2024 Volume 106 Issue 6 Pages 156-163
A synthetic cytokinin of N6-benzylaminopurine (BAP) can induce female strobili in clusters of male strobili in Japanese black pine. In order to use the hormonal method of BAP to improve seed production in seed orchards in cold regions, we investigated effects of BAP treatments (paste application on winter buds, injection of solution into branches and stems), the timing of treatments (5, 13, 20, 27 September, and 4 October 2013), and the clones (five clones) on female strobilus induction in a seed orchard in Aomori Prefecture, measured the time required for each treatment, and estimated the yields of seed and seedling produced by the best of the treatments. All types of BAP treatment induced female strobili in clusters of male strobili, although their effects varied by type (higher for branch injection and lower for stem injection than paste application, P＜0.05), timing (more effective from mid to late September than earlier and later, P＜0.001), and clone. Stem injection needed the shortest time and the time required for the others was comparable. The percentage of seeds filled and the germination rate of seeds in corns induced by BAP treatment were approximately 65％ of normal seeds. Branch injection, which could most effectively enhance female strobilus induction, would increase 3.8 corns producing 40 seedlings per cluster of male strobili. In a tree, 5 primary branches given the injection could produce 5.8 times as many seedlings as an untreated tree in the seed orchard.
