COMBINING ABILITY AND GENE ACTION OF Ifrassin, rapa L. (Toria)

Abstract

A 7 x 7 diallel experiment (excluding reciprocal) on Brassicu rapa L. (Turks,) was conducted to study the nature and magnitude of gene action and combining ability analysis and inheritance of some selected genotypes for seed yield and other related characters such as days to 50% liowering, days to maturity, plant height, primary branches per plant. secondary branches per plant, length of siliqua, siliquac per plant, seeds per siliqua, 1000-seed weight, seed yield per plant, harvest index and oil content. There were significant variations among the genotypes for all the characters studied. The components of variance for general combining ability (gca) and specific combining ability (sea) were highly significant for all traits indicating (lie role of both additive and non-additive eaniponents in the genetic system of these characters. Seed yield per plant was controlled by non-additive type of gene action. The parental genotype BARlsar-12(1 5) and SS-75(P6) were the best general combiners for seed yield. The parents Din-2(12). Tori-7(P), and BCWY-03(P) were desirable for earliness. Both parents Din-2(11,) were found stntable for dwarf plant type and higher number ofsiliquae per plant. the yellow seeded parental genotype BCWY-03(Pi ) was found to be the best general combiner for primary branches per plant, 1000 seed weight and oil content. The cross Din-2 x 13C-2I93(C). BCWY-03 x Din-2(Ci) and BCWY-03 x SS-75(C5) showed significant sea effects for seed yield. BCWY-03 x SS-75(C5) and BCWY-03) x l3ARlsar-12(C4) showed significant sea effects for 1000- seed weight. The cross l3ARlsar-12 x 55-75(C19) also showed significant effects for secondary branches per plant, siliquae per plant. 1000-seed weight and seed yield per plant.Tori-7 x SS-75(C14) and Din-2 x lori-7(127) showed significant effects for Iv earliness and dwarf plant type.The cross BCWY-03 x Din-2(Ci). BCWY-03 x SS- 75(C5), Tori-7 x 13C-I097(C). BARI-12 x SS-75(C19) and BARI-12 x l3C-1097(C20) were found to be best for seed yield per plant and siliquae per plant. Majority of the crosses showed high sca effects for seed yield involving high x low, low x low and high x high gca parents. Vr-Wr analysis relatig to graphical presentation of major genetic features was done for all the twelve characters. Over dominance was observed for primary branches per plant, secondary branches per plant, length of siliqua. siliquae per plant. seeds per siliqua, seed yield per plant and harvest index, while partial dominance was recorded tbr days to 50% liowering, days to maturity, plant height. 1000-seed weight and oil content. Component of variation and various genetic parameters such as degree of dominance, dominance ratio, narrow sense heritability eLe. were estimated. Positive and negative alleles were found in unequal proportion among the parents for all characters. Dominant gene action was predoniinant in most of the traits except days to 50% flowering, plant height, secondary branches per plant. 1000-seed weight and harvest index. Dominance and recessive genes were unequally distributed in the parents for all characters. High narrow sense heritability was observed for days to maturity, plant height and 1000-seed weight.