Response mechanism of Shine Muscat grape winter berries quality and sugar metabolism to light quality

【Objective】Exploring the effects of changes in light quality conditions on the quality and sugar metabolism of winter berries in Shine Muscat grapes，providing reference for improving the quality of grape winter berries.【Method】 During the winter berry development stage，Shine Muscat grape plants were treated with LED lights to supplement light， including red light，blue light，and white light. The control group received no supplementary light treatment. Samples were taken once each during the hard berry stage（E-L33），berry swelling stage（E-L35），berry immature stage（EL37），and berry fully mature stage（E-L38）. The longitudinal diameter，single berry weight，total soluble solids content， titratable acid content，fructose content，glucose content，sucrose content，sucrose synthase（SS）activity，sucrose phosphate synthase（SPS）activity，neutral invertase（NI）activity，and relative gene expression levels of berry samples were measured.【Result】White light treatment had great effect on the elongation of berry longitudinal diameter，which was 4.94% significantly higher than the control（P<0.05，the same below）. Red light treatment promoted an increase in soluble solids content in berries，with a significant increase of 11.26% compared to the control during the E-L38 period. Blue light treatment had promoting effect on the reduction of titratable acid content in berries，with a significant decrease of 15.54% compared to the control during the E-L37 period. During the E-L37 and E-L38 periods，red light treatment promoted an increase in fruit fructose content，with significant increases of 11.14% and 22.93% compared to the control respectively. Red light treatment had promoting effect on glucose accumulation berries，with a significant increase of 17.51% compared to the control during the E-L38 period. During the E-L35 and E-L37 periods，the SS activity treated with red light significantly increased by 18.50% and 13.39% compared to the control respectively. During the E-L38 period，red light，blue light，and white light treatments all had promoting effect on SS and SPS activities in berries，and the NI activity of red light treatment was significantly reduced by 17.71% compared to the control. Red light treatment reduced the relative expression levels of VvSS and VvNI genes by 10.54%，20.90%，11.57% and 28.50% respectively compared to the control during the E-L35 and E-L38 periods. During the berry fully mature stage，the relative expression level of VvSPS gene treated with blue light decreased by 22.74% compared to that of the control.【Conclusion】Red light significantly promotes the accumulation of soluble solids，fructose，and glucose contents in the winter berries of Shine Muscat grape，blue light helps to reduce titratable acid content. Red light，blue light and white light all have promote effect on SS and SPS activities during berry ripening. Suitable artificial light sources for supplementary lighting can be chosen based on the requirements of sunlight environment and berry quality for Shine Muscat grape winter berries.