Dr. D. K. YadavaRANJIT SAROJT-112892024-10-252024-10-252023https://krishikosh.egranth.ac.in/handle/1/5810215861The response to selection in any crop improvement program depends on the degree of variance and heritability, and trait association. The objective of the current study was to explain variance, heritability components, genetic diversity, correlation among the traits, and marker trait association (MTA) in Indian mustard [ Czern & Coss] to recognize promising genotypes for effective breeding. Two hundred Brassica juncea (L). and eighty-nine diverse accessions of Indian mustard belonging to four continents were analyzed for yield and yield-related traits over two seasons (2017–2018 and 2018– 2019), using an alpha lattice design with two replications. The genetic variance was found to be significant (P ≤ 0.01) for the individual environments as well as under pooled analysis for all of the evaluated traits. High heritability combined with high genetic advance as percent of mean and genotypic coefficient of variation was observed for flowering traits, plant height traits, seed size, and seed yield/plant; hence, a better genetic gain is expected upon the selection for these traits over subsequent generations. Both correlation and stepwise regression analysis indicated that the main shoot length, biological yield, total seed yield, plant height up to the first primary branch, seed size, total siliqua count, days to flowering initiation, plant height at maturity, siliquae on the main shoot, main shoot length, and siliqua length were the most significant contributory traits for seed yield/plant. Genetic diversity using the phenotypic data revealed the genotypes grouped into five clusters and the most diverse cluster was cluster II (6.29). A high inter-cluster distance (D2 ) was recorded between cluster II and cluster IV (15.68), both the clusters can be used in hybridization breeding programs. Molecular genetic diversity of the 269 genotypes using 101 molecular markers (89 SSRs and 12 IPs) grouped the genotypes into five clusters. Structure analysis revealed that genotypes were grouped into two sub populations A and B, however, few genotypes had shown allele admixture representing genes carrying from both the sub-populations. Gene diversity revealed moderate diversity of the gene and the average number of alleles were also moderates in range. Linkage disequilibrium of the markers defined the low LD (0.127). Marker trait association revealed one marker (Na10A08) significantly associated with the seed yield per plant in pooled data analysis. Out of the total 101 markers, 20 markers were associated with the yield-related traits. IC-597867 was identified as promising genotype from the diversity study, which was the highest yielder, which can be used in future breeding programs for yield enhancement in Indian mustard.EnglishThesis