Response of berries development and quality of Shine Muscat grape to different light qualities

【Objective】The response of berry growth and quality of Shine Muscat grape to different light qualities was studied to provide theoretical basis for improving fruit quality.【Method】In this experiment, the Shine Muscat grape one week after full bloom stage was treated with red, blue and white light for 6 h every night until the berry color totally changed(8 weeks). No supplementary light was as control. The effects of different light qualities on single berry weight, transverse and longitudinal diameters, tartaric acid, malic acid and soluble solids during fruit ripening and picking were analyzed.【Result】There was no great difference in single berry weight and longitudinal diameter between red light, blue light and white light treatment and the control in the early stage of light supplement(1-4 weeks), but the supplementary lighting treatments in the late stage(5-8 weeks) could promote the increase of single berry weight, longitudinal diameter, transverse diameter and soluble solids. The results showed that 6-8 weeks red light treatment had a significant promoting effect on fruit berry diameter(P<0.05, the same below), the increase range was 3.1%-8.1%, and the highest increase appeared in week 7. Blue light supplement for 4-6 weeks significantly promoted the berry longitudinal diameter, with an increase range of 3.8%-5.1%. The highest difference occurred at 6 weeks after light supplement. Supplemental light increased the content of tartaric acid, red light played a positive role in the metabolism of malic acid, and significantly reduced the content of malic acid by 5.1%-23.2%. Supplemental light promotes the sugar-acid ratio of the fruit in the mature stage, and increased 7.5%-20.6% compared with control. Correlation analysis of berry quality indexes at maturity showed that single grain weight, transverse diameter and longitudinal diameter of berry after light supplement treatment were extremely negatively correlated with tartaric acid and malic acid(P<0.01).【Conclusion】Red light, blue light and white light supplement at night during berry development period of Shine Muscat grape promotes the increase of single berry weight, berry longitudinal diameter, transverse diameter, soluble solid content, sugar-acid ratio. Red light plays an active role in malic acid metabolism and promotes malic acid degradation in the later stage of color transformation. It is suggested that blue light should be added in the early stage of berry development to promote berry elongation, and red light should be added in the late stage of berry development to increase soluble solid content, promote malic acid degradation and improve berry quality.