Gamma ray irradiation combined with in vitro Polyethylene Glycol (PEG 6000) selection sought to develop and select mutants with enhance drought tolerance in shallots (Allium ascalonicum L.). The research aimed to identify an effective gamma ray dose in inducing mutation in shallot stem bases of the Bima variety and the ideal PEG concentration to select drought tolerance mutant lines. The seven doses of gamma-ray irradiation (0, 2, 4, 6, 8, 10, and 12 Gy) and four PEG concentrations (0%, 10%, 20%, and 30%) were treatments used. The results showed the LD₅₀ of gamma-ray irradiation was 5.92 Gy, while the LD₅₀ of PEG was 18.57%. The higher the dose of gamma-ray irradiation (> 8 Gy) and PEG (> 20%), the greater the inhibition in the culture’s growth. In selection media with 20% PEG, the lowest relative decrease index (RDI) was visible in surviving shoots derived from 6 Gy, which produced the longest roots. The results suggested the 6 Gy gamma-ray irradiation followed by in vitro selection using 20% PEG could be effective for developing drought-tolerant shallots. Out of 30 mutant plants, six promising lines derived from explants irradiated by 6 Gy, i.e., B6G-1, B6G-3, B6G-4, B6G-5, B6G-9, and KI-1, were able to form greater bulbs per clump and weight per bulb than the control, Bima variety.

Keywords: Shallot (A. ascalonicum L.), drought tolerance, gamma-ray irradiation, PEG 6000, in vitro selection

Key findings: Although research on drought-tolerant shallots (A. ascalonicum L.) remains scarce, this study highlights the application of mutagenesis (gamma irradiation) and in vitro selection (PEG 6000) to enhance shallot drought tolerance. Six promising mutant lines were selected for subsequent evaluation.