Influence of low temperature before flowering on the occurrence of unreduced pollen in Japanese persimmon (Diospyros kaki thunb.)

The efficacy of ploidy breeding using unreduced pollen in japanese persimmon (Diospyros kaki Thunb.) is not high because of the low frequency of unreduced pollen in most cultivars. This study was conducted in 2002 and 2003 to determine if the exposure to a low temperature before flowering could enhance the unreduced pollen formation in five cultivars of japanese persimmon including two cultivars that barely produce unreduced pollen under the field condition. The results showed that low-temperature treatment (4 degreesC for 48 hours) increased the occurrence of unreduced pollen at 15 to 17 and 17 to 18 days after the end of the low-temperature treatment in 2002 and 2003, respectively, in all five cultivars tested. Naturally occurring temperatures below 5 degreesC in the field also appeared to enhance the unreduced pollen formation in the cultivars that naturally produce unreduced pollen in the field.