[Effect of girdling and gibberellic application on productivity, yield and contents of endogenous gibberellins in grapes (Vitis vinifera L.) cv. Red Seedless]
1991
San Martin A, Jose Patricio
The cv Red Seedless has shown sensitivity to GA3 in concentrations normally used in other seedless cultivars causing rachis growth distortion, shot berries and affecting sprouting and productivity in next season crop. During 1987/1988, in a vineyard with cv Red Seedless, a trial to evaluate the effect of GA3 on flower thinning and berry growth in combination with trunk girdling was carried out. The GA3 sprayings (3 and 5 ppm) during blooming decreased significantly the percentage of fruit set and the number of berries per rachis cm. It also increased rachis length significantly compared to control. All these effects were positive since they decreased bunch compactness. The GA3 spraying of 10, 15 and 20 ppm after fruit set increased bunch quality through berry size increase. Girdling increased berry weight and diameter. However, the compactness index was higher and soluble solids lower. Despite a higher rachis rigidity, there were no other negative effects observed with GA3 concentration used, during flowering or after fruit set. Endogenous GA activity was detected twice, 10 days before full bloom and 35 DAFB. It followed a similar pattern as seeded cultivars reported in the literature, which would explain the susceptibility of Red Seedless cultivars to GA3 exogenous sprayings
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