Berry-cluster thinning to reduce compactness of ‘Black Star’ table grapes

ABSTRACT: The berry-cluster thinning technique was evaluated at different phenological times to prevent bunch compactness of ‘Black Star’ table grape, a new somatic mutation of ‘Brasil’ grape. The trial was carried out during 2012 and 2013 seaons in a vineyard situated in Marialva, PR, Brazil. Vines were trained in an overhead trellis system and spaced at 3x4m. The randomized block design was used as a statistical model with five replications and five treatments. The following treatments were evaluated: control; brushing prior to anthesis; and berry-cluster thinning at different times, when berries were 3-6, 7-10, or 11-15mm in diameter. The prevalence of bunch compactness was evaluated considering the levels: loose, medium loose, and dense bunches. The main physico-chemical characteristics of grapes and yield were also appraised. The data obtained were submitted to ANOVA, and toTukey’s test at 5% was applied. So, thinning is a mandatory practice to avoid bunch compactness of ‘Black Star’ grapes. The technique has to be performed, preferably, by means of brushing prior to anthesis, and the failure to accomplish this practice at this time, berry-cluster thinning when berries are 11-15mm in diameter can be used