1. Role of growth regulators in grapes NextEnd

2. NextPreviousEnd 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)….

3. NextPreviousEnd Application timing is critical and also varies by cultivar. Seeded grapes are generally less responsive to GA3 treatment than seedless grapes. 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. Later applications can delay fruit maturity and inhibit colour development in red- and black-fruited cultivars. For many cultivars, the first application is made at, or when berry diameter is about 3-5 mm.

4. NextPreviousEnd Other Plant Hormones Forchlorfenuron (CPPU), a synthetic cytokinin, also may be applied at fruit set to increase berry size. 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. Berries treated with CPPU tend to develop a rounder shape than non-treated berries. It can be applied by itself, or in combination with GA3, as CPPU and GA3 may have a synergistic effect on berry size.

5. NextPreviousEnd The effects of various growth regulators and growth promoters are as follows- Growth Regulators Concentratio ns Time of ApplicationEffects NAA20 ppm 15-20 ppm 20-25 ppm Spraying at berry formation stage Dipping bunches at sugar formation stage Spraying 10-15 days before harvest Controls flower & berry drop Improves berry cluster Prevents berry drop in transit IBA1000-1500 ppm Dipping of cuttingsPromotes rooting of cuttings 4 CPA10 ppm1st spraying when the berry size is 3 mm dia 2nd spraying when the berry size is 6 mm dia Increases the pedicel thickness (Source: NRC Grapes)

6. NextPreviousEnd Effects of GA ConcentrationsSprayingTime of ApplicationEffects 10-15 ppmSpraying Before floweringIncreases the stalk length of the bunch 20-25 ppm Spraying Bunch dipping Bunch dipping After 25% Capfall 50% Capfall 75% Capfall Thinning of berries 35-40 ppmBunch dippingAfter fruit settingThinning of bunches 30-40 ppm GA + cytokinin Bunch dippingAt 3-4 mm berry sizeIncreases the bunch size 30-40 ppm GA + cytokinin Bunch dippingAt 7-8 mm berry sizeIncreases the bunch size

7. NextPreviousEnd Effects of Ethylene ConcentrationsTime of ApplicationEffects 100 ppm15 days after bud sprout following April pruning Reduces apical shoot growth 200 ppmAt 15-16 leaf stage following April pruning Increases the cane thickness 1000-1500 ppm3-4 days before October pruningInduces leaf drop 250 ppmAt verasion stage or at sugar formation stage Increases the Brix %

8. PreviousEnd Effects of Cytokinins CategoryConcentrationsTime of ApplicationEffects 6 BA10 ppm15-16 leaf stage after April pruning Increases fruit setting in the buds 10 ppmAt 3-4 mm berry size along with 30-40 ppm GA after October pruning Increases the berry size 10 ppmAt 6-7 mm berry size along with 30-40 ppm GA after October pruning Increases the berry size and shape CPPU2 ppm1st application at 3-4 mm berry size along with GA dipping Increase the stalk thickness & berry size, promotes round berry shape and maintains the green colour of the berries