Effects of Exogenous epi-brassinolid, zinc and boron foliar nutrition on fruit development and ripening of grape (Vitis vinifera L. clv. 'Khalili')

This study was carried out in a commercial vineyard in Bavanat region, located in north of Fars province in Iran, during 2013 and 2014. To investigate the effects of epibrassinolide (Epi-BL) at (0, 0.2 and 0.4 mg L−1), aqueous solution of zinc sulfate (ZnSO4·7H2O) (0 and 2 g.L−1) and boric acid (0 and 0.5 g L−1). Epibrassinolide (Epi-BL) applied at three times pre bloom, bloom (50% calyptra [caps] off) and before ve´raison (50% berries color change) stages. Foliar spray of zinc and boron done approximately two weeks before and with the ten days' interval at the start of blooming on yield, berry number, seed number, pollen germination and fruit set. Results showed that poor fruitset, fruitlet abscission and parthenocarpic are major factors for low productivity in Khalili cultivar in the experimental region. Application of epibrassinolide improved the yield by promoting the cluster length, berry length and berry weight. Application of zinc and boron both together induced berry weight. Boron foliar application had significant effects on berry number per cluster. Foliar application of epibrassinolide increased the efficiency of zinc and boron foliar application on increment of fruitset and yield per vine. Foliar application of 0.4 mg L−1 epibrassinolide and foliar sprays of 2 gL−1 zinc sulfate and 0.5 g L−1 boric acid had the highest impact on chemical and reproductive characteristics and fruitset percentage.