Mohanakumaran, NJayachandran, B KKAU2019-02-212019-02-211989170275http://krishikosh.egranth.ac.in/handle/1/5810096288PhDInvestigations in ginger cv. Rio-de-Janeiro, were carried out during 1985-89 for studying the effect of gamma rays and ethyl methane sulphonate (EMS) on the growth, yield and flowering in the VM1 generation, for assessing the variability including tolerance/resistance to bacterial wilt and soft diseases in the VM2 and for studying the VM3 progenies of the desirable VM2 plants. Dose standardization studies using 10 doses of gamma rays (from 0.5 to 5.0 krad) and 11 doses of EMS (from 8 to 150 mM) revealed that the LD50 for sprouting and survival was between 0.5 and 1.0 krad gamma rays and below 8 mM EMS. For the VM1 study, five doses each of gamma rays (0.5 to 1.5 krad) and EMS (2 to 10 mM) were used. Delayed sprouting occurred to a limited extent. Sprouting, survival, plant height, number of tillers and leaves, and rhizome yield decreased as the doses of the mutagens increased. In general, there was a tendency for recovery of growth parameters as the growth phase advanced. The number of plants with chlorophyll chimera was more in the radiation treatments. Flower production was not sufficient to draw valid conclusions. In the VM2 generation, plant height exhibited a negative shift. Tiller, leaf and rhizome production, at the lower doses of the mutagens in general, exhibited positive shifts and at the higher doses, negative shifts. Wide range of variability was observed with respect to these characters. Pollen fertility was not seen influenced by the treatments. Screening the VM2 plants against bacterial wilt and soft rot diseases did not enable the isolation of tolerant/resistant material. Study of the mutant in the VM3 revealed that majority of the plants failed to express all or some of the characters. A few plants with more yield and dryage, and more volatile oil and NVEE content, were located. The studies indicated that though the range of variability induced is high, recovery of the mutants is very low; probably due to the multicellular nature of the apices of the rhizomes treated, and the consequent chimera formation and diplontic selection. Follow up of the mutation generation up to VM4 or VM5 or till stability is achieved and avoiding storage of the rhizomes between the generations have been considered necessary. Repeated, intensive and large scale induction and continuous screening for disease resistance is worth attempting. Using in vivo and in vitro adventitious bud techniques, somaclonal variation, in vitro screening for disease resistance, induction of mutation immediately after the harvest when buds are in ontogenetically young stage of development, and raising of VM2 and subsequent generations without storage of seed rhizome irrespective of the season, are areas suggested for future research.ennullThesis