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.Chinquapin (Castanea henryi) is an economically important species of the Castanea genus that produces timber and starch, which are widely distributed in southern China, especially in the Fujian, Zhejiang, and Hunan

Recent Advances in Adventitious Root Formation in Chestnut

“…The application of exogenous auxin during the whole rooting period provided also high rooting percentages in seedlings derived microshoots [ 100 , 112 ]. These results are somehow surprising, as the continuous exposure to exogenous auxin might inhibit the initiation phase of AR [ 22 ].…”

“…These results are somehow surprising, as the continuous exposure to exogenous auxin might inhibit the initiation phase of AR [ 22 ]. Similarly, juvenile microshoots of C. henryi rooted well when they were subjected to the continuous exposure to 7.5 µM IBA, whereas no roots were formed when NAA (naphthalene-acetic acid) was used instead of IBA [ 100 ]. In cuttings of Pinus caribea , IBA treatment also proved to be more effective for rooting than NAA [ 113 ] whereas in Douglas fir stem cuttings specific concentrations of NAA (24.6 mM) or IBA (7.4 mM) provided similar percentages of rooting [ 114 ].…”

“…Indeed, rooting rates of microshoots of C. sativa and C. dentata in the presence of full-strength media were satisfactory [ 98 , 112 ]. In addition, better rooting rates and mean number of roots were achieved in C. henryi microcuttings rooted in full-strength media than in half-strength media [ 100 ]. The quality of rooted plantlets of the clone Maraval ( C. sativa × C. crenata ) was improved by adding ascorbic acid to the rooting medium [ 130 ].…”

“…The quality of rooted plantlets of the clone Maraval ( C. sativa × C. crenata ) was improved by adding ascorbic acid to the rooting medium [ 130 ]. Positive results were achieved in microshoots by using mixtures of liquid medium and inert substrates during the expression phase [ 93 , 100 ]. The effectiveness of the Modified Melin-Norkrans (MMN) media has been recently reported on rooting of chestnut microshoots [ 102 ].…”

“…Acclimation conditions for chestnut plantlets require fog and mist systems to minimize water loss while most stomata are not completely functional [ 89 , 143 ]. For this process to be successful, it requires a high relative humidity (RH), which is progressively lowered to allow the plants to adapt to the new conditions, enabling them to develop a functional water balance [ 33 , 100 ], which usually coincides with the production of new leaves. Irradiance at about 300 µmol m −2 s −1 and CO 2 levels of 700 ppm can improve the survival and growth of the rooted shoots, due to the promotion of the autotrophic behavior [ 142 ].…”