Induction of variability through mutagenesis in neelayamari (Indigofera tinctoria L.)

Abstract

The study entitled “Induction of variability through mutagenesis in neelayamari (Indigofera tinctoria L.)” was carried out in the Department of Plant Breeding and Genetics, College of Agriculture, Vellayani during the period 2006-2008, with the objective of inducing variability for higher biomass yield and indigotin content in leaves. Indigofera tinctoria is a valuable medicinal plant, which is also utilized as a natural source of the blue dye, ‘indigo’. At present the leaf biomass obtained from the genotypes currently cultivated is not appreciable. Hence an attempt has to be made to evolve variants with higher leaf yield and indigotin content. Mutation breeding has been attempted in this study with a local variety. The LD50 was calculated as 20.0 KR gamma rays. The mean performance for all the characters was reduced as the doses of mutagen increased in M1 generation. In M2 generation the positive shift in mean plant height, plant spread, girth of stem, number of branches, number of leaves, weight of leaves, weight of shoots, weight of pods and indigotin content were observed in the intermediate dose of mutagen. Indigotin content of leaves increased significantly with increased doses of gamma rays treatments when compared to control. The optimum dose for maximum yield and yield contributing characters ranged between 17.5 KR and 22.5 KR of gamma rays mutagen. A high magnitude of phenotypic coefficient of variation and genotypic coefficient of variation were noticed for the characters viz., harvest index, leaf area index, dry weight of pods and number of branches. High estimates of heritability were observed for all the characters studied, the highest being exhibited by fresh weight of leaves. Maximum genetic advance was observed for the character harvest index while fresh weight of shoots expressed the minimum. Correlation coefficient between shoot yield and its components indicated significant positive association of yield with plant height, leaf area index, fresh weight of leaves, number of leaves, dry weight of leaves, dry weight of shoots, fresh weight of pods and dry weight of pods, where as harvest index showed significant negative correlation. Path coefficient analysis of important yield attributes indicated that the number of branches, plant height and indigotin content had the maximum direct effect on fresh weight of shoot and minimum for dry weight of leaves. Indigotin content has negative correlation with yield where as it has direct effect on yield through other correlated characters. This indicates that selection for improvement for indigotin content should be carried out with other characters also. It also indicates that there should be an optimum level of biomass yield for higher indigotin content. Frequent harvest will influence the indigotin content favourably. This has to be determined by assessing the regression coefficient for other characters with indigotin content. The selection index score was highest for control followed by the treatment 22.5 KR and 20.0 KR of gamma rays. Selected mutants showed morphological variation over the control. High yielding mutants were observed in plants treated with 20.0 KR of gamma ray. A total of five high yielding mutants were identified and their yield characters and indigotin were also found out for further evaluation. Raising M3 progeny lines from each of these plants and evaluation of the lines in comparison with the control plants are suggested as future line of work.