Optimization of ‘Zi Dieer’ crabapple micropropagation through proliferation of axillary shoots

Abstract

ABSTRACT: Malus is an important ornamental plant around the world and widely used in commercial production due to its diversity and wide adaptability. ‘Zi Dieer’ crabapple has good adaptability to a wide temperature range (high and low), disease resistance, and high commercial value. To satisfy the market demand, we established ‘Zi Dieer’ crabapple micro-regeneration system for large-scale reproduction. Induced buds were cultured on Murashige and Skoog (MS) medium supplemented with various concentrations of 6-benzylaminopurine (BAP: 0.5, 1.0, 1.5 mg/L) and 1-naphthaleneacetic acid (NAA: 0.05, 0.1, 0.3 mg/L) for 35 days. The highest bud induction rate (93.3%) was observed on MS medium supplemented with 1.0 mg/L BAP and 0.1 mg/L NAA, with average micro-shoot length of 1.32 cm. The germinated buds (1 cm in length) were propagated and cultured on MS medium supplemented with BAP (1.0, 1.5, 2.0 mg/L) and NAA (0.1, 0.3, 0.5 mg/L), after 35 days, on the MS basal medium supplemented with 1.5 mg/L BAP and 0.3 mg/L NAA, the best average number of new shoots is 8.56±0.13 (P<0.05) and good shoot length (4.94±0.09 cm), reproduction coefficient higher than MS medium (0) without PGRs. In order to induce rooting, the shoots (length 2 cm) are inserted in half strength MS (1/2 MS) medium containing 0.1, 0.3 and 0.5 mg/L of 3-indole butyric acid (IBA) or NAA, and 1 g/L activated carbon (AC) was added on the basis of NAA 0.3 mg/L to study the effect of activated carbon on the rooting of crabapple. After 38 days of culture, compared with other treatments, among the explants treated with IBA, the rooting rate was higher in the 1/2 MS medium containing 0.1 mg/L (82.1%), and the highest root number (11.29±0.52) was observed, and the root length was the other treatments 2-3 times. Although, the highest rooting rate was observed on 1/2 MS medium containing 0.1mg/L NAA (87.8 %), but the bottom of these buds formed large callus, which was not conducive to survival, and the root length was short. In summary, a feasible and complete rapid propagation program for ‘Zi Dieer’ crabapple has been developed.