Variation in the Relationship Among the Cane and Cluster Characters in Thompson Seedless Grape and Its Mutants

Variation in the relationship among cane and cluster characteristics in Thompson Seedless and its mutants, Tas-A-Ganesh and 2A, was assessed with an aim to (a) identify the basis for variations, (b) determine the optimum levels of the attributes of yield and quality, and (c) suggest the means to improve the desired attributes in the three clones of grapes. Variation in the number of clusters/cane, the number of berries, rachis length and brix yield per cluster was highest in 2A, while the brix yield/cane was highest in Thompson Seedless. Pearson correlation coefficients indicated significant variations between the clones in respect of cane diameter, buds broken/cane, brix yield/cluster, clusters/cane, berries/cluster, berry diameter and rachis length/cluster. Multiple linear regression equations involving cane diameter, buds broken/cane, clusters/cane, rachis length/cluster, berries/cluster, berry diameter and cluster compactness could explain the variation in brix yield/cluster to be 69.0, 71.4 and 44.1%, in Thompson Seedless, Tas-A-Ganesh and 2A clones respectively. Cluster compactness had more contribution towards brix yield/cluster in 2A, while cane diameter and the number of broken buds/cane contributed more in Tas-A-Ganesh. Cluster compactness in turn was determined to be 94.9, 80.5 and 32.6%, in Thompson Seedless, Tas-A-Ganesh and clones respectively, by cane diameter, uniformity in bud break, uniformity in flowering rachis length (cm)/cluster, berries/cluster, berry diameter (mm) and clusters/cane together in a multiple regression analysis. These investigations revealed the scope to increase the brix yield/cluster in Thompson Seedless by increasing the total rachis length and retain a larger number of berries/cluster; increase the fruitfulness of buds and removal of unfruitful shoots after forward pruning to increase the brix yield/cane in Tas-A-Ganesh and to elongate the clusters and reduce the number of berries to produce loose to well-filled clusters; and increase the berry diameter in 2A.