Phytohormone additions match explants stimulating adventitious shoot induction in Cyclocarya paliurus (Batal.) Iljinskaja

Abstract

Abstract As an endemic medicinal woody plant in China, Cyclocarya paliurus (Batal.) Iljinskajais is being extensively planted for leaf-use. Operational system of tissue culture mainly depends on explants from short growth season. To extend sampling season, an efficient tissue culture system for nodal stem segments across annual growth seasons has been established in C. paliurus. Explants collected at three stages (March-May, stage I; June-August stage Ⅱ; September-November, stage Ⅲ) were cultured in MS, supplemented with gradient concentrations of 6-benzylademine (BA) (2.0–12.0 mg·L− 1) for shoot induction. The relationships of phytohomones between endogenesis in explants and exogenous addition in medium were also analyzed by using artificial neural networks (ANN) for the optimal concentration of 6-BA addition. The optimal adventitious shoot induction happened on MS supplemented 6-BA with 4.0 mg·L− 1 for stage Ⅰ, 6.0 mg·L− 1 for stage Ⅱ, and 12.0 mg·L− 1 for stage Ⅲ; their induction ratios reached 92.9%, 96.67% and 82.33%, respectively. Regardless of growth stage, adventitious buds occurred on the 20th day when the content of ABA at the bottom versus IAA on the peak. Moreover, high ABA content in explants of C. paliurus (128.49-325.79 ng/g FW) is considered as the main inhibitor for induction. A model constructed by ANN based on a set of validation data, displayed good agreement with observed results. Also, the combination addition (0.5 mg·L− 1 6-BA + 1.5 mg·L− 1 IAB + 0.03 mg·L− 1 TIBA) to MS for shoot multiplication attained 3.20 of multiplication coefficient. Although rooting induction achieved to 66.67% when supplemented 11.0 mg·L− 1 IBA to WPM, no plantlets survived after acclimatization. We speculate that the high 6-BA content for adventitious buds induction could be responsible for lower rooting rate and transplanting failure. Therefore, more efforts should be done to build a feasible tissue culture system in C. paliurus.