Abstract:

The paper aims to study the effects of different ratios of 6-BA and NAA on sweet potato callus differentiation, subculture multiplication and growth of test-tube seedlings after transplanting, and to establish an efficient system for virus-free in vitro tip meristem culture and rapid propagation technology. Four widely cultivated sweet potato cultivars, ‘Yanshu 25’, ‘Pushu 32’, ‘Longshu 9’ and ‘Shangshu 19’, were used for this experiment. Six 6-BA/NAA concentration ratios were added to MS medium to prepare the induction differentiation medium and the subculture multiplication medium. The callus differentiation rate of tip meristem, seedling formation rate, diameter of callus tissue and number of leaves were investigated, and the differences in survival rate of test-tube plantlets after transplanting, number of leaves, plant height and basal stem thickness were investigated as well to explore the optimal formulations for the callus differentiation, subculture multiplication, and the growth of test-tube seedlings after transplanting. The highest callus differentiation rate of ‘Yanshu 25’ and ‘Pushu 32’ was obtained at A4 treatment (1.5 mg/L 6-BA+ 0.2 mg/L NAA), and the highest callus differentiation rate of ‘Longshu 9’ and ‘Shangshu 19’ was obtained at A3 treatment (1.5 mg/L 6-BA+ 0.2 mg/L NAA). ‘Yanshu 25’ showed better growth in subculture multiplication culture, had a higher survival rate and grew faster in B4 treatment (0.5 mg/L 6-BA+ 0.4 mg/L NAA) than others. The optimal medium for ‘Pushu 32’, ‘Longshu 9’ and ‘Shangshu 19’ was determined as B3 treatment (0.5 mg/L 6-BA+ 0.2 mg/L NAA), with the best growth in subculture multiplication culture, the highest survival rate and the fastest growth after transplanting. In the process of sweet potato callus differentiation and rapid propagation, there were significant differences in the appropriate proportion of 6-BA and NAA for different sweet potato cultivars, and the cultivars characteristics should be fully considered in the actual production.

Key words: sweet potato, stem tip culture, 6-BA, NAA, seedling percentage, propagation