Positive effect of red/blue light supplementation on the photosynthetic capacity and fruit quality of 'Yanli' strawberry

In order to meet people’s demand for strawberry during winter and early spring, strawberry is usually cultivated in solar greenhouses with forcing cultivation in northern China. However, low light intensities and short-days are the major obstacles that restrict strawberry growth. Therefore, it is crucial to solve the problem of insufficient light in strawberry production. In this study, we established LED facilities to supplement the red/blue light (R/B = 4:1) before sunrise and after sunset in the solar greenhouse. We found that the plant height of the strawberry under supplemental R/B light was 13%−17% higher than that of the control, and the crown diameter of the plants was increased by 1.07−1.38 fold compared with the control for two consecutive years. The net photosynthetic rate of strawberry plants was 19% higher than that of the control. In addition, the strawberry primary fruits’ fresh weight during the stage of full ripeness and the total fruit weight/plant was 18%−24% and 27%−33% higher than that of control for two years, respectively. Fruit soluble solid content and firmness were increased by 1.05−1.21 fold and 1.06−1.18 fold compared with those of control during the two years, respectively. Moreover, we found some differentially expressed genes between red/blue light supplementation and control by RNA-seq, including light-responsive genes (PRR95/LHY/CDF3/CO16/bHLH63/BBX21/PAR1/SIGE) and sucrose metabolism-related genes (SWEET9/BAM1). This study provided a foundation for revealing the mechanism of red/blue light supplementation on photosynthesis and fruit quality of strawberries and could help to improve the cultivation techniques for 'Yanli' strawberry.