Girdling of shoots at flowering reduces shatter in grapevine cv. Malbec

Abstract

Background and Aims: Some grapevine cultivars such as Malbec have unstable yield, due to poor fruitset or fruitlet abscission. The phenomenon is known as ‘shatter’ and this study aims to explore the potential of applying the shoot girdling technique at flowering, to direct the carbohydrate partitioning towards inflorescences and reduce shatter. Methods and Results: Fruitful Malbec shoots were girdled above the apical bunch, below the basal bunch, double girdled or not girdled (Control) during 2017 and 2018. Most vegetative growth parameters were unaffected, but shoots widened and the leaf expansion improved in the fruit zone. Fruitset doubled compared to that of the Control, ovary abortion was reduced, and fruit yield increased, mainly due to a greater number of small berries in the base and double girdled treatments. In addition, base girdling increased TSS per berry, reducing the concentration of phenolic substances in the normal size berries. Girdling effects were consistent during both seasons. Conclusions: Shoot girdling below the basal bunch proved to be effective in reducing shatter. The increase in carbohydrate supply available to the inflorescences during flowering was able to augment their weak sink strength relative to the perennial organs. Significance of the Study: The study contributes to an understanding of the importance of the photoassimilates flow towards inflorescences in reducing shatter and increasing yield in Malbec vines.