In vitro regeneration of Musa spp. cultivars Malbhog and Bhimkol, and assessment of genetic fidelity of regenerated plantlets using molecular markers
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Date
2019-07
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AAU, Jorhat
Abstract
Banana (Musa spp.), belonging to the plant family Musaceae, is one of the major fruit crops of the world. Banana cultivars Bhimkol (Musa balbisiana, BB) and Malbhog (Musa paradisiaca, AAB) are popularly grown in the North-Eastern parts of India. Both cultivars are popular and important from the evolutionary and commercial point of view and, particularly Bhimkol banana is associated with improved vigor and tolerance to biotic and abiotic stresses. Malbhog is highly valued and the most desired for its excellent fruit qualities particularly marvelous taste, appealing aroma and a greater number of fruits per hand and higher post-harvest life. Since ancient times, people have been consuming banana fruit as dessert, dietary supplement, and for nutrition as it is rich in carbohydrates, vitamins and proteins. However, conventional banana propagation is time-consuming and gives lower yields due to various constraints such as biotic/abiotic stresses and lack of availability of healthy suckers. Moreover, the production by conventional means is not able to meet the demands of the growing market. So, the use of tissue culture technique and development of in vitro regeneration protocol for popular cultivars such as Malbhog and Bhimkol will not only lead to mass multiplication with better yields but also help in conservation of local genotypes.
In the present investigation, an attempt has been made to optimize an efficient in vitro shoot regeneration system for Bhimkol and Malbhog. The study was initiated by standardizing shoot regeneration protocol, using banana shoot tips as explants in modified MS medium by using different concentrations of BAP (6-Benzylaminopurine) (2, 3, 4, 5, 6, 7, 8, 9 and 10 mg/l). In Bhimkol, although shoot regeneration was observed in 7 mg/l BAP, but the regeneration was much slower and no multiple shoot formation was seen. Since, it is a slow growing genotype and also the level of phenolic compounds is very high, regeneration was not found to be satisfactory even on treating the explant with ascorbic acid. Hence, for Bhimkol the in vitro regeneration protocol needs further standardization. In Malbhog, MS medium supplemented with various combinations of BAP and NAA (1-Naphthaleneacetic acid) were used for the optimization of multiple shoot regeneration. The results indicate that shoot regeneration and proliferation was significantly higher in the presence of 10 mg/l BAP and 0.2 mg/l NAA as compared to other concentrations in terms of the number of days required for shoot initiation, number of shoots developed per explant and length of shoots. For assessment of genetic fidelity of the multiple shoots, DNA was isolated from leaves of in vitro regenerated shoots and the field grown mother plant. Thirteen SSR primer pairs (already reported) were used in the analysis which resulted in banding patterns that were uniform and monomorphic for all the clones tested and comparable to the mother plant from which the cultures had been established. This indicated that all the regenerated shoots are true to type with no variation in their genetic makeup. Thus, the optimized shoot regeneration protocol could be potentially used for mass multiplication of Malbhog, once the in vitro rooting and hardening of regenerated plantlets is standardized.