TIMING OF CLUSTER THINNING AS A METHOD FOR CROP ADJUSTING AND IT'S IMPACT ON GROWTH. YIELD AND FRUIT QUALITY OF RUBY SEEDLESS GRAPEVINES

This study was carried out to disclose the effect of cluster thinning at
different stages as a method for crop adjusting on growth. yield and fruit
quality of Ruby seedless grapevines. One-quarter of the cluster number on
each vine was removed at different stages of cluster development. thus.
reducing the number of clusters per vine from 32 to 24. Vines were randomly
assigned a date of cluster thinning based on the following stages of cluster
development pro-bloom (PB); full bloom (FB); berry set + one week after
berry set (BS1); two weeks after berry set (BS2); three weeks after berry set
(383) and four weeks after ben'y set (BS4) and unthinned vines (control), on
which 32 clusters were retained through the experiment.
The results showed that the quality of Ruby seedless grapes could be
easily improved by the cluster thinning. The early thinning of clusters pre—
blcom (PB) ensured the best vegetative growth parameters and the highest
bud fertility. However. Vines thinned at one week after berry set (BS1) can be
recommended as the best effective treatment. The slight decrease in the
yield obtained from this treatment could be compensated by improving
physical properties of berries and decreasing percentage of shot bern‘es per
cluster . as well as achieving a highest percentage of TSS. better colouration
and a lower percentage of acidity in the juice.