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Acacia seeds grow into big trees: researchers cultivate superior trees, showcasing the hope of Taiwan's forestry in adversity

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Big trees start from a single seed: researchers cultivate superior acacia offspring, carrying out the hope of Taiwan's forestry in adversity

(Continued from previous article) To promote the planting of acacia timber, we must rely on straight, tall, superior acacia mother trees. In recent years, the Taiwan Forestry Research Institute has searched mountains and forests across Taiwan, China, and has successively identified more than 200 handsome, tall, and upright acacia trees as mother trees, aiming to find superior acacia genes. But how can these superior genes be passed down and become competitive tree species for artificial economic forests? A group of silviculture experts at the Taiwan Forestry Research Institute has launched a long breeding challenge for acacia, aiming to anchor Taiwan's forestry and set sail for the international stage.

Collecting scions from mother trees and express-delivering them quickly to Liugui to cultivate descendants

Five years ago, after the Taiwan Forestry Research Institute found superior acacia mother trees in Danda and various places, it collected 5,820 scions from 106 of them. Immediately after collection, the scions were sent to the nursery at the Taiwan Forestry Research Institute's Liugui Research Center for grafting.

When You Hanming, head of the silviculture division at the Taiwan Forestry Research Institute, mentioned this matter, his memory was still fresh. Every time they went to a place to collect seeds and scions, no matter how remote or how high the mountain forest was, as soon as they returned to civilized society, they immediately looked for express delivery services and sent the collected scions by refrigerated shipping. About 3 to 6 parcels were sent from each seed collection site, and each parcel carried dozens of scions as well as earnest expectations, hoping these scions would have a chance to grow into seedlings.

Associate Researcher Cai Jiabin of the Liugui Research Center is responsible for cultivating small acacia mother trees (Photo / Liao Jinghui)

The collected scions were handed over at the Liugui Research Center to Associate Researcher Cai Jiabin, who was responsible for grafting and seedling cultivation. This was important work in the early stage of the acacia breeding program and also the foundation for subsequently establishing a seed orchard and its progeny trials. Before this, Cai Jiabin had been working on eucalyptus breeding. Encouraged by You Hanming, Cai Jiabin took on the research work of seed collection and seedling cultivation for native acacia.

Grafting scions onto rootstocks to replicate superior genes

When these acacia scions collected in the field poured into the Liugui Research Center wave after wave, the nursery suddenly became busy, and Cai Jiabin's capable assistant Lan Meiyu played an important role. Most of these scions were grafted one by one by him onto 2-year-old acacia rootstocks. For him, who ran an orchard and tea garden at home, this work was not unfamiliar, and he handled it with ease.

However, because these scions collected from acacia mother trees came from mother trees that were already advanced in age, the aged branches did not fit tightly enough, and the grafting success rate was below 10%. Lan Meiyu frequently had to keep replacing the rootstocks with new scions, and during the process he also had to observe and record their growth.

Why were these huge superior mother trees in the wild used as sources of scions to cultivate grafted seedlings, rather than being directly sown? Forestry expert Xu Yuanrui said that scions have relatively stable traits, and what grows out is exactly the same as the mother tree. If seeds are collected, it is like children born to humans: after genetic recombination, although each child carries the genes of both parents, their expression differs.

"Once a good mother tree is confirmed, you only need to collect small branches and graft them onto acacia rootstocks. After successful grafting and one year of seedling cultivation, they can be transplanted to forest land, and trees with the same traits as the mother tree will grow," Xu Yuanrui said.

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