Evaluation of genetic variability, heritability, and character association of yield and yield contributing traits in BC ₂ populations of Brassica rapa L.

Background : The improvement of Brassica rapa for a higher yield and shorter growth duration depends on the availability and effective utilization of genetic variability, as well as interrelationships between yield and its associated traits. Backcrossed (BC) populations are regarded as a valuable resource for analyzing genetic parameters to pinpoint potential selection criteria aimed at improving yield. Methods : The experiment was carried out at Sher-e-Bangla Agricultural University, employing 20 BC 2 populations, derived from the advancement of several inter-varietal crosses. The study was set up using a randomized complete block design with three replications. Data were recorded on various yield-and-contributing traits and analyzed to estimate variability, heritability, genetic advance, correlation, and both direct and indirect influences through path coefficient analysis. Results : The characters displayed significant variations among the genotypes. For each character, phenotypic variance exceeded genotypic variance. The number of primary and secondary branches per plant, siliqua length, days to 50% flowering, days to 80% maturity, thousand-seed weight, and seed yield per plant had the least phenotypic and genotypic variance. The number of secondary branches per plant and the seed number per siliqua demonstrated significant heritability and genetic advance, indicating additive gene action and natural selection possibilities. The plant’s height, number of siliquae per plant, and thousand-seed weight correlated strongly with yield per plant, both phenotypically and genotypically. Consequently, it is essential to take these factors into consideration to improve the intricate characteristic of yield per plant. The genotypic correlations surpassed the phenotypic correlations for all traits, demonstrating their strong heritability and their relevance in selective breeding. Path coefficients revealed that siliqua length, number of siliquae per plant, thousand-seed weight, and days to maturity positively influence seed yield per plant. This suggests that direct selection can boost seed yield. Conclusions : The study develops selection indices aimed at enhancing crop improvement initiatives through the identified traits. This comparative analysis highlights two BC 2 populations, G20 and G17, which have shown high potential for further assessment based on their outstanding performance in several key metrics, including the number of siliquae per plant, siliqua length, thousand-seed weight, and seed yield per plant.