Genetic Variability, Heritability and D2 Analyses in Forage Sorghum (Sorghum Bicolor L. Moench)

Abstract

Present investigation entitled “Genetic variability, heritability and D2 analyses in forage sorghum (Sorghum bicolor L. Moench)” was undertaken, involving forty diverse genotypes of forage sorghum under genetic divergence analysis during kharif 2018 at Crop Research Centre of Sardar Vallabhbhai Patel University of Agriculture and Technology, Meerut to take information on variability, heritability, genetic advance, character association among the characters, path coefficient analysis and genetic divergence analysis, so as to identify the traits of interest and to select divergent parents for their use in further breeding programme to evolve suitable genotypes in forage sorghum. Data was recorded and compiled for ten attributes namely, days to 50% flowering, plant height, leaf length, leaf breadth, leaf area, stem girth, leaves per plant, leaf stem ratio, total soluble solids and green fodder yield per plant. Data were statistically and biometrically analyzed with help of computer for obtaining various estimates of genetic parameters. Analysis of variance exhibited significant differences among the material used in the present investigation for all the attributes viz., days to 50% flowering, plant height, leaf length, leaf breadth, leaf area, stem girth, leaves per plant, leaf stem ratio, total soluble solids and green fodder yield per plant, indicated that the presence of genetic variability in the material under study. Out of the 6 clusters, cluster I with 3 genotypes, cluster II had 10 genotypes, cluster III with 5 genotypes, cluster IV had 7 genotypes, cluster V with 6 genotypes and cluster VI had 9 genotype based on present investigation, it was concluded that in general, there was parallelism between genetic and geographic diversity. The cluster I and cluster III represented by three or five genotypes which independently diverged from others. The formation of solitary clusters may be due to the gene flow or intensive natural/human selection for diverse adaptive complexes. These genotypes may be very unique and useful in breeding point of view. Ten genotypes grouped under Cluster II, indicating their proximity and narrow genetic base. The intra cluster distance among various clusters recorded maximum intra cluster distance for cluster III (2.63) and lowest intra cluster distance was noted for cluster IV (2.09). The maximum intra cluster distance was because of wide genetic diversity among its genotypes. The chance of developing good segregates by crossing the genotypes of the same cluster showing low value for intra cluster distance are very low. Therefore, it would be logical to attempt crosses between the genotypes of clusters separated by larger inter cluster distances. The little diversity and selection of parents within the cluster having higher mean for a particular character may also be useful for further developing high yielding forage sorghum varieties. Average inter cluster D2 values among 40 genotypes exhibited maximum inter cluster distance values between cluster I and III (4.51) followed by cluster I and IV (4.38), cluster I and II (3.92), cluster I and VI (3.88), cluster III and VI (3.86) and cluster III and V (3.59). The clearly indicates that the genotypes included in this clusters are having broad spectrum of genetic diversity and could very well be used in hybridization programme of forage sorghum for improving fodder yield. The minimum inter cluster distance was observed between clusters II and IV (2.47) which indicates that the genotype of these clusters had close relationship and hence, may not be emphasized upon to be used in hybridization programme. The comparison of cluster means for ten traits under study attributes considerable genetic differences between the clusters regarding one or more characters. Clusters I exhibited maximum values of cluster mean for days to 50% flowering, stem girth, leaf stem ratio and total soluble solids. Cluster. Cluster III estimated maximum values of cluster mean for plant height and leaves per plant. Cluster IV recorded high mean values for stem girth. Cluster V observed maximum values of cluster mean for leaf length, leaf area and green fodder yield per plant. These findings indicated that the genotypes having high mean values for respective traits gathered in the clusters showing high cluster mean for respective trait. Individually, the genotypes from the respective clusters would be exploited according to the objective of the breeding programme. Therefore, the elite genotypes GFS-4, GFS-5, Jawahar Chari-6, Jawahar Chari-69 and SPV-15 may be involved in crossing for developing fodder yield. Crosses suggesting parents belonging to most divergent clusters would be expected to manifest maximum heterosis and also wide variability of genetic architecture. Thus the crosses between the genetically diverse genotypes of cluster III characterized by plant height and leaves per plant with genotype GFS-4, GFS-5, Jawahar Chari-6, Jawahar Chari-69 and SPV-15 Cluster III with genotype SPV-669, SPV-815 and SSG-59-3 Cluster I characterized by days to 50% flowering, leaf stem ratio and total soluble solids are expected to show high heterosis and are also likely to produce new recombinants with desired characters and may be rewarding and effective in forage sorghum improvement programme. Hence, the above identified eight genotypes as potential parents can be utilized in further breeding programme in which the as above attributes will be considered for selection to achieve the best result of the breeding programme. Percent contribution of leaf area followed by green fodder yield per plant, stem girth, leaf breadth, days to 50% flowering and leaf stem ratio contr ibuted most towards genetic divergence. Remaining traits contributed very little or did not contribute at all towards genetic divergence. Green fodder yield per plant showed positive and significant correlation with plant height and leaves per plant at both genotypic and phenotypic level, indicated that these characters may be considered as important yield components in forage sorghum. Leaf area displayed high order of direct effect on green fodder yield per plant followed by leaf length, leaves per plant and leaf breadth towards green fodder yield per plant at both genotypic and phenotypic level, suggested that these traits plays a major role for improvement of yield potential of fodder sorghum. Genotypic coefficient of variation (GCV) and phenotypic coefficient of variation (PCV) were high (>25%) for leaf stem ratio, total soluble solids and green fodder yield per plant, suggested that there was a possibility of improvement of fodder yield through direct selection. High heritability coupled with high genetic advance showed for plant height, leaf length, leaf breadth, leaf area, leaf stem ratio, total soluble solids and green fodder yield per plant, indicating that these traits are governed through additive gene action and phenotypic selection for these attributes will be effective.