Studies on Combining Ability, Selection Parameters and Heterosis in Forage Sorghum (Sorghum Bicolor L. Moench)

Abstract

The present investigation entitled “Studies on combining ability, selection parameters and heterosis in forage sorghum (Sorghum bicolor L. Moench)” was carried out, involving ten parents viz., Pant Chari-2, SSV-84, CSV-17, GFS-5, Pant Chari-7, CSV- 15, HJ-513, HC-136, Pant Chari-8 and SPV-462 under diallel mating design with the objectives (1) To obtain the information about the nature and magnitude of gene action, (2) To elucidate the nature of inheritance of fodder yield and other quantitative attributes, (3) To facilitate the selection of parents for hybridization programme by estimating the combining ability effect s, (4) To estimate heterosis in F1 hybrids for different quantitative characters, (5) To understand the association between fodder yield and yield contributing traits and, (6) To estimate the direct and indirect effect of different characters on fodder yield through path coefficient analysis. The experiment, consisted of 55 treatments (10 parents + 45 F1’s) was laid out in complete randomized block design (RBD) with three replications at Crop Research Center (Chirodi) of Sardar Vallabhbhai Patel University of Agriculture and Technology, Meerut, during kharif season 2017 and 2018. Data was recorded and compiled for ten characters i.e., days to 50% flowering, plant height, leaf breadth, leaf length, leaf area, stem girth, leaves per plant, leaf stem ratio, total soluble solids and green fodder yield. Data were statistically and biometrically analysed with halp of computer for obtaining various estimate of genetic paremeters. Analysis of variance for parents and crosses showed highly differed significantly for all the attributes namely, days to 50% flowering, plant height, leaf breadth, leaf length, leaf area, stem girth, leaves per plant, leaf stem ratio, total soluble solids and green fodder yield, while parent vs cross revealed highly significant for all the characters expect leaf stem ratio, which indicated that presence of great deal of diversity among the parents with respect to fodder yield and yield contributing traits. Additive genetic variance D was noted positive significant for all the characters, 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 characters in F1 generation. The estimates of H1 values were higher than the values of H2 for all the attributes, indicated that unequal allelic frequencies at relevant loci in the population. Value of F was observed highly significant and positive for plant height, leaf length, leaf area, leaves per plant, leaf stem ratio 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 ten characters viz., days to 50% flowering, plant height, leaf breadth, leaf length, leaf area, stem girth, leaves per plant, leaf stem ratio, total soluble solids 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 breadth, leaf length, leaf area, stem girth, leaves per plant, leaf stem ratio, total soluble solids and green fodder yield 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 plant height, leaf breadth, leaf length, leaf area, leaf stem ratio and green fodder yield, which indicated accumulation of dominant alleles in the parents for these traits, whereas, this ratio was less than unity for days to 50 % flowering, stem girth, leaves per plant and total soluble solids, reflecting more recessive alleles in the parents. 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, leaf breadth, leaf area, stem girth, leaves per plant and green fodder yield 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. The proportion of σ2g/σ2s being less than one unity for plant height, leaf breadth, stem girth, leaf stem ratio and total soluble solids, 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, leaf length, leaf area, leaves per plant and green fodder yield, which indicated that involvement of additive type of gene action for this character. The mean degree of dominance (σ2g/σ2s)1/2 was observed greater than unity for days to 50 %flowering, leaf length, leaf area, leaves per plant and green fodder yield, indicated the involvement of over dominance for this trait, whereas it was less than unity for plant height, leaf breadth, stem girth, leaf stem ratio and total soluble solids, which indicated that the involvement of partial dominance for these characters. On the basis of overall per se performance and general combining ability effects among the lines, SSV-84 and SPV-462 were identified as good general combiners for maximum 9 traits including green fodder yield and, Pant Chari-8 for 8 characters. 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. SSV-84 x Pant Chari-7, SSV-84 x CSV-15, SSV-84 x HJ-513, HJ-513 x HC-136, HJ-513 x Pant Chari-8, HJ-513 x SPV-462 and CSV-17 x HJ-513 were considered as best specific combiners for maximum attributes including green fodder yield for 9 to 10 other contributing characters, which may be utilized for obtaining transgressive segregants 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., Pant Chari-2 x HJ-513, Pant Chari-2 x HC-136, Pant Chari-2 x Pant Chari-8, HJ-513 x Pant Chari-8, HJ-513 x SPV-462 and HC-136 x Pant Chari-8 identified that great possibility of developing hybrid for commercial cultivation. High heritability accompanied with high genetic advance as percent of mean was noted for plant height, leaf area, stem girth, leaves per plant, leaf stem ratio, total soluble solids and green fodder yield per plant. 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 stem girth, leaves per plant and leaf stem ratio 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 leaf area, plant height and leaves per plant 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.