COMBINING ABILITY AND HETEROSIS IN F POPULATIONS DERIVED FROM 6×6 HALF DIALLEL CROSS OF MUSTARD (Brassica rapa)

Abstract

The experiment was conducted to evaluate the fifteen F 1 lines derived from 6×6 half diallel cross of Brassica rapa for yield and yield components. Six (6) parents of mustard were mated using half 6×6 diallel fashion during Rabi season 2017-18 and then evaluated the combining ability and heterosis of fifteen F 1 hybrids over two check varieties BARI sharisha-14 (CV1) and local variety Maghi (CV2) at research farm of Sher-e-Bangla Agricultural University, Dhaka during Rabi season 2018-19. The analysis of mean performance showed that the hybrid combination P2×P6 (80.00) matured with the lowest growth duration, while the cross P1×P4 and P4×P6 had taken the longest duration. The hybrid P3×P5 produced the highest number of seeds per silique, while P2×P4 produced the lowest number of seeds per silliqua. The heaviest or the boldest seeds were produced by the hybrid P3× P5 (4.00 g). Again, the highest seed yield per plant was observed in the hybrid P1×P3 (7.40 g), while the lowest seed yield per plant was observed in hybrid P2 ×P4 (2.33 g). The variances for general combining ability (GCA) and specific combining ability (SCA) were found significant for all the characters which indicated that both type of gene actions such as additive and non-additive were involved for the controlling of yield and yield related characters in the hybrid progenies. GCA variances were higher in magnitude than SCA for all the characters except no. of primary branches per plant, number of siliqua per plant and seed yield per plant indicating the superiority of non-additive or dominant gene effects for the inheritance of these traits. The analysis of GCA revealed that parents P1, P3 and P5 were the best general combiner for yield related character, while parents P6 and P1 for earliness and tall plant type. The SCA analysis revealed that crosses P1×P3, P2×P6 and P4×P6 exhibited maximum positive effects for yield related characters. In heterosis analysis, the test hybrid combinations viz., P1×P2, P1×P6, P2×P3, P2×P4, P2×P5, P2×P6, P3×P4, P3×P6, P4×P5, P4×P6 and P5×P6 manifested the negative significant heterosis over CV1 but none of the crosses showed significant negative heterosis over CV2 as well as over their better parent for days to first flowering. Again, none of the crosses showed significant negative heterosis over CV1 and BP for days to maturity. The cross combinations viz., P1×P3, P1×P5 and P1×P6 showed positive standard heterosis over CV1 and CV2 for yield and yield contributing characters such as siliqua length, no. of seeds per siliqua, thousand seeds weight and seed yield per plant. Interestingly, only hybrid P1×P3 showed standard hetersosis over both the check varieties for seed yield. Considering the standard heterosis for yield and yield attributes, the tested hybrids viz., P1×P2, P1×P3 and P1×P5 might be selected as superior B. rapa hybrid lines. Moreover, the hybrid lines viz., P1×P4, P2×P5, P2×P6, P3×P4, P3×P5, P3×P6, P4×P5 and P4×P6 could also be selected as potential lines because these hybrids could produce transgressive segregants in advanced or later generations.