MATERIALS AND METHODS Determination of the optimum dose of irradiation treatment was carried out on both in vivo materials (cuttings, rhizomes, bulbs) and in vitro (tissue-cultured) materials [protocorm-like bodies (PLBs), nodes, leaf and petal cultures]. In the in vivo mutagenesis approach, cuttings, rhizomes or bulbs were irradiated at the predetermined optimum doses and then propagated vegetatively until four vegetative generations (M1V4) arereached to ensure the stability of the mutated traits. Meanwhile, the phenotypic variations were periodically observed on irradiated plants. The mutated plants were isolated and further propagated, either through conventional propagation procedures or by tissue culture (in vitro procedures).