Root transcriptome reveals responses to plastic film mulching and grass cover in wine grape 'Cabernet Sauvignon' root and berry

This study was designed to investigate the influence of grass and film mulching on grape (V. vinifera) fruit quality and root transcriptome. The groundcovers (plastic film and seeds of herba portulacae and E. humifusa Willd) were set or sawn on the ground under wine grape plants ('Cabernet Sauvignon'). Test plots in the control group were treated with clean tillage. Properties of plant biochemicals under covers and grape berry quality were determined after two years. RNA-seq was analyzed for grape roots under different treatments. E. humifusa Willd cover increased plant total N and P; and film mulching increased plant total P and decreased plant total K. Herba portulacae cover decreased berry tannin and increased anthocyanin, soluble solid and titratable acid; E. humifusa Willd cover increased anthocyanin, soluble solid and titratable acid. Film mulching increased the contents of berry total phenols, soluble solid, and decreased titratable acid significantly in comparison with clean tillage. Root RNA-seq showed that there were 1, 0, and 42 differently expressed genes (DEGs) in Herba portulacae, E. humifusa Willd and film cover, compared with clean tillage, respectively. Film mulching increased the expression of root high-affinity nitrate transporter 2.1 (NRT2.1), NRT2.4 and glutamine synthetase, which associated with 'Nitrogen metabolism', and decreased the expression of root small class I/II heat shock proteins. Plastic film mulching increased grapple quality properties via activating N metabolism. Film mulching was a more excellent mulching for improving grape quality than grass cover in Ningxia, China.