Gibberellic acid (GA3) application at the end of pit ripening: Effect on ripening and storage of two harvests of ‘September Snow’ peach

Abstract

Gibberellic acid (GA3) was applied in the orchard to study its effects on ripening and storage potential of two harvests of ‘September Snow’, a white fleshed, low-acid, freestone, melting type peach. Treatment was applied at the end of pit hardening at a dose of 60mgL−1 a.i. The fruit were harvested twice; on August 23 (first harvest) and on September 1 (second harvest). After harvest, fruit from both harvests were stored at 0°C for 3 and 5 weeks. At harvest, both control and GA3-treated fruit of the first harvest had higher IAD (chlorophyll index of absorbance difference; the ratio 670nm/720nm), higher firmness, and titratable acidity compared to the second harvest, while total soluble solids content were similar in fruit from both harvests. Ethylene levels measured during ripening at 20°C after harvest were higher in the second harvest than the first harvest. During shelf life after harvest, or after storage, first harvest fruit were firmer than second harvest. The GA3 effect on maintaining fruit firmness was greater in the first harvest compared to the second harvest during ripening after harvest and after 3 weeks of storage. Second harvest fruit softened more rapidly than the first harvest during shelf life of harvest and 3 weeks cold storage. Flesh bleeding, flesh browning and gel breakdown indices (collectively termed as chilling injury; CI indices) were either absent, lower or appeared later in shelf life in the first harvest compared to second harvest after 3 weeks cold storage. GA3 application was more effective in the first harvest in reducing flesh bleeding and browning compared to the second harvest. Overall, the data suggest that the time of harvest is critical in determining the storage potential of the ‘September Snow’ peaches, and for optimal effect of GA3. Furthermore, a combination of early harvest and GA3 application at the end of pit hardening can improve the cold storage life of this peach cultivar.