ISHS Acta Horticulturae 587: International Symposium on Asian Pears, Commemorating the 100th Anniversary of Nijisseiki Pear
REGULATION OF ENDODORMANCY IN JAPANESE PEAR |
| Authors: | F. Tamura, K. Tanabe, A. Itai |
| Keywords: | Pyrus species, chilling accumulation, budbreak, abscisic acid, gibberellin, protein. |
| Abstract:
This paper describes recent studies of bud endodormancy in Japanese pear. In the first study we estimated chilling requirements of wild pear species and Japanese pear cultivars. P. fauriei had the lowest chilling requirement among the wild pear species, while P. aromatica and P. communis had the highest. In the major Japanese pear cultivars, ‘Housui’ had the lowest chilling requirement, followed by ‘Kousui’, ‘Nijisseiki’ and ‘Niitaka’, and ‘Shinsetsu’ and ‘Shinsui’. In the second study, changes in endogenous abscisic acid (ABA) and gibberellin (GAs) and the effect of ABA injection on percentage bud break in the ‘Nijisseiki’ pear buds were determined. Bud dormancy was induced by injection of ABA in early autumn. Budbreak on the shoots accumulating 200 and 600 chill units (CU) was inhibited by injection of ABA, whereas injection of ABA did not affect budbreak on the shoots accumulating 800 and 1,200 CU. ABA level in buds decreased with increases in chilling accumulation up to 800 CU. A rapid increase in GAs was detected in the buds after 1,200 CU. In the third study, effects of hydrogen cyanamide, garlic paste and high temperatures on breaking bud dormancy were tested. High temperature (45oC for 4 hr) showed the strongest effect of breaking endodormancy of ‘Nijisseiki’ pear among the treatments. In the fourth study, the effect of actinomycin D on budbreak was tested with high temperature treatment. Changes in the protein profiles of the pear buds were analyzed during breaking dormancy by chilling and high temperature. Budbreak induced by high temperature was reversed by pre-treatment with, whereas post-treatment with Actinomycin D did not do so. The quantities of nine cold-induced proteins (CIPs) increased in the buds with chilling accumulation. The isoelectric point of the 19-KDa CIPs was shifted to the basic-side by high temperature treatment as well as by chilling. | |
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