Graphical Analysis of Genetic Variation for Pod Yield and Earliness in Garden Pea

Abstract

Seven diverse genotypes of garden pea were crossed in a diallel mating design (excluding reciprocals) to infer about the genetic architecture of pod yield and earliness following Haymans' approach. Both the GCA and SCA variances were found significant for all the traits studied. The predictability ratio (σ²SCA/σ²GCA) was more than unity for all the traits studied except for days to 50 % flowering. The values of observed regression coefficient 'b' were low in magnitude and deviated from unity for days to first picking, shelling percentage, pods per plant, plant height and pod yield per plant. The regression line intersected Wraxis below the point of origin which indicated the presence of overdominance. The scatter of array points along the regression line clearly indicated that the parental genotypes used in the present investigation were genetically diverse. The parental arrays, DPP 941806 and Pb89 possessed most of the dominant genes with positive effect, whereas, the parents DPP3 and DPP LMR41 had the recessive genes with increased effect on pod yield and its related traits. Both additive (D) and nonadditive (H₁ , H₂) components were found significant for all the traits except additive component for pod yield per plant, shelling percentage and days to first picking. The mean degree of dominance revealed the presence of over dominance for all the traits which was probably due to the predominant role of nonadditive genetic variation. The equal distribution of positive and negative genes in the parents was observed for days to 50 % flowering, pods per plant and shelling percentage. Low narrow sense heritability estimates were observed for pod yield per plant, pods per plant, days to 50 % flowering and days to first picking.