Effects of Abz-E3M, abscisic acid 8’-hydroxylase inhibitor, and PANMe, abscisic acid antagonist, on bud dormancy release of Diospyros spp.

Bud dormancy, during which buds are unable to resume growth even under growth-promoting conditions, is an important adaptive trait for the survival and growth of woody perennials. Bud dormancy is released when buds are exposed to sufficient chilling. In most persimmon (Diospyros kaki) cultivars grown in Japan, bud dormancy is released by the end of December. Previous studies have shown that the abscisic acid (ABA) content of persimmon buds decreases and ABA catabolic activity increases during dormancy release. To further examine the role of ABA metabolic processes on bud dormancy-release regulation, we investigated the effects of Abz-E3M (an inhibitor of ABA 8’-hydroxylase) and PANMe (an ABA receptor antagonist) on bud dormancy release and bud break. We found that the ABA content was higher in buds treated with a combination of ABA and Abz than that in buds treated with ABA alone, suggesting that Abz-E3M could inhibit ABA catabolism in Diospyros spp. We tested the effects of these chemical compounds on dormancy release of persimmon ‘Jiro’, ‘Taiwanshoshi’, and a diploid wild relative of persimmon, D. lotus ‘Kunsenshi’, by assessing the bud break competency of dormant buds in a growth chamber. PANMe treatment slightly accelerated dormancy release. Treatment with ABA alone and ABA combined with Abz-E3M significantly inhibited dormancy release and bud break. These results collectively suggest that ABA catabolism may be an important regulatory pathway controlling dormancy release and bud break in Diospyros spp. Moreover, our results suggest that manipulation of ABA metabolism by these chemicals may have the potential to delay or accelerate the timing of dormancy release, leading to the modulation of bud phenology in spring; field trials are needed to verify this possibility.