Gamma radiation induced phenotypic diversity in Dendrobium ‘Emma White’

Abstract

Dendrobium, one of the largest genera of family Orchidaceae, is economically important both as an ornamental and medicinal crop. Varietal improvements of Dendrobium through the conventional breeding methods are difficult and challenging due to existence of incompatibility among the respective primary gene pool. Gamma irradiation technique is used to induce variability and generate mutants with improved traits in a short period. In our study, protocorm-like-bodies (PLBs) of Dendrobium hybrid ‘Emma White’ were exposed to gamma rays (of 10 - 80 Gy) and in vitro propagated up to M1V5 generation. Plantlets were regenerated from PLBs treated at 10, 20 and 40 Gy; while 60 and 80 Gy treated PLBs showed only proliferation even after 24 months of post-irradiation treatment. Phenotypic variations were recorded among the plantlets during the ex-vitro hardening stage. Leaf variations in terms of shape, size, structure, surface, tip and colour were observed in plantlets generated at 10 Gy. Significant variations and deformity were observed in leaf structure and arrangement at 40 Gy radiation level. Among 120 putative mutants, 12 lines viz. 10/4, 10/5, 10/12, 10/17, 10/35, 10/36, 10/60, 10/66, 10/75, 10/76, 10/82, 10/85 were selected for further analyses including molecular characterization. Mutant line 10/46 was identified with early flowering, within 09 months 24 days from the date of hardening. Findings indicate impact of gamma radiation effects on enhancing genetic variability of both vegetative and flowering traits of Dendrobium hybrid.