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Subject: Genetics and Plant Breeding × End date: 2016 × Thesis Type: Ph.D ×
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    ThesisItemOpen Access
    STUDIES ON COMBINING ABILITY AND GENETIC DIVERSITY OF PARENTAL LINES FOR EXPLOITATION OF HETEROSIS IN RICE (ORYZA SATIVA L
    (2014) Borah, Pulin
    The present investigation was conducted at Assam Agricultural University, Jorhat with three broad objectives - (i) to identify potential maintainer and restorer lines from local and improved germplasm, (ii) to study the genetic diversity of CMS, maintainer and restorer lines and (iii) to assess combining ability of CMS and restorer lines. Out of 79 lines evaluated, 22 restorers identified were for 1A, 13 for 3A, 3 for 4A and 10 for 5A based on pollen and spikelet fertility, whereas 3, 2 and 1 maintainers were obtained for IR68888A, IR79156A and IR80555A respectively. Morpho-physiological characterization of the genotypes revealed 6 characters as monomorphic, 12 as dimorphic and 32 as polymorphic. PCV and GCV were high for chaffs per panicle, grains per panicle, grain yield per plant, flag leaf area, culm length, days to first and 50% flowering. Narrow difference between PCV and GCV estimates suggested effective selection for these traits. High heritability coupled with high genetic advance was recorded for days to first flowering, days to 50% flowering, days to maturity, culm length, grains per panicle, flag leaf length, flag leaf breadth and flag leaf area. D² statistics grouped the genotypes into 9 clusters with the highest inter-cluster distance between clusters II-III and IV-IX. The most important characters contributing towards divergence were days to first flowering (40.91%) followed by culm length (17.88%), grains per panicle (9.9%) and panicle length (7.88%). At molecular level, 76 alleles were detected using 15 SSR markers with an average of 5.07 per marker. The Jaccard’s coefficient of similarity ranged from 0.758 to 0.111with an average of 0.385 suggesting diverse nature of the genotypes. The Mantel matrix correspondence test indicated that clusters produced based on morphological and SSR markers were not conserved. The line x tester analysis revealed preponderance of non-additive gene effects suggesting heterosis breeding as a suitable approach for yield improvement. Among the lines, 4A was the best general combiner for earliness, dwarfness and effective tillers per plant and 1A for grains per panicle. A good number of cross combinations had significant SCA effects in desirable directions. The degree of mid/better parent and standard heterosis varied with crosses and characters. Two for panicle length, 16 for effective tillers, one for grains per panicle, 44 for 1000-grain weight and one for biological yield exhibited significant heterobeltiosis as well as standard heterosis. The most productive 14 hybrids recorded 10.12% to 56.46% standard heterosis over Ranjit and could be chosen for evaluation in preliminary yield trials.