Effects of supplementary light with different wavelengths on fruit quality of 'Ruidu Xiangyu' grape under promoted cultivation

Abstract

To study the effects of supplemental lighting with ultraviolet (UV), blue and red-blue lights on quality development of grape berries under protected cultivation to promote early maturing, four-year-old vines of 'Ruidu Xiangyu' grape using 'Beta' as rootstock were used in this experiment. The results indicated that blue and ultraviolet lights were poor in greenhouse environment. Compared with the control, blue and ultraviolet lights lasting 6 hours at night significantly accele-rated the increase of berry mass, fruit diameter, sugar content and the decrease of acidity content during the grape development, but the effect of red-blue light was not obvious. At the fruit maturation, berries supplemented with the three types of light were heavier, and those treated with the UV light were the heaviest. Additionally, grape berries supplemented with blue light had the highest glucose, fructose and total sugar contents, while the sugar contents in berries supplemented with UV light was lower than that under blue light and higher than that under the red-blue light. Volatile linalool, geraniol, terpineol and nerol reached their peak contents ear-liest in berries supplemented with blue light during the developmental stage. At fruit maturation, berries supplemented with blue light had the highest linalool and citronellol contents, while those with UV light had the highest geraniol, hexanal and E-2-hexenal contents, and supplemented with red-blue light had lower linalool content than the control. Moreover, supplementary light was also beneficial for the accumulation of volatile aldehydes and ketones. In conclusion, blue supplementary light could accelerate the development of grape berries as their sugar content was highest and main terpenes reached their peak contents earliest.Grape berries supplemented with UV light had the largest single berry mass and most abundant volatile compounds, while red-blue light treatment was not so effective on quality improvement.