Effects of gibberellins and auxin on fruiting of 'Niagara Rosada' grapes

Abstract

Studies were carried out to establish the effects of exogenous growth regulators on Vitis (Labrusca x vinifera) 'Niagara Rosada' fruiting. The investigations were done in the Jundiaí Research Station, Agronomic Institute State of São Paulo, always using disease-free vineyards of good productivity. The morphological transformations of clusters were studied under the following aspects: weight, length and width of cluster; number of berries; weight, length average and width average of berries; length average/width average ratio of berries; number of seeds; length and diameter of rachis; width of cluster minus berries; length and diameter of secondary rachis. That characteristics were determined at the time of maturity plus the total sugars, total acid, Maturity Index and reducing sugars in samples of all treatments. The experiment was conducted in order to determine the doses that resulted in the most beneficial effects, always using applications by immersion of the inflorescence. In 1970 the experiment consisted of applications of gibberellins and 2-hydroxymethyl-4-chlorophenoxyacetic acid treatments of 5, 10, 25, 50, 100 and 500 ppm; gibberellins 50 ppm plus 2-hydroxymethyl-4-chlorophenoxyacetic acid 50 ppm and nontreated, 11 days after flowering. The effectiveness of 100 ppm of gibberellins after flowering to increase cluster weight, berry number and weight, elongation of secondary rachis was determined. Treatment with gibberellins 50 ppm plus 2-hydroxymethyl-4-chlorophenoxyacetic acid 50 ppm increases cluster weight, berries number and weight. Gibberellins at concentration of 500 ppm stimulated berry elongation but did not benefit other characters. Application of 2-hydroxymetlhyl-4-chlorophenoxyacetic acid after flowering, at the concentrations used did not result in good results in 'Niagara Rosada' fruiting under the conditions studied.