Girdling and grapevine leafroll associated viruses affect berry weight, colour development and accumulation of anthocyanins in 'Crimson Seedless' grapes during maturation and ripening

'Crimson Seedless' grapes (Vitis vinifera L.) do not develop adequate berry colour in different parts of the world and causes serious economic losses to the growers. The role of girdling and different strains of grapevine leafroll associated viruses on berry weight, berry colour development and the accumulation of anthocyanins and flavonols in the skin of 'Crimson Seedless' grape berry was investigated during 2005-2006 and 2006-2007. Girdling increased the berry weight in both virus-free and virus-infected clones compared to their non-girdled counterparts. Virus infected clone 314 (infected with GLRaV-3 + GLRaV-9 + GVA) and clone 306 (infected with GLRaV-3 + GLRaV-5 + GLRaV-9 + GVA) produced berries which were heavier than those from non-girdled virus-free (control) grapevines. Berries from clone 314, clone 306 and girdled virus-free grapevines had similar berry weight. The levels of total anthocyanin and individual anthocyanins in the berry skin were higher in girdled vines and lower in virus-infected clone 314 and clone 306 than control. Berries from clone 314 and clone 306 accumulated similar levels of anthocyanins in the berry skin. Viral infection altered the concentration of cyanidin 3-O-glucoside and malvidin 3-O-glucoside relative to each other in the berry skin. The levels of flavonols such as quercetin 3-O-glucoside and quercetin 3-O-glucuronide in the berry skin were not influenced by girdling and viral infections. In conclusion, girdling and viral infections increased the berry weight of 'Crimson Seedless' grapes. Berry colour and the levels of total and individual anthocyanins in berry skin were enhanced with girdling and reduced with the viral infections.