The present research was focused in the development of photosynthetically efficient (PhE) and non-lodging mutants by utilizing ethyl methane sulphonate (EMS) and gamma radiation in the kodomillet variety CO 3, prone to lodging. Striking variations in a number of anatomical characteristics of leaf anatomy for PhE and culm thickness for lodging resistance was recorded in M2 (second mutant) generation. The identified mutants were subjected to transcriptomic studies to understand their molecular basis. Expression profiling was undertaken for pyruvate phosphate dikinase (PPDK), Nicotinamide Adenine Dinucleotide Phosphate Hydrogen—(NADPH) and NADP-dependent malate dehydrogenase (NADP-MDH) in the mutants CO 3-100-7-12 (photosynthetically efficient) and in CO 3-200-13-4 (less efficient). For lodging trait, two mutants CO 3-100-18-22 (lodged) and CO 3-300-7-4 (non-lodged) were selected for expression profiling using genes GA2ox6 and Rht-B. The studies confirmed the expression of PPDK increased 30-fold, NADP-ME2 ~1-fold and NADP-MDH10 was also highly expressed in the mutant CO 3-100-7-12. These expression profiles suggest that kodomillet uses an NADP-malic enzyme subtype C4 photosynthetic system. The expression of Rht-B was significantly up regulated in CO 3-300-7-4. The study highlights the differential expression patterns of the same gene in different lines at different time points of stress as well as non-stress conditions. This infers that the mutation has some effect on their expression; otherwise the expression levels will be unaltered. Enhancement in grain yield could be best achieved by developing a phenotype with high PhE and culm with thick sclerenchyma cells.
Mutation breeding is the defined approach used for crop production and has played a key role in the creation of several varieties. The present research was carried out to induce mutants in kodo millet variety CO 3 using a physical mutagen (gamma rays) and a chemical mutagen (Ethyl Methane Sulphonate) for creating novelty. Seeds were treated with five doses of gamma-rays viz., 100 Gy, 200 Gy, 300 Gy, 400 Gy, and 500 Gy at BARC, Kalpakam and with three concentrations of EMS viz., 24.15 mM, 32.20 mM and 40.25 mM. In the laboratory test, root and shoot lengths of seedlings were decreased with an increase in the dose of gamma rays and EMS. In field study, the germination percentage and survival rate of seedlings were decreased with an increase in the dose of gamma irradiation and EMS. In M2 generation, five types of chlorophyll mutations viz., albino, xantha, striata, chlorina and albomaculata were observed. Xantha and chlorina were observed in all treatments, whereas, striata and albomaculata were observed only in 200 Gy. Based on the biological damages on M2 plants, mutagenic effectiveness and efficiency were estimated. Both mutagenic effectiveness and efficiency reduced with the increase in the dose of irradiation. Regarding height reduction and lethality, the dose of 100 Gy in gamma treatment and 32.20 mM concentration in EMS treatment recorded maximum efficiency. The mutagenic effectiveness was found to be higher at gamma rays irradiated with 100 Gy and in EMS, in 24.15 mM concentration. The 100 Gray dose and 24.15 mM concentration was found to be highly effective for inducing mutation in kodo millet.
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