ISHS Acta Horticulturae 689: VII International Symposium on Grapevine Physiology and Biotechnology
PHYSIOLOGICAL RESPONSES OF MINIMAL PRUNING SYSTEMS TO GIBBERELLIC ACID |
| Authors: | K.M. Weyand, H.R. Schultz |
| Keywords: | Vitis vinifera, ´Riesling´, minimal pruning, fruit quality, fruit thinning, gibberellic acid, bud fertility, cluster structure, aroma potential, pre-dawn leaf water potential |
| Abstract:
Minimal pruning systems (MP) can have excessive yields which when combined with cool climate and fertile soils, often causes delayed fruit maturity. The use of gibberellic acid (GA3) was examined to control yield but retain the positive aspects of MP fruit, i.e. loose clusters and small berries. Field experiments were conducted in 2002 and 2003 at Geisenheim, Germany with Vitis vinifera ‘Riesling,’ where GA3 was applied at 500 L ha-1 at a concentration of 50 ppm during bloom. The application of GA3 decreased yield and must/wine quality in 2002 depending on the exact stage of bloom it was applied (50 or 80% capfall). Via carry-over effects on bud-fertility and a second bloom-time application yield decreased further and wine quality increased in 2003. No difference in shoot number per vine was observed between GA3-treated and control vines in 2002 and 2003, while cluster-number was significantly lower in GA3-MP vines. The use of GA3 partly caused an increase in cluster compactness in 2002, but this effect was absent in 2003 and the MP vines retained their characteristic small berry size and loose clusters. Irrespective of yield, total glycoside pool size (G-G) in berries determined with the Glycosyl-glucose-assay showed more G-G g-1 berry fresh weight (BFW) at harvest for the GA3 treated vines both years, albeit not always significant. The reduction in yield through the application of GA3 resulted in higher pre-dawn leaf water potentials for most of the season in 2003 at two different vineyard sites. Results give an overview about the potential and possibilities of using GA3 applications on MP-systems as a means to improve fruit quality. | |
Download Adobe Acrobat Reader (free software to read PDF files) | |
