The present investigation was carried out during 2019 and 2020 seasons to
study the effect of GA3 and some natural plant compounds on growth and fruiting
of Thompson Seedless grapevines. The experiment was arranged in a randomized
complete block design in which the study involved six treatments with
three replications, one vine each.
Pruning wood weight, leaf area and total leaf chlorophyll were significantly
increased by spraying either GA3, humic acid, selenium, turmeric or roselle extracts
compared to water sprayed ones (control). Spraying humic acid, turmeric
or selenium were very effective on improving vegetative growth, yield/vine, and
cluster traits. Moreover, these treatments significantly improved the berry quality
in terms of increasing the berry weight, total soluble solids, reducing sugars of
berries compared to unsprayed ones. The best results were obtained on the vines
that sprayed with 0.1% humic acid or turmeric extract. No significant differences
were obtained among humic acid turmeric or selenium spraying. It could be concluded
that spraying humic turmeric or selenium at 0.1% three times annually
was necessary to get high yield with good cluster and berry quality of Thompson
Seedless grapevines. Moreover, such treatments more effective to overcome the
adverse effect of using GA3 i.e. delay the berry ripening and reducing full coloration
of colored cultivars.