Micropropagation of Chinquapin (Castanea henryi) Using Axillary Shoots and Cotyledonary Nodes

Abstract

Castanea henryi is an important woody grain tree species native to China. The objective of the current study was to find the suitable plant growth regulators (PGRs) and the optimal concentrations for direct organogenesis by using axillary shoots and cotyledonary nodes. Seeds were collected from the field, sterilized, and germinated in vitro. Axillary shoots and cotyledonary nodes of 3-week-old seedlings were used as explants. To find the suitable PGR for adventitious shoot induction, 0.5 mg·L–1 6-benzylaminopurine (6-BA), 0.1 mg·L–1 indole-3-acetic acid (IAA), 0.1 mg·L–1 2,4-dichlorophenoxyacetic acid (2,4-D), or 0.1 mg·L–1 1-naphthaleneacetic acid (NAA) was supplemented to Murashige and Skoog (MS) medium containing 0.65% agar and 3% sucrose. A high induction percentage of adventitious shoots (85.67%) was obtained from cotyledonary nodes supplemented with 0.1 mg·L–1 2,4-D. The type of explant influenced shoot proliferation rates and quality. Apical explants produced more and longer shoots than nodal segments. For shoot multiplication, 1 mg·L–1 6-BA + 0.05 mg·L–1 indole-3-butyric acid (IBA) supplemented with MS medium produced 12.33 and 6.25 shoots per explant, respectively, from apical and nodal explants. For shoot elongation and strengthening, 2 mg·L–1 6-BA + 0.05 mg·L–1 IBA supplemented with MS medium was the best combination, producing shoots with a mean length of 3.50 cm, a diameter of 0.46 cm, and about eight leaves per shoot. The greatest rooting of 76.70% and 11.33 roots per shoot was achieved when cultured in MS medium supplemented with 3.5% perlite + 1.5 mg·L–1 IBA. For acclimatization of the rooted plantlets in the greenhouse, a survival rate of 80% was achieved. This protocol—from multiplication to acclimation—is helpful to realize mass propagation of high-quality trees of chinquapin for increasing production and nut quality.