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ThesisItem Open Access Biochemical and molecular characterization of wheat genotypes for resistance against aphid (Rhopalosiphum maidis Fitch)(CCSHAU, Hisar, 2023-04-05) Yadav, Jayant; Maha SinghThe present studies entitled “Biochemical and molecular characterization of wheat genotypes for resistance against aphid (Rhopalosiphum maidis Fitch)” were carried out at field and lab facilities of the Crop Protection Division, ICAR-Indian Institute of Wheat and Barley Research, Karnal, Haryana from 2018-19 to 2020-21 Rabi cropping seasons. Most of the wheat varieties and wild genotypes were found to be either resistant or moderately resistant whereas none of the varieties and wild genotypes were found to be immune against aphid infestation. The susceptible check A-9-30-1 was most preferred by the aphids for survival whereas the varieties viz., DBW 90, DBW 187, DBW 303, WH 283, WH 1080, WH 1105 were found to be resistant with high nymphal mortality. Similarly, among the wild genotypes, the genotype 13993 was found to be most suitable for aphid survival whereas the genotype 3590 was highly resistant having increased nymphal duration, low fecundity and high mortality. The varieties viz., DBW 187 and WH 1105 were highly tolerant to aphid infestation with minimum reduction in seedling length and weight over control whereas A-9-30-1 was least tolerant. Similarly, in case of wild genotypes, the genotype 3590 had shown highest tolerance to aphid infestation while the genotypes PI 604172 and 13762 were least tolerant. In case of varieties, the highest alatae formation was observed in the genotype DBW 303 whereas lowest in the genotype A-9-30-1 while among the wild genotypes, the highest was observed in the genotype 3590 whereas lowest was noticed in the genotype 13993. Aphid infestation exhibited a significant increase in the total phenolics (TP), total proline (TPC), tannins, chlorophyll, phenlyalanine ammonia lyase (PAL), polyphenol oxidase (PPO), glutathione reductase (GR), hydrogen peroxide (H2O2), catalase (CAT), peroxidase (POX) and ascorbate Peroxidase (APX) content whereas non-significant change in total soluble protein (TSP) and total soluble sugar (TSS) content in the developing flag leaves as compared to the controlled conditions in both varieties and wild genotypes. Aphid nymphal mortality had significant positive correlation with TP, TPC, tannins, PAL, PPO, GR, H2O2, CAT, POX and APX content whereas negative correlation with TSP, TSS and chlorophyll content. AMOVA revealed that difference between Triticum spp and Aegilops spp was around 37 per cent of the total variation contributed by the whole germplasm. However, 63 per cent variation was attributed to diversity between individuals within a group. STRUCTURE analysis conceded the presence of four major sub-groups in the populations whereas two genotypes (UP 2425 and wild genotype 13993) were considered as admixtures. Out of the total significant MTAs identified, 22 MTAs were common during both the cropping seasons i.e., 2018-19 and 2019-20 and with the annotation of the markers from identified significant MTAs with genes, these can be employed with resistance breeding programs in wheat.