Effects of acute gamma irradiation on the morphology of Curcuma alismatifolia ‘Siam Shadow’ and C. alismatifolia ‘Siam Scarlet’

Curcuma alismatifolia (Pathumma in Thailand), also known as Siam Tulip, is an economically valuable cut flower in Thailand and is continuously bred to enhance its captivating array of colors. This study aimed to investigate the effects of acute gamma irradiation on 2 cultivars of C. alismatifolia ‘Siam Shadow’ and C. alismatifolia ‘Siam Scarlet’ for in vitro propagation and determination of the lethal dose 50 (LD50). The irradiation was conducted at doses of 0, 20, 30, 40 and 80 Gy using young shoots tissue culture. The results of the experiment revealed that the LD50 for ‘Siam Shadow’ could not be determined while ‘Siam Scarlet’ was 29.06 Gy. ‘Siam Shadow’ exhibited chimera leaf formation when exposed to a gamma irradiated dose of 40 Gy, while ‘Siam Scarlet’ exhibited chimera leaf formation when gamma irradiated at doses of 20 Gy in vitro. After planting in a greenhouse, ‘Siam Shadow’ was irradiated with 30 Gy of gamma irradiated, had reduced bract numbers and the bracts became smaller. Conversely, ‘Siam Scarlet’ irradiated with 20 Gy of gamma irradiated, produced smaller inflorescences with only 2 bracts, while irradiation with 30 Gy resulted in 2 lobes and spotted leaves at the edges of the leaves. The results indicated that both the C. alismatifolia cultivars and gamma irradiation rates had a significant influence on survival rate, number of shoots, plant height, chlorophyll mutants and morphology. As the outcome, it was determined that gamma irradiation with optimum doses of gamma rays could induce new characteristics in C. alismatifolia.