Effects of Rootstock and Disbudding on the Growth and Quality of Persimmon (Diospyros kaki Thunb.) Fruit

The growth and quality of the fruit from adult ‘Fuyu’ and ‘Hiratanenashi’ Japanese persimmon (Diospyros kaki Thunb.) trees that were grafted onto D. kaki seedlings (S), Rootstock-a (R-a), ‘MKR1’, and own-rooted (O-R) trees planted in February 2003 were observed from 2015 to 2021, when almost all of the trees entered stable, high-productive phases and the fruit quality was stable. The trees that were grafted onto ‘MKR1’ were still dwarfed but produced fruit efficiently. After disbudding took place, in the first half of stage I of the double sigmoid growth curve there was a certain period of time when the fruit of the ‘Hiratanenashi’ trees that were grafted onto ‘MKR1’ was lighter than the trees that had been grafted onto S. However, in the second half of stage I, the fruit of the former was heavier than that of the latter, and the flesh cells of the former were larger than that of the latter. In stage II and III, the fruit of the latter grew faster and became significantly heavier just before the harvest. The fruit growth of the ‘Fuyu’ trees that were grafted onto R-a was retarded compared to the growth of trees that were grafted onto ‘MKR1’ throughout most of the growing period. Heavy disbudding (HD) effectively increased the fruit weight of the ‘Hiratanenashi’ trees that were grafted onto ‘MKR1’ in a certain time period in stage I and in stage III compared to normal disbudding. HD also improved the fruit growth of the ‘Fuyu’ trees that were grafted onto ‘MKR1’, although this was not as effective as the ‘Hiratanenashi’ fruit growth. The weight of the harvested ‘Fuyu’ trees’ fruit increased in the following order: R-a, ‘MKR1’, O-R, and S. The ‘Hiratanenashi’ trees that were grafted onto ‘MKR1’ had the lightest fruit among the rootstocks, but the HD treatment for the trees that had been grafted onto ‘MKR1’ increased the fruit weight, and the difference disappeared. The soluble solids concentration of ‘Fuyu’ fruit was the highest in ‘MKR1’ and the lowest in R-a. ‘Hiratanenashi’ fruit had the highest concentration of soluble solids in S and the lowest concentration in O-R. The level of firmness of ‘Fuyu’ fruit flesh was the hardest in ‘MKR1’ and the softest in R-a, whereas the level of firmness of ‘Hiratanenashi’ fruit was the same among the rootstocks. Although the a* value of ‘Fuyu’ fruit skin color was the same among the rootstocks, the a* value skin color of ‘Hiratanenashi’ fruit was the highest in ‘MKR1’ and R-a and the lowest in S. These results suggest