Received: 10 Jun 2021 Accepted: 10 Aug 2021 Revised: 05 Aug 2021 https://doi.org/10.37992/2021.1203.096 Vol 12(3):685 - 692 685 Electronic Journal of Plant Breeding Research Article Ascertaining gamma ray dosage sensitivity of in vitro cultures in banana cv. Ney Poovan (Musa AB) C.Y. Shalini Udaya 1 , K. Soorianathasundaram 2 *, M. Ganga 3 , P. Paramaguru 4 , and U. Sivakumar 5 1 Department of Fruit Science, Horticultural College & Research Institute, TNAU, Coimbatore, Tamil Nadu, India. 2 Controllerate of Examinations, TNAU, Coimbatore, Tamil Nadu, India. 3 Department of Floriculture and Landscaping, Horticultural College & Research Institute, TNAU, Coimbatore, Tamil Nadu, India 4 Horticultural College and Research Institute for Women, Tiruchirapalli, Tamil Nadu, India 5 Department of Agricultural Microbiology, TNAU, Coimbatore, Tamil Nadu, India *E-Mail: sooria@tnau.ac.in Abstract In a vegetatively propagated and parthenocarpic crop like banana, the mutation breeding method ofers considerable scope to create genetic variability for crop improvement. It is necessary to determine the LD 50 dose for optimizing the radiation dosages when gamma rays are used for mutation induction. In the present study, in order to fx the LD 50 dose for explants cultured in vitro in cv. Ney Poovan, in vitro shoot tips were subjected to fve diferent doses of gamma rays ranged from 5 to 25 Gy. Proliferating multiple shoots were subjected to fve diferent doses of gamma rays ranged from 2 to 10 Gy. The results revealed a linear and signifcant reduction in the survival percentage, shoot length and number of shoots with increasing levels of gamma irradiation doses in both the category of explants. The probit curve based analysis on mortality of treated explants revealed that LD 50 dose of gamma rays to be 18.77 Gy for cultured shoot tips and 6.97 Gy for proliferating multiple shoots under in vitro. Key words: Gamma irradiation-Shoot tip cultures-Lethal dosage-Banana. INTRODUCTION Banana (Musaspp., Musaceae) is considered not only as a fruit crop but also as the fourth most economically important food crop after wheat, rice and maize in terms of production and quantity of consumption, Bananas are seriously afected by many fungal, bacterial, viral and nematode pathogens and as well serious pests like stem weevil and corm weevil. Genetic improvement of bananas through conventional breeding for yield improvement or for pest and disease resistance is difcult due to several reasons such as inherent polyploidy nature, heterozygosity, interspecifc hybridity, parthenocarpic fruit development and low levels of male and female fertility. Mutation breeding is often resorted to creating genetic variability to screen and select useful variants in bananas (Novak et al., 1993; Pillay and Tripathi, 2007). Determination of lethal dose of the mutagen is a prerequisite to optimizing the doses for recovery of a large number of population in mutation breeding (Leitao, 2012). Among the diferent mutagenic agents, gamma rays are frequently employed for mutation induction in bananas. Earlier some induced mutation attempts have also resulted in improved varieties. Novak et al. (1990) used gamma radiation to induce an early fowering mutant of Grand Naine called GN-60Gy. In Malaysia, a further