Effects of chilling exposure and heating temperature on bud burst and flowering of 'KU-PP1' peach tree
A new peach cultivar named 'KU-PP1' was bred by crossing Japanese high-chill and Floridian low-chill cultivars for application in earlier forcing culture in Japan. To determine the optimal conditions for forcing culture of this cultivar, the effects of accumulated chilling hours (CH) and heating temperature on bud burst and flowering were examined in this study. The trees exposed to 240, 570, and 850 CH were grown in sunlit growth chambers with controlled temperature maintained at 10, 15, 20 and 25°C. The dates of bud burst and flowering were recorded. In addition, flower size and pollen germination rate were analyzed. Generally, longer chilling exposure and higher heating temperature hastened bud burst and flowering. Although this cultivar requires approximately 500 CH, our findings indicated that heating should be started from longer chilling exposure, such as 850 CH, to accelerate bud burst with lower costs for fuel used in forcing culture. Bud burst and flowering were markedly suppressed in trees exposed to 240 CH; however, the high heating temperatures improved them to some extent. The increase in the heating temperature led to a reduction in flower size, and pollen germination rates were exceedingly low at temperatures above 20°C. Therefore, the avoidance of excessive heating and the provision of appropriate ventilation in the facilities are essential to ensure normal flower development under the forced cropping system.
Beppu, K., Kawashima, Y. and Kataoka, I. (2018). Effects of chilling exposure and heating temperature on bud burst and flowering of 'KU-PP1' peach tree. Acta Hortic. 1229, 229-234
budbreak, flower development, forcing, low chill, Prunus persica