POPULATION SELECTION IN F 3 AND BACKCROSS GENERATION OF Brassica rapa L.

Abstract

At the experimental field of Sher-e-Bangla Agricultural University in Dhaka, an

experiment was undertaken from November 2021 to February 2022 with 46 populations of Brassica rapa L. (38 F 3 and 8 BC 2 F 2 populations), to estimate genetic variability, correlation, heritability, genetic advance, and direct and indirect effects of different traits for seed yield contributing traits. The analysis of variance exhibited significant variations in all the attributes among all populations. Days to first flowering, number of primary branches per plant, days to 80% maturity, siliqua length, and thousand seed weight exhibited the least difference between genotypic and phenotypic variance, indicating that the environment less influences these traits. The number of secondary branches per plant, the number of siliquae per plant, number of seeds per siliqua, and seed yield per plant however, were found to have high genotypic and phenotypic coefficients of variation. Days to first flowering, days to 80% maturity, number of secondary branches per plant, number of seeds per siliqua, siliqua length, and thousand seed weight all showed high heritability with low genetic advance which could further be improved by subsequent generation advancing. Number of secondary branches per plant, number of siliquae per plant, number of seeds per siliqua, and thousand seed weight showed high heritability along with high genetic advance in percentage of mean. In breeding program, heritability accompanied by higher genetic advance as percentage of mean is considered useful in identifying high yielding genotypes. According to a correlation study, at both the phenotypic and genotypic levels, seed yield per plant was positively and significantly associated with days to 80% maturity, plant height, number of primary and secondary branches per plant, number of siliquae per plant, and siliqua length. Through path coefficient analysis, it was found that there was a direct positive effect on seed yield per plant in terms of days to 50% flowering, days to 80% maturity, number of primary branches per plant, number of secondary branches per plant, number of siliquae per plant, siliqua length, and number of seeds per siliqua. Characters like days to 80% maturity, plant height, number of primary branches per plant, number of secondary branches per plant, number of siliquae per plant, siliqua length, number of seeds per siliqua, and seed yield per plant would be considered while making the selection process. Among 46 populations (38 F 3 and 8 BC 2 F 2 populations), on the basis of short duration 5 F 3

populations such as G4 (81.67 DAS), G16 (81.67 DAS), G26 (80.67 DAS), G27 (82.33 DAS), G28 (80.67 DAS) can be recommended. For high yield 2 F 3 population such as G37 (9.49 g), and G38 (10.08 g), and 3 BC 2 F 2 populations such as G40 (12.31 g), G45 (10.62 g), and G46 (9.39 g) can be recommended for evaluation trial.