MKR1 DWARFING ROOTSTOCK PROMOTES FORMATION OF FLORAL PRIMORDIA OF JAPANESE PERSIMMON 'HIRATANE-NASHI'

We observed floral and leaf bud primordia in the buds of Japanese persimmon ‘Hiratane-nashi’ (Diospyros kaki Thunb.) grafted on several types of rootstocks by using a digital microscope. Seedling stocks and own-rooted trees increased number of leaf bud primordia in the buds, and the buds on these trees continued to grow till the beginning of September. In contrast, after the middle of June, the buds of MKR1 trees almost stopped growing, and floral primordia in the buds increased until late July. The developmental stages of floral and leaf bud primordia stopped after July 15 and August 4, respectively. There were no correlations between longitudinal diameter and number of floral primordia in seedling stocks and own-rooted trees. However, a positive correlation in MKR1 trees and a negative correlation in “Rootstock a” trees were found. These phenomena were considered that the decrease in activity of apical meristems in the axillary buds on MKR1 trees induced the occurrence of flower initiation whereas the increase on the other trees led undifferentiated primordia to leaf bud. Hence, larger buds of seedling stocks, own-rooted trees and “Rootstock a” trees did not always contain more floral primordia.