Studies on Heterosis for Quality and Quantitative traits in Forage Sorghum (Sorghum bicolor L. Moench)

Abstract

The present investigation entitled “Studies on heterosis for quality and quantitative traits in forage sorghum (Sorghum bicolor L. Moench)” was conducted to carried out the genetic analysis of breeding material through components of variance, nature and magnitude of gene effects, genetic variability, heritability, genetic advance, correlation coefficients, general and specific combining ability effects and heterosis among yield and it components in parents and F1’s hybrids. Ten diverse parents i.e., CSV-15, Pusa Chari-6, HC-308, Pant Chari-4, G-48, HJ-513, UP Chari-4, HC-171, SSG-59-3 and ICSV-700 germplasm selected from the Department of Genetics and Plant Breeding, Sardar Vallabhbhai Patel University of Agriculture & Technology, Meerut. Ten parents diallel set excluding reciprocals made during the season of kharif 2022 by raising the crop at Crop Research Centre of S.V.P.U.A.&T., Meerut. All the forty five crosses and their ten parents grown during kharif season 2023 in randomized block design with three replications. Observations were recorded on days to 50 % flowering, plant height, leaf length, leaf breadth, stem girth, leaves per plant, leaf area, leaf stem ratio, total soluble solids, protein content, fiber content, HCN content and green fodder yield. The analysis of variance for the experiment with fifty five treatments for all the thirteen attributes viz., days to 50% flowering, plant height, leaf length, leaf breadth, stem girth, leaves per plant, leaf area, leaf stem ratio, total soluble solids, protein content, fiber content, HCN content and green fodder yield revealed significant differences among the material used in the present investigation, which indicated that wide spectrum of variation among the genotypes. The variance due to treatments was further partitioned in to their orthogonal components i.e., parents, crosses and parents vs crosses. Parents and crosses recorded highly significant differences for all the thirteen traits whereas parent’s vs crosses were found highly significant differences for all the characters except protein content and fiber content. Additive genetic variance D noted positive significant for days to 50% flowering, leaf length, stem girth, leaves per plant, leaf area, total soluble solids, protein content, fiber content, HCN content and green fodder yield, indicating predominance of additive gene action in the inheritance of these traits. Dominance components H1 and H2 recorded highly significant and positive for all the thirteen characters in F1 generation. The estimates of H1 values were higher than the values of H2 for all the attributes except leaf stem ratio, indicated that unequal allelic frequencies at relevant loci in the population. Measure of dominance effect h2 reported highly significant and positive for days to 50% flowering, plant height, leaf length, leaf breadth, stem girth, leaves per plant, leaf area, HCN content and green fodder yield, which indicated that presence of dominance in F1 generation. Value of F observed highly significant and positive for days to 50% flowering, plant height, leaf length, leaf breadth, stem girth, leaves per plant, leaf area, total soluble solids, protein content, fiber content, HCN content and green fodder yield in F1 generation, indicating the excess of dominant and positive allele in the parents for governing these attributes. Estimates for degree of dominance (H1/D)½ exhibited to be more than unity in F1 generation for all the thirteen characters viz., days to 50% flowering, plant height, leaf length, leaf breadth, stem girth, leaves per plant, leaf area, leaf stem ratio, total soluble solids, protein content, fiber content, HCN content and green fodder yield, suggested that the existence of over dominance for these attributes. Ratio of gene with positive and negative effects in the parents H2/4H1 was found less than unity theoretical value (0.25) for all the traits i.e., days to 50% flowering, plant height, leaf length, leaf breadth, stem girth, leaves per plant, leaf stem ratio, total soluble solids, protein content, fiber content and HCN content in the F1 generation, which showed that dissimilar distribution positive and negative alleles. Proportion [(4DH1)½+F/(4DH1)½-F)] indicates the ratio of dominant and recessive alleles among the parents. It was recorded more than unity for days to 50% flowering, plant height, leaf length, leaf breadth, stem girth, leaves per plant, leaf area, leaf stem ratio, total soluble solids, protein content, fiber content and HCN content, which indicated accumulation of dominant alleles in the parents for these traits. Ratio h2/H2 is an important measure of the group (s) of the genes controlling the character and exhibiting dominance. The value of this ratio was found more than unity for plant height and green fodder yield per plant in F1 generation, indicated that more than one major gene groups are responsible for governing these characters and rest of the characters observed the proportion of h2/H2 less than one unity, indicating the presence of at least one major gene or gene group is controlling these traits. Analysis of variance for combining ability showed the variance due to general combining ability highly significant for all the attributes. Specific combining ability variance was found highly significant for all the characters, indicated that the both additive and non additive gene action involved in expression of these traits. The variance components σ2g and σ2s estimated more than unity for days to 50% flowering, plant height, leaf length, leaf area, HCN content and green fodder yield, indicating the involvement of the additive gene action in all these attributes and rest trait had less than unity, which indicated that involvement of non additive gene action. The proportion of σ2g/σ2s being less than one unity for plant height, leaf length, leaf breadth, stem girth, leaves per plant, leaf area, leaf stem ratio, total soluble solids, protein content, fiber content, HCN content and green fodder yield which indicated more involvement of non additive type of gene action for these traits, whereas the ratio of σ2g/σ2s being more than unity for days to 50% flowering, which indicated that involvement of additive type of gene action for this character. The mean degree of dominance (σ2g/σ2s)1/2 observed greater than unity for plant height, leaf length, leaf breadth, stem girth, leaves per plant, leaf area, leaf stem ratio, total soluble solids, protein content, fiber content, HCN content and green fodder yield per plant, indicated the involvement of over dominance for this trait, whereas it was less than unity for days to 50% flowering, indicating that the involvement of partial dominance for this character. On the basis of overall per se performance and general combining ability effects among the lines, HC-171 and SSG-59-3 identified as good general combiners for maximum 11 attributes including green fodder yield. These parents may be handled in suitable breeding programme visa-vis selection breeding for improvement productivity of green fodder yield and per unit area in forage sorghum. On the basis of overall findings and fodder yield performance the cross combinations i.e. CSV-15 x UP Chari-4, Pusa Chari-6 x G-48, Pusa Chari-6 x UP Chari-4 and SSG-59-3 x ICSV-700 considered as best specific combiners for maximum attributes including green fodder yield for 12 to 13 other contributing characters, which may be utilized for obtaining transgressive sergeants in the next generation. On the basis of overall results and per se performance the manifestation of high degree of heterosis over better and mid parent in certain F1’s hybrids i.e., CSV-15 x G-48, Pusa Chari-6 x G-48, HC-308 x HJ-513 and Pant Chari-4 x G-48 identified that great possibility of developing hybrid for commercial cultivation. High heritability accompanied with high genetic advance as percent of mean noted for leaf breadth, stem girth, leaves per plant, leaf area, leaf stem ratio, total soluble solids and green fodder yield. This indicated that these traits were highly heritable and selection of high performing genotypes is possible to improve these attributes. Green fodder yield exhibited significant stable and positive correlation with days to 50% flowering, plant height, leaf length, leaf breadth, stem girth, leaves per plant and leaf area at genotypic and phenotypic level. These characters may be considered as important yield component in forage sorghum. Leaf breadth displayed high order of direct effect on green fodder yield per plant followed by leaves per plant, leaf length and stem girth at phenotypic and genotypic level, which indicated that the contribution of individual attributes to fodder yield is of importance in planning a sound breeding programme for developing for high yielding varieties.