Effect of gibberellic acid, CPPU and harvest time on browning of Vitis vinifera L. 'Regal Seedless': pre-cold storage and post-cold storage quality factors

J.H. Avenant
The aim of this study was to investigate gibberellic acid (GA3) and N-(2-Chloro-4-pyridyl)-N-phenylurea (CPPU) treatments which can reduce or eliminate browning of white table grape cultivars. In this study the response of the bunches to the GA3 and CPPU application had on the quality of the grapes was determined. Data with regard to pre-cold storage quality, as well as post-cold storage quality of the grapes, with the emphasis on berry quality, were collected. During two consecutive seasons (2008/09 and 2009/10), this study was conducted on mature 'Regal Seedless' with Ramsey as rootstock, on two commercial farms in the Berg River Valley. Tweety treatment combinations of GA3 (no GA3, 10, 20, 30 and 40 ppm) and CPPU (no CPPU, 1, 2 and 4 ppm) were applied and replicated eight times. Grapes from each treatment were harvested at 16 °Brix, 20 °Brix and 24 °Brix. After packing as for export, cartons were stored at -0.5°C for 8 weeks plus 4 days at 7.5°C, before browning and standard export quality evaluation. Pre-cold storage data with regard to berry size, juice quality and total phenol content were also collected. Berry mass was significantly improved by GA3 and CPPU treatments, while berry mass decreased with harvest time. Increasing dosages of GA3 and CPPU resulted in a further increase in berry mass. A delay in ripening was induced with an increased concentration of both GA3 and CPPU treatments. CPPU treatment significantly increased TTA, while pH and sugar:acid ratio were decreased. Increasing dosages of GA3 resulted in a further decrease in TTA and an increase in pH and sugar:acid ratio. Both GA3 treatments and harvest time had a significant effect on grape quality after cold storage. Berry decay, berry abscission and SO2 damage were significantly increased by GA3 application. Delayed harvest time significantly increased the occurrence of decay and decreased berry split.
Avenant, J.H. (2017). Effect of gibberellic acid, CPPU and harvest time on browning of Vitis vinifera L. 'Regal Seedless': pre-cold storage and post-cold storage quality factors. Acta Hortic. 1157, 373-380
DOI: 10.17660/ActaHortic.2017.1157.52
https://doi.org/10.17660/ActaHortic.2017.1157.52
grape, berry mass, TSS, TTA, pH, berry quality, cold storage, total phenol content
English

Acta Horticulturae