Gamma radiation effect on the growth and molecular variation of Pisang Tanduk (M. Acuminata x M.Balbisiana)

Banana and plantain improvement through conventional breeding method has been slow mainly due to narrow genetic variability, sterility and polyploid nature of most banana cultivars. Thus, mutation breeding is a promising tool to create new cultivars for banana improvement. Hence, this study was conducted to investigate the effect of γ radiation on growth, morphology and genetic variation of the mutant produced. Explants were exposed to Cs-137 γ rays at doses ranging from 10-70 Gy. Sub-culturing was conducted up to M1V4, followed by induction of rooting (M1V5) before being acclimatized under nursery condition. The radiosensitivity of in vitro shoots towards radiation was assessed through the survival percentage. The highest survival rate among γ treated explants recorded was 74% in 10 Gy treatments while the lowest survivality was 20% in 70 Gy. The lethal dose (LD50) was observed in 37 Gy with 50% survival rate while irradiation of more than 37 Gy caused maximum damage to the explants. Lower doses than 37 Gy (10 and 20 Gy) dose imposed significant effect to the shoot growth. The highest average of shoot number per explant was 4.6 from the 20 Gy, followed by 3.2 shoots per explant from 10 Gy. 30 Gy treatments were found to cause significant reduction in shoot length. 10 Gy gave strong significant stimulation effect to the root length, leaf length and leaf width compared to non-treated banana seedlings. A total of 33 bands were generated from primers and combination primers with 20 bands are polymorphic. The average number of bands per primers was 2 bands and the maximum number was 11. Highest number of bands was detected in primer Nikita + 3’ LTR with also the highest polymorphic bands whereas primer LTR 6149, Sukkula LTR + LTR 6149, Sukkula LTR + 3' LTR and Sukkula LTR + 5'LTR1 yielded only monomorphic bands. The application of γ treatments had induced phenotypic and genotypic variation, thus can be usefully employed for inducing desirable mutations. Meanwhile, IRAP marker could potentially be used for the selection of desirable mutant for the development of improved banana variety.