Chhuneja, ParveenPreeti Kumari2022-02-042022-02-042020Preeti Kumari (2021). Marker assisted introgression of grain size QTL from Aegilops tauschii Coss. to Triticum aestivum L. (Unpublished Ph.D. Dissertation). Punjab Agricultural University, Ludhiana, Punjab, India.https://krishikosh.egranth.ac.in/handle/1/5810181705Hexaploid wheats shows constrained genetic diversity which can be broadened by exploiting the wild relatives of wheat for introgressing the novel genes or alleles. Aegilops tauschii, the diploid Dgenome progenitor of hexaploid wheat, can be used to increase the genetic diversity both for improving grain yield and nutritional quality of bread wheat. Grain size is one of the important variables influencing the grain yield. To achieve higher wheat yields, breeding efficiency needs to increase which can be done through biotechnological interventions. The present study aimed to validate the markers linked to the QTLs for grain weight, grain length and grain width and to use the markers for marker assisted transfer of these traits from Ae. tauschii to hexaploid wheat using T. durum (PBW114) as bridging species. Four hundred and ninety-five wheat- Ae. tauschii advance backcross introgression lines (GWILT) derived form 13 different Ae. tauschii donor accessions (pau9793, pau9809, pau14328, pau14339, pau14158, pau14169, pau14170, pau14200, pau14232, pau3747, pau3752, pau3760, pau9810) and two recipient wheat cultivars PBW550 and PBW621 were evaluated for various agronomic and quality traits for four consecutive crop seasons (2015-16 to 2018-19). In each generation selections were made and phenotypically superior lines were progressed further. Total of two hundred and forty-nine highly promising lines were identified which showed better performance in all the four years. These lines offer a good opportunity to study the genetic loci which may be responsible for variation in grain size and other related traits. The pooled correlation coefficient among traits for wheat-Ae. tauschii AB introgression lines reveals a positive correlation of thousand grain weight (TGW) with grain filling duration (GFD), length (LN), width (WD) and yield per plot (YD) but grain number per spike GNpS showed negative correlation with TGW. Tiller number per meter showed positive correlation with overall yield. TGW depends more on grain width than grain length. Seventeen introgression lines derived from Ae. tauschii accessions pau14169, pau3760, pau9809 showed high level of resistance for stripe rust in the range of 5MR-10MR. In previous study, three Ae. tauschii accessions pau14232, pau14231 and pau9796 which were found to have high grain size were used in present study for transfer of grain size QTLs to hexaploid wheat cv. PBW725 and advance breeding line BWL4478 using T. durum (PBW114) as bridging species. Two molecular markers GS7D and CWI21 which have been reported to be associated with grain size were used in the present study for marker assisted selection at different stages (BC1F1, BC2F1, and BC2F2) and selection of grain size introgressions. One hundred and seventy-one introgression lines in BC2F2 generation were developed and evaluated genotypically as well as phenotypically for grain weight. All these lines showed significant grain weight improvement over the respective recurrent parent PBW725. The selected introgression lines can further be used in wheat improvement programme and mapping yield component traits.EnglishThesis