Optimization of GA3 concentration for improved bunch and berry quality in grape cv. Crimson Seedless (Vitis vinifera L)

Crimson Seedless is a coloured seedless grape, gaining popularity in India for its attractive colour, bunch and berry quality with better shelf life. In cultivation of any seedless grape variety, application of GA3 at different stages is very much essential to produce good quality berries and bunches. However, this variety is highly sensitive to excess application of GA3 and practicing GA3 schedule similar to that of Thompson Seedless grapes adversely affects bunch quality. Hence, there was a need to standardize mild dose of GA3 just for rachis elongation which will help to reduce bunch compactness to a greater extent. Hence, an experiment was initiated to standardize concentration of GA3 for rachis elongation of Crimson Seedless grapes. Three different concentrations of GA3 {viz., 5 ppm (T1), 7.5 ppm (T2) and 10 ppm (T3)} were sprayed during pre bloom stage and compared with unsprayed control (T4). Among different treatments, pre-bloom spray of GA3@5 ppm could produce less compact bunches with highest average bunch weight, berry weight, berry length and TSS. However, bunches sprayed with 7.5 ppm and 10 ppm GA3 could also produce good quality bunches average berry weight and TSS was less. Because of severe coiling of rachis at 7.5 ppm and 10 ppm GA3 spraying, bunches were too straggly compared to spraying of 5 ppm GA3. The control bunches without GA3 spray produced very compact clusters with less average bunch weight, berry weight, berry diameter and berry length.