Abstract
•A protocol was developed for the long-term proliferation of the ‘Grand Nain’ cultivar of banana.•6-benzoyladenine was found effective in the proliferation and elongation of shoots.•6-benzoyladenine and auxin developed structurally superior anatomical features in the in vitro leaves.•6-benzoyladenine and auxin combination increased biomass and photosynthetic pigments in leaves.•The system could be used for mass and sustainable production of the ‘Grand Nain’ cultivar.
The present study was intended to develop an effective micropropagation system of the economically important ‘Grand Nain’ variety of Musa acuminata Colla (AAA) having high structural fidelity and significant potential to multiply shoots under in vitro conditions using the non-conventional cytokinin 6-benzoyladenine (BOA, C12H9N5O). The young sword sucker explants were cultured on MS medium supplemented with 4.0 mg L − 1 of BOA and 2.0 mg L − 1 IAA resulted in the formation of 6.0 shoots (3.8 cm length) within 21 days. Cytokinins with NAA resulted in callus development and stalled the shoot development. Further subculturing of shoots on MS medium containing 6.0 mg L − 1 of BOA and 2.0 mg L − 1 IAA had a significant influence on overall shoot multiplication and elongation (36.2 shoots with 7.0 cm length after 3rd subculture), while 6.0 mg L − 1 of 6-benzylaminopurine (BAP, C12H11N5) and 2.0 mg L − 1 IAA produced only 20.0 shoots. The use of BOA increased the content of the photosynthetic pigments and shoots biomass. A comparative foliar micro-morpho-structural assessment revealed that the leaves derived from BOA and IAA combination had greater leaf blade thickness, well-differentiated mesophyll tissues, larger air cavities, and developed vascular tissues. Indole-3-butyric acid (IBA) was found to be more effective in root induction than α-naphthalene acetic acid (NAA) and the highest root induction (100% response, 11.0 roots with 5.5 cm length) per shootlet was detected on MS medium augmented with 2% sucrose, 50 mg L − 1 Activated charcoal and 2.0 mg L − 1 IBA. The primary hardening of plantlets was accomplished using cocopeat, and 96.5% of the plantlets survived after secondary hardening in garden soil and vermicompost mixture under ex vitro conditions. In conclusion, the use of BOA in the medium improved the quantitative and qualitative morphometric attributes of Musa acuminata cv. ‘Grand Nain’ increasing the survival rate of in vitro raised plantlets under field conditions.