Necrose das gemas latentes da videira Syrah em função do manejo de poda

Abstract

Southeastern Brazil begins to stand out in the national wine scene, the elaboration of fine quality wines, by chance to the use of new technologies of grape production, attracts consumers to the so-called "winter wines", a fact confirmed with the raising of important awards in Brazil and abroad. Currently, what makes possible this change in the traditional cycle of grapevine cultivation is the management of the double pruning, management developed by researchers of the Agricultural Research Company of Minas Gerais (EPAMIG). However, two prunings per year increase labor use and production costs, and may also negatively affect the dynamics of grapevine reserves. In this sense, previous studies of EPAMIG attempted to change the cycle using a single pruning in January, however, the branches formed under this management did not show inflorescences and, consequently, yield. The aim of this work was to discover the causes of infertility of the branches under a single pruning in summer for winter harvest in the Southeast of Brazil. For that, two experiments were installed in a commercial vineyard using cultivars Syrah implanted in 2003 in the town named Três Corações in the estate of Minas Gerais, one in the year of 2015 and another in the year of 2017. The anatomical modifications of latent buds of the grapevine were also analyzed, as well as measurements of the reserve dynamics of the buds and potential fertility. Monthly samples of dormant buds were collected from the branches formed after summer pruning (January) and branches formed after winter pruning (August) (double pruning management). The anatomical evaluations showed that the high incidence of necrosis of the primary bud of the vine, a phenomenon with physiological causes and worldwide occurrence, is responsible for this unproductivity. There was no report of the occurrence of this phenomenon in the Brazilian Southeast. Its incidence reached more than 90% of the primary buds and consequently led to very low potential fertility. Anatomy also revealed details of necrosis of the primary bud. Therefore, this study showed evidence that the lower availability of carbohydrates strongly favors the occurrence of necrosis. In addition, it was found that the occurrence of necrosis within the bud and its progression to the secondary and tertiary axis is the main reason for the total unproductivity in vines submitted to annual single pruning of summer for the winter cycle.