GENETIC ANALYSIS ON YIELD, OIL CONTENT AND QUALITY CHARACTERISTICS OF SELECTED Brassica rapa L. GENOTYPES

Abstract

The investigation was carried out at the experimental field and in the Biochemistry and Agricultural Chemistry and Environmental Science laboratory of Sher-e-Bangla Agricultural University, Dhaka during Nov/2017 to Dec/2021 with seven selected Brassica rapa genotypes to develop elite breeding lines with high yield potential, short duration and high oil content with better quality. BARI Sar-6 had the highest yield (8.41 g plant -1 ) but had very long duration (110 days), while Tori-7 had the lowest yield (4.25 g plant -1 ) with short duration (81.66 days), on the other hand Brown Special matured early (80.66 days) with moderate yield (5.88 g plant -1 ). Most of the F s were intermediate type between their parents for morphological characteristics and performed better than their both parents for most of the quantitative traits. Tori-7 × Brown Special matured early in 80 days, while the highest yield (27.67 g plant -1 )

1 had recorded in Tori-7 × Yellow special. The highly significant and the highest negative heterosis for maturity had recorded in BARI Sar-6 × Brown Special over the better parent (-23.33%) and in BARI Sar-6 × BARI Sar-17 over the mid parent (-13.22%). For yield plant , Yellow Special × Tori-7 showed the highly significant and the highest positive heterosis over both the parents (352.37% and 245.01% respectively). Considering the highest positive (except earliness) and the highly significant GCA effects, Brown Special was the best general combiner for earliness and yield plant -1 , while based on SCA effects, the cross BARI Sar-6 × Brown Special was the best for earliness and BARI Sar-15 × Brown Special was the best for yield plant -1 . Therefore, these genotypes might be used for further improvement of these traits. Generation mean analysis revealed that, F 1 s were superior over their both parents but F s means indicated inbreeding depression in most cases. BC 2 performed better than BC 1 2 in most of the crosses for yield plant -1 . The significant scaling tests for most of the traits across the crosses indicated the presence of epistasis but insignificant χ2 values in most cases indicated the absence of epistasis and thus, six-parameter model (Hayman, 1958) had suggested to explain the nature of gene actions. Significant negative additive gene effects for most of the traits across the crosses indicated non-additive gene action and selection might be ineffective but in those cases significant positive additive gene effects had found selection might be effective. While heterosis breeding could be explored for significant positive dominance gene effects in most other cases. However, where, both additive and dominance gene effects were significant and positive, reciprocal recurrent selection might be suggested. For oil content, the parent - Yellow Special, F 1 - Brown Special × Yellow Special, F 2 - BARI Sar-14 × Yellow Special and in both BC

and BC - Tori-7 × BARI Sar-14 contained the highest amount of oil, 45.05%, 39.04%, 37.71%, 38.98% and 38.57 % respectively. Among the parents - Tori-7, in all F 2 1 , F 2 and BC - Tori-7 × Yellow Special and among BC - Yellow Special × BARI Sar-6 contained the highest amount of poly unsaturated fatty acid, 16.98%, 19.27%, 21.54%, 21.57% and 16.47 % respectively. Among the parent - Tori-7, in all F 1 , F 2 2 and BC 1 -Tori-7 × Yellow Special and among BC - Yellow Special × BARI Sar-6, contained the lowest amount of erucic acid, 44.97%, 45.37%, 45.42%, 45.49% and 46.67 % respectively. So, these genotypes might be used for further development of these traits.