Heritability and Genetic Divergence Studies in Forage Sorghum (Sorghum Bicolor L. Moench)

Abstract

Present investigation entitled “Heritability and genetic divergence studies in forage sorghum (Sorghum bicolor L. Moench)” was undertaken, involving thirty three diverse genotypes of forage sorghum under genetic divergence analysis during kharif 2019 at Crop Research Centre of SVPUA&T, Meerut to take information on variability, heritability, genetic advance, character association, path coefficient analysis and genetic divergence analysis. Data was recorded and compiled for ten traits i.e., 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 indicated that the highly significant mean differences were observed for all the ten characters under study i.e., 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 which indicates that substantial variability was present in the sorghum accessions selected for study and were suitable for further genetic and selection parameters. Genotypic and phenotypic coefficient of variation were observed high (>25%) for plant height, leaf area and green fodder yield per plant which indicating that these characters provides greater scope for improvement in forage sorghum by direct selection. High heritability coupled with high genetic advance as percent of mean recorded for plant height, leaf breadth, leaf area, stem girth, leaves per plant, leaf stem ratio, total soluble solids and green fodder yield per plant. These attributes representing high values of heritability and genetic advance as percentage of mean emerge as ideal traits for improvement through selection due to high variability and transmissibility. Green fodder yield per plant had highly significant positive association with leaf length, leaf breadth, stem girth, leaves per plant, leaf stem ratio and total soluble solids at both genotypic and phenotypic level. Hence, enhancement of green fodder yield can be achieved by improving these characters in forage sorghum. Genotypic and phenotypic path coefficient analysis of green fodder yield per plant and its component attributes showed that leaf area had the highest positive direct effect on green fodder yield per plant followed by stem girth, leaves per plant and leaf stem ratio, indicates that these traits could be considered as most important characters for improving fodder yield. Based on D2 values thirty three genotypes of sorghum were grouped into six clusters using ten component characters. Among the clusters cluster I was the largest with fifteen genotypes, cluster II and V had 4 genotypes each, cluster III with 7 genotypes, cluster IV had 1 genotype and cluster VI with 2 genotypes which concluded that in general, there was parallelism between genetic and geographic diversity. Cluster IV represented by single genotype which independently diverged from others. The formation of solitary clusters may be due to the total isolation preventing 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. Fifteen varieties grouped under Cluster I indicates their proximity and narrow genetic base. Intra cluster distance among various clusters recorded maximum intra cluster distance for cluster III (2.27), indicating that genotypes belonging to these intra clusters may be used in hybridization programme to obtain transgressive segregants with broad spectrum of genetic variability for yield and other component traits to isolate high yielding genotypes in forage sorghum. Lowest intra cluster distance was noted for cluster IV (1.01) this suggesting that these cluster genotypes have same genetic constitution i.e., homogeneous are less divergent. Average inter cluster D2 values among 33 genotypes exhibited maximum inter cluster distance values between cluster II and IV (7.75) followed by cluster IV and VI (7.29), cluster III and IV (7.04), cluster I and IV (6.73), cluster IV and V (6.71), cluster II and VI (5.91), cluster I and VI (5.76), cluster V and VI (4.89) and cluster III and VI (4.52) which, indicated that the crosses among the genotypes included in these clusters may give high heterotic response and thus better segregants to generate new material in forage sorghum. The minimum inter cluster distance was observed between clusters I and II (2.36) indicating, close association between the genotypes which is not desirable for hybridization programme. Higher cluster mean for green fodder yield per plant was observed in cluster I (568.25) followed by cluster V (564.87) and cluster II (525.12) whereas, lower cluster mean was recorded in cluster VI (362.73). For leaf area cluster mean was maximum recorded in cluster V (392.04) followed by cluster VI (376.91) and cluster III (374.39) however, minimum cluster mean value in cluster II (245.05). High cluster mean for plant height noted in cluster III (303.79) followed by cluster I (223.25) and cluster VI (220.37) while, estimated lower cluster mean in cluster IV (194.53). For days to 50% flowering cluster mean values showed maximum in cluster IV (101.67) followed by cluster VI (96.00) and cluster III (83.81) whereas, minimum cluster mean value in cluster I (79.16). Leaf length mean values were found high in cluster IV (85.07) followed by cluster III (73.80) and cluster I (72.78) and revealed lowest mean value in cluster II (62.52). Based on overall score across ten characters, the clusters were ranked and accordingly, cluster VI, cluster II, cluster IV and cluster I are the top clusters which, indicating the presence of promising accessions in them and can be extensively used for further breeding programme to generate new material. Genotypes Pratap Raj Jowar-1, Pusa Chari-23, HJ-513, Pant Chari-2, Pusa Chari-9, SSG59-3 and CSV-27 have been proved to be major contributors to its economic superiority and parents may be involved in crossing programme for developing high yielding varieties in forage sorghum. Percent contribution of green fodder yield per plant followed by leaf area, leaves per plant, plant height and leaf breadth were the major contributors towards total divergence and rest attributes contributed very little or did not contribute at all towards genetic divergence.