Biochemically Induced Variations During Some Phenological Stages in Thompson Seedless Grapevines Grafted on Different Rootstocks

Phenological variation in Thompson Seedless grapevines grafted on different rootstocks and own rootedvines was assessed for two consecutive years and the reasons for such variations were studied throughbiochemical analysis. Uniform and early bud sprouting was recorded in the vines grafted on 110Rrootstock and on own roots, which was attributed to increased peroxidase activity and protein content inthe buds before bud burst. Increased fruitfulness on 110R rootstock and own rooted vines was attributedto the increased phosphorus and protein content of those vines and reduced vegetative vigour measuredin terms of shoot length, cane diameter and pruned biomass. Thompson Seedless grafted on Dogridgerootstock recorded the highest nitrogen content, increased shoot length, cane diameter and increasedpruned biomass attributing to reduced fruitfulness. The highest concentration of phenolic compoundsand amino acids was recorded in the fruits produced on 110R rootstock, while it was least on St. Georgeand own roots. Significant variation in the accumulation pattern of amino acids (especially proline andarginine) was observed, with the least proline/arginine ratio recorded on 110R rootstocks at the time ofharvest, indicating the variation in the days taken for fruit ripening on different rootstocks