Improving vineyard productivity through assessment of bud fruitfulness and bud necrosis

Abstract

The grapevine compound bud contains three or more buds with the primary bud producing the fruiting shoots for the following season. Primary bud necrosis (PBN) is a physiological disorder resulting in the death of the primary bud. Bud dissection used to assess bud fruitfulness and predict yield potential in vineyards has highlighted the incidence of PBN. Without bud dissection, PBN can go undetected as shoots derived from secondary buds produce fewer bunches and these are typically smaller. Consequently, yield potential is not achieved in vineyards affected by PBN. The project aims were to: assess the distribution and extent of PBN, determine timing and development of PBN and recommend appropriate management options for control. This study showed that PBN is a problem in most viticultural regions in Australia. Shiraz is the most susceptible cultivar and PBN occurred around flowering, coinciding with bud differentiation, and increased to the onset of winter. Excessive vigour contributes to high levels of PBN, and is related to the naturally produced growth hormone, gibberellic acid (GA3). Bud position, pruning levels and irrigation influence the incidence of PBN, whereby severe pruning and water stress leads to high PBN. Balanced pruning is required to (1) reduce the incidence of PBN, (2) reduce excessive vigour and (3) reach a desired yield target with satisfactory quality.

Summary

Primary bud necrosis (PBN) occurs in Shiraz around flowering and increases to the onset of winter. Excessive vigour contributes to high levels of PBN. Severe pruning and water stress enhance PBN.