Relationship between Cracking Occurrence and Growth or Fruit Characteristics in ‘Jinok’ and ‘Campbell Early’ Grapes

This study was conducted to analyze the correlations among cracking occurrence, growth, and the fruit characteristics in ‘Jinok’ compared to ‘Campbell Early’ grapes (Vitis labruscana). The flower cluster length and berries of the two cultivars tended to increase slowly after an initial rapid growth at 23 to 50 days after bud burst and at 7 to 28 days after full bloom, respectively. The cracking of ‘Jinok’ and ‘Campbell Early’ grapes occurred 49 and 56 days after full bloom respectively, and the same times coincided with the early stage of fruit maturation when the berry enlargement was moderate. There were fewer cracked berries per cluster in ‘Jinok’ (3.3%) than in ‘Campbell Early’ (8.3%) during the harvest period. There were no statistically significant differences in the shoot length or petiole diameter according to the presence or absence of cracking, and among the fruit characteristics, the cluster with cracked berries had a large number of berries and a thick cluster stalk diameter. As a result of analyzing the relationships among variables through correlation and principal component analyses, it was found that the number of berries (r = 0.780**, r = 0.735**), the berry density (r = 0.778**, r = 0.736**), the cluster width (r = 0.318*, r = 0.608**), and the cluster weight (r = 0.672**, r = 0.621**) were closely correlated with the occurrence of cracking in the two cultivars. Therefore, maintaining an appropriate berry set amount per cluster in consideration of the cluster size will be a cultivation measure that can reduce the occurrence of cracking.