COMBINING ABILITY AND GENE ACTION IN A 7x7 F2 HALF DIALLEL POPULATION OF Brassica napus L.

Abstract

Twenty one F2 progenies derived from a 7x7 diallel crosses along with parents were evaluated at experimental site of Sher -e- Bangla Agricultural University for ten yield and yield contributing traits. Due to significant genotypic effects for all the traits, genetic analyses were performed on F2 progenies including analyses of combining ability and genetic components. Out of 21 Fjs, the combinations Nap-20 12x Nap-2022, Nap_2037xNap.-206, Nap-I 79xNap- 206 and Nap-248xNap-2012 showed desirable negative combining ability for the characters of shorter plant height. Nap_248xNap-179. Nap-2057xNap20I2 were good specilic combiner for early flowering. The hybrid Nap248xNap1 79 was the best for early flowering. The cross Nap_2037xNap_2022 was the best for number of primary branches/plant, number of secondary branches, number of siliquae/plant and yield/plant. The cross Nap-206 x Nap-2057 and Nap_248xNap_2057 were the best for siliqua length and number of seeds/siliqua, respectively. For 1000 seed weight the hybrids Nap-I 79xNap_2057 combination is best. The crosses Nap_248x Nap-2022 and Nap_179x Nap-206 were found to be the best for higher oil content %. The parent Nap-2022 was the best general combiner for early flowering, number of primary branches/plant. The parent Nap-248 was the best for 1000 seed weight. Two parents Nap- 179 and Nap-257 were good general combiner for oil content %. On the basis of avcragc score and rank position, the hybrid Nap2037xNap2022 was the best spccific combiner for most of the important characters. The mean sum of square due to SCA was significant for all traits indicating that the non-additive gene actions were predominant for the expression of these characters. The significant mean sum of square due to GCA was also observed for the traits indicating that non additive gene actions were also prevailed. The higher magnitude of SCA variance was observed than that of GCA variance for all the traits. The Vr-Wr graph indicates over dominance (a>O) for number of primary and secondary branches per plant, number of seeds per siliqua and oil content. Partial dominance (a>0) was observed for plant height, days of flowering, number of siliquae per plant, siliqua length, thousand seed weight and seed yield per plant.