Effects of Coverlys TF150^® on the Photosynthetic Characteristics of Grape

Grape rain-shelter cultivation is a widely employed practice in China. At present, the most commonly used rain shelter film materials are polyvinyl chloride (PVC), polyethylene (PE), ethylene-vinyl acetate copolymer (EVA), and polyolefin (PO). Coverlys TF150^® is a woven fabric with an internal antifoggy PE coating that has not yet been popularized as a rain shelter film for grapes in China. To investigate the effects of Coverlys TF150^® on grapes, we measured the microdomain environment, leaf development, and photosynthetic characteristics of 'Miguang' (Vitis vinifera × V. labrusca) under rain-shelter cultivation and performed transcriptome analysis. The results showed that Coverlys TF150^® significantly reduced (p < 0.05) the light intensity, temperature, and humidity compared with PO film, increased the chlorophyll content and leaf thickness (particularly palisade tissue thickness), and increased stomatal density and stomatal opening from 10:00 to 14:00. Coverlys TF150^® was observed to improve the maximum efficiency of photosystem II (F_v/F_m), photochemical quenching (qP), the electron transfer rate (ETR), and the actual photochemical efficiency (Φ_PSII) from 10:00 to 14:00. Moreover, the net photosynthetic rate (P_n), intercellular CO₂ concentration (C_i), stomatal conductance (G_s), and transpiration rate (T_r) of grape leaves significantly increased (p < 0.05) from 10:00 to 14:00. RNA-Seq analysis of the grape leaves at 8:00, 10:00, and 12:00 revealed 1388, 1562, and 1436 differential genes at these points in time, respectively. KEGG enrichment analysis showed the occurrence of protein processing in the endoplasmic reticulum. Plant hormone signal transduction and plant-pathogen interaction were identified as the metabolic pathways with the highest differential gene expression enrichment. The psbA encoding D1 protein was significantly up-regulated in both CO10vsPO10 and CO12vsPO12, while the sHSPs family genes were significantly down-regulated in all time periods, and thus may play an important role in the maintenance of the photosystem II (PSII) activity in grape leaves under Coverlys TF150^®. Compared with PO film, the PSI-related gene psaB was up-regulated, indicating the ability of Coverlys TF150^® to better maintain PSI activity. Compared with PO film, the abolic acid receptacle-associated gene PYL1 was down-regulated at all time periods under the Coverlys TF150^® treatment, while PP2C47 was significantly up-regulated in CO10vsPO10 and CO12vsPO12, inducing stomatal closure. The results reveal that Coverlys TF150^® alleviates the stress of high temperature and strong light compared with PO film, improves the photosynthetic capacity of grape leaves, and reduces the midday depression of photosynthesis.