Interactive effects of 6-BA, GA4+7 and prohexadione-calcium on ‘Gala’ apples

Abstract

Gibberellic acid (GA 4+7) and the cytokinin 6-benzyladenine (6-BA) are used during bloom and fruit set to reduce russeting and improve typiness of select apple cultivars. The gibberellin synthesis inhibitor prohexadionecalcium (P-Ca) is used at the same developmental stage to reduce vegetative growth and susceptibility to fireblight. The use of GA 4+7 /6-BA for enhancing the typiness of Gala apples and the interaction of GA 4+7 /6-BA and P-Ca was investigated in a 2-yr experiment on mature Royal Gala/Bud 9 trees. Six treatments were imposed: (i) untreated control; (ii) 5.5 mg L −1 of GA 4+7 and 6-BA; (iii) 11 mg L −1 of GA 4+7 and 6-BA; (iv) 21 mg L −1 of GA 4+7 and 6-BA; (v) 123 mg L −1 P-Ca; and (vi) a tank mixture of 21 mg L −1 GA 4+7 /6-BA and 123 mg L −1 P-Ca. Trees treated with P-Ca had 21%-45% less growth than the untreated trees or trees treated with GA 4+7 /6-BA. In one of two years, the addition of GA 4+7 and 6-BA tank-mixed with P-Ca reduced the efficacy of P-Ca on shoot growth. GA 4+7 /6-BA decreased soluble solids and fruit firmness in 1 yr, suggesting a delay in fruit maturity. P-Ca alone reduced scarf skin by 7%-10%; however, this effect was negated when combined with GA 4+7 + 6-BA in one of the two years. GA 4+7 + 6-BA increased fruit typiness and length to diameter ratios.

Improving feathering in different nursery apple trees by plant growth regulators

“…The reduction of main trunk growth was observed further up the growing season when the feathers were already developed and could be by the com-petition for nutrients and carbohydrates with the feathers. Vegetative growth control by P-Ca in the present study was consistent with other studies where, P-Ca decreased shoot growth on apples (DUYVELSHOFF; CLINE, 2013) and pears (CARRA et al, 2016;2017). Furthermore, the growth flush after EVANS et al, 1999).…”

“…According to the same authors, when applied during the early stages of vegetative growth, P-Ca reduces the levels of GA 1 (highly active), accumulating its precursor GA 20 (inactive) in plant tissues. Our results are similar to those found in 'Le Conte' and 'Smith' pear trees cultivated in warm conditions and treated with P-Ca to reduce vegetative growth of adult trees, when a pronounced second growth flush was observed after the complete metabolism of P-CA in plant tissues (CARRA et al, 2016;2017), and consequently a growth resumption due to the rapid metabolism of the accumulated GA 20 (inactive) to GA 1 (active).…”

Uticaj biljnih regulatora rasta na kvalitet i skladišni potencijal plodova jabuke

“…Autori za-klju~uju da ovakav efekat na razvoj dopunske boje mo`e biti iskori{}en za spre~avanje pojave crvenila kod sorti jabuke kod kojih je to nepo`eljno, kao {to je Granny Smith. ProCa mo`e ispoljiti uticaj na smanjenje pojave r|aste prevlake i r|aste prevlake poko`ice ploda (McArtney et al, 2007;Cline, 2017).…”