Role of growth regulators in grapes

1. Role of growth regulators in grapes Next End

2. Growth Regulators • The use of growth regulators not only enhances the productivity of vines but also helps to produce quality grapes suitable for exports. • Choice of growth promoters and regulators to be used depends upon the traits desired in the grapes meant for exports. Gibberellic Acid • The amount of GA3 needed to optimize berry size depends on the cultivar and many other factors, but 10 to 60 g/acre is a typical application rate. • The GA3 may be applied once or several times; on some cultivars, multiple in-season applications may increase efficacy. (Cont)…. Next Previous End

3. Application timing is critical and also varies by cultivar. • For many cultivars, the first application is made at , or when berry diameter is about 3-5 mm. • Later applications can delay fruit maturity and inhibit colour development in red- and black-fruited cultivars. • Breeding programs have continuously selected for grapes that produce naturally large berries, so many newer cultivars require less GA3 to attain optimal berry size than older cultivars. • Seeded grapes are generally less responsive to GA3 treatment than seedless grapes. Next Previous End

4. Other Plant Hormones • Forchlorfenuron (CPPU), a synthetic cytokinin, also may be applied at fruit set to increase berry size. • It can be applied by itself, or in combination with GA3, as CPPU and GA3 may have a synergistic effect on berry size. • Berries treated with CPPU tend to develop a rounder shape than non-treated berries. • This compound is highly potent and normally applied at very low doses (1 to 3 mg/L); excessive doses can delay maturity, retard colouring, and have a negative influence on taste. Next Previous End

5. The effects of various growth regulators and growth promoters are as follows- (Source: NRC Grapes) Next Previous End

6. Effects of GA Next Previous End

7. Effects of Ethylene Next Previous End

8. Effects of Cytokinins Previous End