protein-repairing enzymes.

Improving the understanding of the heat-tolerance mechanisms in blueberries (Vaccinium spp.) and screening high heat-tolerant germplasms are critical for the development of this fruit. In the present study, the heat tolerances of the 'Jersey' and 'Diana' cultivars were compared, which represent the northern and southern highbush blueberry cultivars, respectively. The results showed that exposure to high temperature significantly increased the level of oxidative damage in both highbush blueberries. However, oxidative stress induced by high temperature is significantly lower in 'Jersey' than that observed in 'Diana'. The lower level of oxidative stress in 'Jersey' was related to the significantly higher transcript levels of the antioxidative genes and oxidative protein-repairing genes, which may have resulted in the relatively higher semi-lethal high temperature of 'Jersey' (48.30 °C) than that of the heat-sensitive 'Diana'(47.32 °C). The heat susceptibility of 'Diana' was also confirmed by the 3-year field trial, the total death rates of 'Jersey' and 'Diana' were 7.78 and 12.22%, respectively. Therefore, it can be suggested that some northern highbush blueberry cultivars such as 'Jersey' are more heat tolerant than some southern highbush cultivars, and thus suitable for cultivation in lower latitude areas with hot summers.