Effect of Flower Bud Type on Calyx Perpetual Fruit Production in 'Niitaka' Pear

This study was carried out to inquire the factor related to the development of calyx perpetual fruit, which made fruit shape deformed and fruit quality worse, and to make a cultivation techniques inhibiting it. The changes of tree growth and the development of calyx perpetual fruit were investigated with spur flower types. In twin flower bud, which was heavier and bigger widely, calyx perpetual fruit production was higher than in single flower bud. Especially, calyx perpetual fruit production was more severe in fruits set on sub-flower cluster of twin flower bud. In mineral contents of flower bud, twin flower bud showed higher nitrogen content and lower phosphorous, potassium, calcium content than single flower bud. IAA, t-zeatin and ABA contents in bud from 110 to 7 days after full bloom were higher in twin flower bud than single flower bud. IAA content was increased, t-zeatin content was constant, and ABA content was decreased up to full bloom in both buds. Consequently, the change and difference of plant hormone affects on budding, flowering, further more calyx perpetual fruitlet production.