Heterosis and Combining Ability Analysis for Yield and Its Components in Bread Wheat (Triticum Aestivum L.)

Abstract

The present study entitled "Heterosis and combining ability analysis for yield and its components in bread wheat (Triticum aestivum L.)" was carried out in the Department of Genetics and Plant Breeding, Sardar Vallabhbhai Patel University of Agriculture and Technology, Meerut, during 2012-2013. The experimental materials for the present study involved 10 genetically diverse wheat varieties namely, HD-2967, PBW-502, RAJ-3765, HD-2733, UP-2425, WH-1021, DBW-17, HD-2864, RAJ-4083 and UP-2565. These parental lines were mating in diallel fashion excluding reciprocals during the rabi season of2012-2013, at the crop research centre, Sardar Vallabhbhai Patel University of Agriculture and Technology, Meerut. The parents and their 45 F Is were also grown in the next year during radi season of 2013-2014 under irrigated conditions A in randomized block design with three replications. Positive and significant value ofF component of variance for 7 traits namely, spike length, number of spikelets per spike, number of grains per spike, number of p.r oductive tillers per plant, harvest index, 1000 grains weight and gluten content, whereas, positive value of F component were for 3 traits namely, plant height, peduncle length and flag leaf area in F 1 generation which revealed that the dominant genes are responsible for the inheritance of these traits .. The estimates of average degree of dominance expressed as (H 1/ D )112 were found higher than unity in F1s for 9 traits namely, number of spikelets per spike, number of grains per spike, number of productive tillers per plant, biological yield per plant, grain yield per plant, harvest index, I 000 grain weight, flag leaf area, and gluten content which indicated presence of over dominance while traits, days to 50 % flowering, days to maturity, plant height, peduncle length, spike length expressing average degree of dominance as lesser than unity and greater than zero which • A indicated partial dominance. The proportion of dominant and recessive alleles, expressed by the ratio of (4 D H1) 112 + fr /(4 D H1) 112 - fr were found more than unity in the parents for I 0 traits namely, plant height, peduncle length, spike length, number of spikelets per spike, number of grains per spike, number of productive tillers per plant, harvest index, I 000 grain weight, flag leaf area and gluten content showed that dominant allele were more frequent than recessive allele in the inheritance of these characters in F1 generation whereas this ratio was less than one for 4 characters namely, days to 50% flowering, days to maturity, biological yield and economical yield which indicated that more recessive alleles are present in the parents for these traits. The estimated value of ratio (h2/H2) which is a measure of a set of genes showing dominance was observed more than one (unity) for 8 traits namely, days to 50% flowering, days to maturity, number of spikelets per spike, number of grains per spike, number of productive tillers per plant, biological yield per plant, grain yield per plant and harvest index in F1 generation which indicated that more than one major gene groups are responsible for inheritance of these characters whereas the value of this ratio is less than unity for the other characters naniely, plant height, peduncle length, spike length, I 000 grains weight, flag leaf area and gluten content indicated the involvement of single gene group in the inheritance ofthese characters.The genotypes NW 1076, UP 2425, NW 1014, K 7903 and K 9423 were identified as best general combiners while, cross combinations namely, HD-2967 x UP-2425, UP-2425 x UP-2565, PBW-502 x UP-2425, HD-2967 x RAJ-4083, PBW-502 x WH-1 021 were identified as best specific combiners for yield and its contributing traits. These cross combination may be expected in heterosis breeding programme and developing so genotype having broad genetic base by multiple crossing programme. The results obtained from the present study showed less than I 0 % PCV and GCV for all the traits. The high heritability (narrow sense) coupled with medium genetic advance (in % over parental mean) was observed only for flag leaf area and peduncle length. It indicated that heritability might be due to additive gene effects and direct selection for these traits may be effective. Grain yield per plant had positive and highly significant correlation with number of spikelets per spike, number of grains per spike, number of productive tillers per plant, biological yield per plant, harvest index, I 000 grain weight and gluten content. The significant association of these characters with grain yield per plant reflected that by improving these traits, grain yield per plant could be improved. Path coefficient analysis revealed that harvest index display high order of direct effect on grain yield per plant followed by biological yield per plant, ~e ~n;;, gluten content, I 000 grains weight, number of spikelets per spike and flag leaf area.