Determination of molecular diversity in parents and heterosis, combining ability and stability of derived test crosses in maize (Zea mays L.)
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Date
2015-12
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G.B. Pant University of Agriculture and Technology, Pantnagar - 263145 (Uttarakhand)
Abstract
The present investigation includes generation of 80 single cross hybrids by combining 20 lines and 4 testers followed by evaluation of hybrids along with parents and check cultivars in four environments namely, rainfed 75cm X 20cm spacing, rainfed 75cm x 25cm spacing, low temperature 75cm X 20cm spacing and water logging 75cm X 20cm spacing to determine heterosis, combining ability and stability over the environments. In addition, sequence related amplified polymorphism (SRAP) markers were also used to determine molecular diversity among the parents. Pooled analysis of variance over environments for combining ability indicated that variance due to lines, testers, line x tester interaction component, line x environment interaction and higher order interaction were significant for all characters. Estimates on nature and magnitude of heterosis indicates that promising crosses for yield and yield component traits were H56 for cob length, H14 and H44 for ear diameter, H59 and H10 for number of kernel rows, H16 and H24 for number of kernel per row, H27, H60 and H77 for 100-kernel weight and H68 and H79 for grain yield. Based on combining ability analysis, the crosses identified to be promising for grain yield were H68 (8.37), H71 (8.28), H10 (7.54), H29 (6.48), H14 (6.14), H74 (5.42), H79 (5.30), H3 (5.29), H21 (4.90) and H54 (4.89). AMMI analysis showed that the hybrids H43 and H60, H69 and H79, H30 and H75 were promising in terms of stability and higher per se performance for number of kernel rows, number of kernel per row and hundred kernel weights, respectively. Based on the IPCA1 and IPCA2 scores, and per se performance, hybrids H44 and H35 were identified to be stable as well as most productive. Molecular diversity of parental lines for all thirty markers was found polymorphic. The number of band position generated by these thirty markers for all the twenty four genotypes were 184, which gave an average of 6.13 alleles per marker. Two rare alleles, one of 350 bp with primer M1E3 in L9 and second of 600bp with primer M4E3 in L9 were identified, which can be used for identification and characterization of the genotype. The dendrogram constructed from SRAP marker data divided twenty four maize inbred lines into five clusters: Cluster I, II, III, IV and V. To categorize the genotype into different clusters, mean genetic similarity coefficient (0.85) was considered arbitrarily as a guide line, and genotypes classified in to different clusters based on inter-cluster distance of 0.85 or less. The correlation analysis of grain yield with SCA and heterosis indicated significantly positively correlation with mid parent heterosis, better parent heterosis, commercial heterosis and SCA. Correlation between genetic distance and yield was found highly significant i.e. r=0.382* which clearly supports the idea that SRAP based GD is useful in assessment of the difference between the parents which can be exploited through heterosis. The investigation, therefore, has been successful in determining heterosis, combining ability and stability of parents and crosses, and molecular diversity of the parental lines. On overall basis, the hybrids H68 and H79 were found superior in all environments for heterosis and SCA while H44 and H35 were found most stable across the environments. These hybrids may be tested in multi-location trials for determining their worth as hybrid cultivars.
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Thesis-PhD
Keywords
determination, molecular genetics, genetic diversity, hybridization, heterosis, combining ability, stability, crosses, maize, Zea mays