Efficient micropropagation technology for banana seedling production

Abstract:【Objective】Bananas are important as a fresh fruit and staple food in the world and possessgreat economic value. Banana production areas and yields were around 364 thousand hectares and 13.57 million tons in China, respectively, in 2014. The banana industry links banana seedling production, pro-duction materials supply, production marketing and processing, etc., which all play an important role infarmer income and as a society stable. Healthy and strong banana seedlings from tissue culture plantletsplay an important role in banana production in China. However, deficiencies exist in traditional microprop-agation methods for bananas so far, which restricts banana seedling production. The objective of this studyis to build a high efficiency banana micropropagation system for the process including explant collection,initiation and proliferation culture, rooting culture and seedling hardening.【Methods】Conventional variety Musa acuminata Cavendish‘Baxi'was used as the plant material. Healthy and strong banana suckerswere collected as explants. Suckers were cleaned and cut short to a 2 cm×2 cm size, and were then disin-fected with 75% ethanol and 0.1% Hg Cl2. Using the improved sucker treatment method T1, the suckersheathing leaves were removed layer by layer, and then cultured in the induction medium. In the tradition-al method(T2), the cleaned sucker pseudostem was directly cut into two bases and put in the inductionmedium. Inducted buds were observed for two generations. In the proliferation culture, different concentra-tions of 6-BA (B1:2.0 mg;B2:3.0 mg;B3:4.0 mg;B4:5.0 mg;B5:6.0 mg) were used in the proliferationmedium, and subcultured for two generations. The proliferated buds were then counted and growth param-eters were measured. In the rooting system, different sugar concentrations of S1:25 g·L^-1;S2:30 g·L^-1;S3:40 g·L^-1;S4:45 g·L^-1 were used in the rooting medium, and cultured for 40 days, then the growth pa-rameters of the seedling height, roots number and pseudostem diameter were measured. In the seedlinghardening study, three culture media, coconut coir, peat soil and red loam were used, then cultured for twomonths and then detected the parameters of plant height, leaf number, relative chlorophyll and plant biomass, etc.【Results】With the improved sucker treatment method T1, 26.4 and 59.8 buds appeared in the1 stand 2ndgeneration, respectively; while only 2.2 and 6.6 buds appeared with the traditional method T2.The new sucker treatment method T1 improved initiation efficiency 12 times more than the traditionalmethod with 26.4 buds grown in the 1stgeneration. For the proliferation culture, increased 6-BA concen-tration showed more proliferated buds. The increase indexes were 2.73 and 2.42 in the 1 stand 2nd genera-tion, respectively for the B5 treatment; while 2.37 and 2.31 for the B3 treatment. Significant larger numberof buds were grown in B3 than B1 and B2 treatments, and no significant differences between the B3 andB4 treatments. In the rooting study, with increasing sucrose concentration, longer and more roots weregrown, while no significant differences were noted in the S3 and S4 treatments. In the seedling hardeningstudy, with coconut coir treatment, the growth parameters of the leaf numbers, plant height, shoot and rootdry matter were higher than those of the other two treatments, which showed the lowest values in red loam.【Conclusion】The improved sucker treatment method T1 improved initiation efficiency, and shortened 3generations with the same number of buds compared to the traditional method T2. The higher efficacy ofmethod T2 saved suckers and decreased the off-type rate. For the proliferation culture, the 6-BA concen-tration was optimized as 4 mg·L^-1(B4), while the sucrose concentration was screened as 40 g·L^-1(S3) inthe rooting medium. Coconut coir treatment showed the greatest potential in seedling hardening, and pro-motion of coconut coir also benefited healthy banana seedling culture production.