Induction of bud breaking and flowering during paradormancy in apple trees
To establish various apple cultivation systems, we investigated plant growth regulator effects on bud breaking induction and flowering during paradormancy in apple trees. We also examined annual changes of the onset period of dormancy and flower bud differentiation. Our experiments examined 'Snowdrift' crabapple grafted on Marubakaidou apple rootstock. Plant growth regulators were applied by foliar spraying of the whole tree. The application of 600 ppm benzylaminopurine (BA), a synthetic cytokinin, on July 22, 2014 caused bud breaking of 35 buds tree-1: of those, 14 buds flowered. However, BA 600 ppm application on July 8, 18, and 30 and on August 7 and 17, 2015 caused no bud breaking or flowering. When BA 600 ppm was applied on July 1, 8, and 20, 2016, the respective percentages of shoots exhibiting bud breaking were 45, 9, and 4.5%. The later the application, the longer the shoots were when buds broke, which suggests that shorter shoots enter ecodormancy earlier. Furthermore, fluridone, abscisic acid synthesis inhibitor, 1 ppm and BA 600 ppm + fluridone 1 ppm were applied on July 20, 2016. Of all shoots, 20% exhibited bud breaking by BA 600 ppm + fluridone 1 ppm application. The length range of shoots showing bud breaking after BA 600 ppm + fluridone 1 ppm application was more extended than after BA 600 ppm application. Results show that BA combined with fluridone might induce bud breaking during onset of ecodormancy. However, no treatment induced flowering. Considering the estimated date of bud breaking in spring in 'Snowdrift' each year, the onset period of ecodormancy might be affected by the onset period of bud breaking. Nevertheless, no relation was found between the bud breaking period and the flower bud differentiation period.
Watanabe, M., Kogawa, S., Inoda, Y., Kagi, R., Kumagai, H., Murakami, M. and Komori, S. (2018). Induction of bud breaking and flowering during paradormancy in apple trees. Acta Hortic. 1206, 169-174
abscisic acid, benzylaminopurine, cytokinin, fluridone, 'Snowdrift'