Effects of cultivation measures on coloration of Merlot berry from the eastern foothills of Helan Mountain in Ningxia

To improve the problem of poor coloration of Merlot berry from the eastern foothills of Helan Mountain in Ningxia, the shoot density (8 shoots/m trellis, 12 shoots/m trellis and 16 shoots/m trellis), fruit load (1.0 clusters/shoot, 1.5 clusters/shoot and >2.0 clusters/shoot), canopy height (100 cm, 120 cm and 140 cm), leaf removal timing (early stage of veraison, completion stage of veraison and two weeks post-veraison), and no leaf removal were set, and the contents of phenolic compounds and monomeric anthocyanins in grape berries were measured. The results showed that the contents of total anthocyanins, total phenolics and total tannins in pericarp with 12 shoots/m trellis treatment were 10.19 mg/g, 44.38 mg/g and 19.38 mg/g, respectively, which were significantly higher than those of other treatments (P<0.05). The contents of total anthocyanins, total phenolics and total tannins in pericarp with 1.5 clusters/shoot treatment were 13.40 mg/g, 49.62 mg/g and 25.97 mg/g, respectively, which were significantly higher than those of other treatments (P<0.05). The contents of total anthocyanins, total phenolics and total tannins in pericarp with canopy height 140 cm treatment were 12.63 mg/g, 62.98 mg/g and 22.88 mg/g, respectively, which were significantly higher than those of other treatments (P<0.05). Removing old leaves below the clusters at the early stage of veraison, the contents of total anthocyanins, total phenolics and total tannins in pericarp were significantly higher than those of no leaf removal treatment (P<0.05). Therefore, implementing cultivation practices such as 12 shoots/m trellis, 1.5 clusters/ shoot, canopy height 140 cm, and removing old leaves below the clusters at the early stage of veraison, significantly increased the contents of total anthocyanin, total phenol and total tannin in the berry, effectively improving the poor coloration issue of Merlot berry.