Effect of Heat Stress on Tissue Culture Response in Wheat Genotypes

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The effect of heat stress on tissue culture responses like callogenesis and organogenesis including green structures formation and rhizogenesis was studied in four wheat genotypes Sonara-64, PBW-343, HD-2967 and SIDS. Media were identified for callus formation and organogenesis from cultured mature embryos, the best medium for callus formation was MS + 4mg/l 2,4-D and for organogenesis MS + 1mg/l BAP + 0.5gm/l NAA. Mature embryos from pre-heat treated seeds were induced to develop callus and on the basis of calculated heat susceptibility index (HSI) and heat tolerance index (HTI), the genotype HD-2967 was the most heat tolerant followed by PBW-343. Genotype SIDS was the most heat sensitive followed by Sonara-64. The formed calli under controlled and heat stress were further pre-heat treated and cultured on differentiating medium for organogenesis. Genotype HD-2967 showed the best response followed by PBW-343, Sonara-64 and SIDS respectively under heat stress indicating their relative heat tolerance. Thus based on tissue culture responses under heat stress genotype HD-2967 and PBW-343 were heat tolerant and Sonara-64 and SIDS were heat sensitive. Molecular characterization study of eleven genotypes resulted in successful amplification with 12 SSR primer pairs. A total of 79 allelic variants were detected with an average of 6.07 alleles per locus and total 46 unique alleles were observed with an average of 3.53 unique alleles per locusat 13 SSR loci. The highest number Name of Student : Anant Raj Admission No./Registration No. : M/AB/199/2017-18 MajorAdvisor : Dr. Harsh Kumar Degree to be awarded : M.Sc.(Ag) in Agricultural Biotechnology Major Subject : Agricultural Biotechnology Minor Subject : Plant Breeding & Genetics Year : 2019 Total pages of the Thesis : 70+i-xiv (Bibliography) Title of the research problem : “Effect of heat stress on tissue culture response in wheat genotypes” of alleles per locus was observed in the B genome (38 alleles) as compared to A (24) and D (17) genomes. Polymorphism information content (PIC) value ranged from 0.327 for the primer pairXgwm160 to 0.878 for the primer pairXgwm 577with an average of 0.764. The similarity coefficient was the maximum between HD-2967 and BWL-9022 (0.519) and the minimum (0.0) infour pair-wise combinations HD-2967 with Purulla, PBW-343 with Sonalika, BWL-9022 with Sonalika and KSG-1186 with Sonalika. It ranged from 0.0 to 0.519 indicating the presence of wide range of genetic diversity at molecular level among the genotypes. Dendrogram was constructed using Dice similarity coefficients. The entries were divided into three groups on the basis of drawing phenon line at 0.20 coefficient of similarity level.Cluster A grouped together highly heat tolerant genotypes (PBW-343, HD-2967, BWL-9022 ), cluster B grouped moderately heat tolerant genotypes (Purulla, Seri-82, SALEMBO, KSG-1186 ) except CIANO-T-79 ( moderately heat susceptible) and cluster C grouped together highly heat susceptible genotypes (Sonara-64, SIDS, Sonalika) of wheat. Thus, molecular characterization revealed that genotypes under study were having genetically different levels of heat tolerance.