Purpose: To evaluate the effect of gamma irradiations on morphological and biochemical variations of in vitro shoots, regenerated plants and rhizomes of ginger (Zingiber officinale Rosc.) var. Himgiri.
Materials and methods: In vitro established shoot cultures were treated with different doses of gamma irradiations (10-100 Gy). Nonirradiated shoots were used as controls. Radio sensitivity of shoots and in vitro growth parameters were recorded. Surviving shoots along with controls were multiplied, rooted and hardened. Irradiation effect on chromosomes was evaluated by comparing with controls. Various morphological and biochemical observations were recorded in regenerated plants and rhizomes and compared to controls.
Results: Irradiated shoots showed decline in survival percentage (95% in 10 Gy to 12.33% in 100 Gy) with increase in dose rate after 4 weeks of irradiation. Shoot survival significantly decreased with irradiation dose rate above 20 Gy. Shoot multiplication rate showed an increase from 1:2 in 1st subculture to 1:9 after 5th subculture, in 10 Gy irradiated cultures with 4.5 cm average length of shoots and 8.19 number of leaves after 5th subculture. Average rooting showed an increase from 15.55% after 2nd subculture to 100% after 5th subculture, in 10 Gy irradiated shoots; however, no multiplication and rooting was observed in higher doses. In vitro rooted shoots were subjected to hardening with 100 percent survival in a mixture comprised of soil, cocopeat and FYM. One-year-old hardened plants when observed for morphological variations showed nonsignificant variations in comparison to controls. Rhizomes obtained from 10 Gy irradiated plants showed enhanced concentration of 6-gingerol and reduced crude fiber content when compared with controls.
Conclusions: Gamma irradiation doses up to 10 Gy resulted in nonsignificant phenotypic variations but can positively affect biochemical composition of rhizomes leading to development of biochemically improved mutant lines of ginger with increased 6-gingerol and lowered crude fiber content. Therefore, suggesting the lower doses of gamma irradiations for improvement of biochemical constituents in vegetatively propagated plants.
Keywords: Gamma irradiations; in vitro propagation; morphological and biochemical evaluation; Zingiber officinale.