Combining Ability and Heterosis Analysis in Relation to Yield and Yield Components in Forage Sorghum (Sorghum Bicolor L. Moench)

Abstract

The present investigation entitled “Combining ability and heterosis analysis in relation to yield and yield components in forage sorghum (Sorghum bicolor L. Moench) was 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., UP Chari-1, HC-308, UP Chari-2, HC-171, Pant Chari-8, CSV-17, Pant Chari-6, CSV-84, Pant Chari-5 and Rajasthan Chari-1, germplasm selected from SVPUA&T, Meerut, U.P. Ten parents diallel set excluding reciprocals was made during the season of kharif 2018 by raising the crop at Crop Research Centre of Sardar Vallabhbhai Patel University of Agriculture & Technology, Meerut. All the 45 crosses and their ten parents were grown during kharif season 2019. All the 45 F1’s hybrids along with ten parents were sown in randomized block design with three replications. Observations were recorded on days to 50% flowering, plant height, leaf breadth, leaf length, stem girth, leaves per plant, leaf area, leaf stem ratio, total soluble solids and green fodder yield. Analysis of variance for parents and crosses showed highly differed significantly for all the characters i.e., days to 50% flowering, plant height, leaf breadth, leaf length, stem girth, leaves per plant, leaf area, leaf stem ratio, total soluble solids and green fodder yield. Parents vs crosses exhibited highly significant for the attributes namely, days to 50% flowering, plant height, leaf breadth, leaf length, leaf area and green fodder yield, which indicated that wide genotypic differences among the parental lines and F1’s hybrids. High heritability coupled with high genetic advance as percent of mean was observed for the traits viz., plant height, and leaves per plant, leaf area, stem girth, leaf stem ratio and green fodder yield, suggesting that the genes governing these characters may have additive effect. Green fodder yield exhibited significant stable and positive correlation with days to 50% flowering, plant height, leaves per plant and stem girth at both genotypic and phenotypic levels, suggested that selection of these characters may be practiced for higher fodder yield in forage sorghum. Leaf area displayed high order of direct effect on green fodder yield per plant followed by plant height, leaves per plant and stem girth at both phenotypic and genotypic levels, indicated that these attributes may contribute for enhanced fodder yield in forage sorghum. Estimates of additive genetic variance D was noted positive significant for all the characters except leaf stem ratio, indicated predominance of additive gene action in the inheritance of these attributes. Dominance components H1 and H2 recorded highly significant and positive for all the traits except leaf stem ratio in F1 generation. The estimates of H1 values were found higher than the values of H2 for all the ten attributes, indicated that unequal allelic frequencies at relevant loci in the population. Value of F was observed highly significant and positive for characters viz., days to 50% flowering, plant height, leaves per plant, leaf length, leaf area and green fodder yield in F1 generation, which indicating the excess of dominant and positive allele in the parents for controlling these attributes. Estimates for degree of dominance (H1/D)½ exhibited to be more than unity in F1 generation for the traits i.e., plant height, leaves per plant, leaf breadth, leaf length and total soluble solids, suggested that the existence of over dominance for these characters. Ratio of gene with positive and negative effects in the parents H2/4H1 was found less than unity theoretical value (0.25) for days to 50% flowering, plant height, leaf breadth, leaf length, leaf area, leaf stem ratio and total soluble solids in the F1 generation, which indicated 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, leaves per plant, leaf breadth, leaf length, leaf area, stem girth and total soluble solids, which indicated accumulation of dominant alleles in the parents for these traits, whereas, this ratio was less than unity for leaf stem ratio and green fodder yield, reflecting more recessive alleles in the parents. Ratio h2/H2 is an important measure of the group (s) of the genes governing the character and exhibiting dominance. The value of this ratio was found more than unity for leaves per plant, stem girth and green fodder yield in F1 generation, indicated that more than one major gene groups are responsible for controlling these attributes 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. The mean degree of dominance (σ2g/σ2s)1/2 was estimated greater than unity for days to 50% flowering, leaf area, stem girth, leaf stem ratio and green fodder yield, indicated the involvement of over dominance for these characters, whereas it was less than unity for plant height, leaves per plant, leaf breadth, leaf length and total soluble solids, indicating that the involvement of partial dominance for these attributes. On the basis of overall gca effects and per se performance among the lines, UP Chari-1 and Pant Chari-5 were identified as good general combiners for maximum 7 traits including green fodder yield, HC-171 for 6 characters and HC-308 for 5 attributes., suggested that these parents may be used in the hybridization programme aimed devolvement of superior genotypes/varieties in forage sorghum. On the basis of overall results and fodder yield performance the F1’s hybrids viz., UP Chari-1 x HC-308, UP Chari-1 x Rajasthan Chari-1, HC-308 x UP Chari-2, HC-308 x HC-171, HC-308 x CSV-17, HC-171 x CSV-84 and Pant Chari-5 x Rajasthan Chari-1 were identified as best specific combiners for maximum attributes including green fodder yield for 9 to 10 other contributing traits, which may be utilized for obtaining transgressive segregates in the next generation. On the basis of overall findings and per se performance the manifestation of high degree of heterosis over better and mid parent in certain cross combinations i.e., UP Chari-1 x HC-308, UP Chari-2 x CSV-17, UP Chari-2 x Pant Chari-5, CSV-84 x Rajasthan Chari-1 and Pant Chari-5 x Rajasthan Chari-1, suggested that great possibility to produce higher fodder yield varieties/genotypes.