Effects of high temperature on the fruit development and sugar concentration in everbearing strawberry cultivars

In everbearing strawberry cultivars, understanding the effects of high temperature is crucial. Long-day everbearing cultivars are promoted for summer and autumn production whereas this is off-season for June-bearing varieties. This study investigated the effects of high temperature on the development and fruit quality of the everbearing cultivars Natsuakari and Dekoruju in a phytotron-simulating summer condition. Both cultivars showed a smaller number of flowering inflorescences at 30°C/25°C (day/night) compared to 20°C/15°C, indicating that flower bud development is sensitive to high temperatures. Fruit set rates were also negatively affected by the higher temperature. Fruit sugar composition of ‘Natsuakari’ fruits showed an increased sucrose concentration during the developmental stage from 75% colored fruit to 100% colored fruit. In the ripe fruit of ‘Natsuakari,’ the sugar content was measured higher due to greater amount of sucrose accumulation, whereas a remarkable decrease in the sucrose concentration was observed at 30°C/25°C temperature compared to 20°C/15°C. These results suggested that summer high temperatures negatively impacted flowering, fruit set, and sucrose content in everbearing cultivars, ultimately leading to reduced fruit production and quality. Additionally, the temperature effects varied between the two cultivars strawberry.