Girdling improved berry coloration in summer but suppressed return growth in the following spring in 'Kyoho' grapevines cultivated in the subtropical double cropping system

Abstract

Improving berry skin coloration is one of the major challenges in the tropical and subtropical viticulture. In this paper we aimed to document the effects of girdling at veraison on berry coloration and quality in grapevines on different rootstocks and we assessed the seasonal variations of girdling effects in the subtropical double cropping system. In the first experiment, gird-ling at veraison was tested in 'Kyoho' on 5C rootstocks. In the second experiment, own-rooted 'Kyoho', 5C or 1202C rootstocks were compared. Vines were trained to a horizontal overhead trellis with a single trunk and two short arms. One arm of each vine was girdled at veraison and the other arm served as the control. Girdling at veraison significantly improved skin color of berries from own-rooted vines or 5C rootstocks in the summer cropping cycle but was less effective in the winter cropping cycle. Girdling improved total soluble solids in own-rooted vines in the summer cropping cycle and in vines on 1202C in the winter cropping cycle. Girdling made in the winter cropping cycle did not completely heal until post-bloom in the following spring and reduced length of the fruiting shoot, number of leaves per shoot, and length of inflorescences of the next summer cropping cycle. We concluded that girdling at veraison is a good practice to improve berry color and quality for the summer cropping cycle but is not recommended for the winter cropping cycle.