A comprehensive evaluation of different responses of supplementary light qualities on physiological and biochemical mechanisms of ‘Kyoho’ grape

Abstract

Grape is an economically important fruit crop worldwide, for which light qualities play a diverse role in vineyard growth and development. However, the regulatory mechanisms between different light qualities and the quality of plant growth at the morphophysiological and pomological levels remain unknown. Therefore, in the current study, we studied plant physiological, biochemical and genetical analysis to investigate the response of all seven light qualities, including red (R), blue (B), white (W), 1-red, 1 blue (1R1B), 2-red, 1-blue (2R1B), 1-red, 2-blue (1R2B), and natural (N, was used as control group) to evaluate ‘Kyoho'grape (Vitis labrusca L. × V. vinifera) morphophysiological, pomological traits at light responsive transcriptional pathway, which revealed the possible networking metabolism controlling fruit quality and quantity of grape plant. Our results showed that photosynthetic indicators such as leaf stomata, number of stomata, and longitudinal and transverse diameter of stomata improved under red and blue light qualities as compared to white light. Leaf gas exchange indicators showed that net photosynthetic rate, transpiration rate, intercellular CO2 concentration rate, total conductance to CO2, stomatal conductance, conductance to water vapor, maximal quantum yield of PS (II), actual photochemical quantum efficiency, electron transfer chain, and non-photochemical quantum efficiency improve under blue and red light. Photosynthetic pigments showed that chlorophyll a and b, carotenoid, and total pigment contents improved under blue and red light. Nutrient elements showed that potassium, phosphorous, magnesium, calcium, iron, and zinc contents improved under blue and red light. Morphological and organic acid indicators such as the appearance of fruit shape, firmness, and titratable acidity improved under blue and light. However, there was a notable increment in the total soluble sugar under blue and red light as compared to natural light. The composition of sugar including (sucrose, fructose, glucose) and organic acids (tartaric acid, citric acid, and malic acid) improved under blue and red light (fruits) and showed notable reductions for tartaric acid under blue and red light (leaves) as compared to natural light. Aromatic compounds showed that esters, aldehydes, acetaldehyde, 2-hexenal, ethyl acetate, n-propyl acetate, butanoic acid, ethyl ester, 1-hexanol, 2-ethyl, 2-propanone, and 1‑hydroxyl, improved under blue and red light. Further, changes in enhanced expression of light-responsive genes including VvCRYI, VvCRY2, VvPHYA, VvPHYB, VvCOP1, VvHY5, VvHYH, and VvPIF4 upregulated under blue and red light, while VvPIF3.1 down-regulated as compared to natural light. Also, chlorophyll synthesis-related genes including VvSGR, VvPAO, and VvCHLH upregulated under blue and red light, while VvNYC1, VvPPH, and VvPOR showed noticeable changes under blue and red light as compared to natural light. Interestingly, most of the relative genes were highly expressed in fruits as compared to leaves. Finally, we have established correlation and principal component analysis for indicators in grapes. Current findings provide novel mechanisms by which different responses of supplementary light control the plant fruit quality of grapes.