Response of Fruit Growth and Quality to the Spray of Plant Growth Regulator in Yellow-fleshed Kiwifruits

This study was conducted to investigate the effect of the number of spray applications of a plant extract (Benefits (R) PZ) on the growth and quality of kiwifruit. Single, double, and triple spray applications from two weeks to four weeks after anthesis were compared with a control to test 'Sweet Gold' and 'Jecy Gold' which are major varieties with yellow -flesh grown on Jeju Island. In both cultivars, as the number of spray applications was increased, the fruit size increased, as did the fruit length, diameter, and fruit weight, with deterioration of fruit quality parameters such as the dry matter and flesh color not observed. The increased fruit size was associated mainly with the enlargement of the fruit core and outer pericarp tissues, which in turn was associated with increases in both the cell number and size of fruit core tissue, but also with increases in the number of small cells and the sizes of the large cells from the outer pericarp tissue. There was little effect of the plant growth regulator spray treatments on the fruit quality during room temperature storage, and yellow -flesh coloration tended to be even higher in the treated than in the untreated case. The starch contents were not affected by plant growth regulator spraying at 150 days after full bloom (DAF), at which starch accumulation was maximized, in both cultivars. However, As the treatment period prolonged, differences began to emerge and continued to widen over time. The content of soluble sugars began to increase rapidly at 120 days DAF and showed differences between treatments around 170-180 DAF, but the tendency of those responses was not distinct depending on cultivars. Consequently, the findings here indicated that the plant extract (Benefits (R) PZ) spray contributed to an increase in the fruit size and affected the cell number and size, with no detrimental side -effects on the fruit quality. The response of starch and soluble sugars content to spraying differed between the two cultivars, and no distinct tendency was observed.