GENETICS OF QUANTITATIVE TRAITS IN BREAD WHEAT (Triticum aestivum L.) OVER ENVIRONMENTS 2529
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Date
2018-03
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JAU,JUNAGADH
Abstract
The present investigation entitled “Genetics of quantitative traits in bread wheat (Triticum aestivum L.) over environments” was carried out with a view to estimate heterosis, combining ability and gene action, genetic components of variance, genotype x environment interaction and stability parameters for grain yield per plant and 13 different quantitative traits in bread wheat. The experimental materials comprised of nine parents (NW 5013, DBW 90, PHSC 5, GW 2010-287, BW 5872, QLD 65, QLD 46, RAJ 4238 and GW 496), their thirty-six F1 hybrids and one standard check variety GW 366 were evaluated in three different environments [Early (25th October), timely (15th November) and late sowing (5th December)] designated as environment I (E1), environment II (E2) and environment III (E3), respectively, in randomized block design with three replications during rabi 2016-17 at Sagadividi Farm, Department of Seed Science and Technology, College of Agriculture, Junagadh Agricultural University, Junagadh. Five competitive plants per genotype in each replication in each environment were selected randomly for recording observations on different characters viz., plant height (cm), number of effective tillers per plant, length of main spike (cm), peduncle length of main spike (cm), number of spikelets per main spike, number of grains per main spike, grain weight per main spike (g), 1000 grain weight (g), grain yield per plant (g), biological yield per plant (g) and harvest index (%), while observations on days to heading, grain filling period and days to maturity were recorded on plot basis. The data were analyzed for heterosis and combining ability (Method-II, Model-I of Griffing, 1956), while the genetic components of variation were estimated according to Hayman (1954) and G x E interactions and stability parameters were calculated following the model of Eberhart and Russell (1966).
The analysis of variance for genotypes, parents and hybrids indicated the existence of considerable amount of genetic variability amongst genotypes, parents and hybrids for seed yield per plant and most of the characters under study. The comparison of parents vs. hybrids across the environments, in general, revealed the existence of heterosis. The interaction of genotypes with the environments indicates the non-linear response of the genotypes to the change in the environment.
No specific consistency was observed with regards to heterosis for grain yield and yield component in different crosses. On pooled basis, four hybrids over better parent and one hybrid over standard check variety exhibited significant and positive heterosis. NW 5013 × BW 5872 in E1, PHSC 5 × GW 2010-287, DBW 90 × BW 5872 and NW 5013 × QLD 65 in E2, NW 5013 × QLD 65, DBW 90 × GW 2010-287, PHSC 5 × GW 2010-287 and DBW 90 × BW 5872 in E3 and PHSC 5 × GW 2010-287 in pooled results were the best significant and positive cross combinations with respect to standard heterosis for grain yield per plant.
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The significant difference of GCA and SCA indicated that both additive and non-additive gene effects played an important role in the genetic control of the traits studied. The ratio of σ2gca / σ2sca was lesser than unity indicates the preponderance of non-additive gene action for all the characters studied in individual environments as well as across the environments. On pooled basis, the parents PHSC 5, QLD 46 and Raj 4238 were found to be good general combiners for grain yield per plant and possessed high concentration of favourable genes as indicated by significant and positive GCA effects for these parents. Considering the overall performance of hybrids across the environments for grain yield per plant, eight hybrids viz., PHSC 5 × GW 2010-287, DBW 90 × GW 2010-287, DBW 90 × BW 5872, Raj 4238 × GW 496, DBW 90 × GW 496, NW 5013 × DBW 90, NW 5013 × QLD 65 and GW 2010-287 × QLD 65 manifested significant positive sca effects. The three best specific crosses involved good x poor and average x poor general combiners.
Relative magnitude of dominance component was found to be higher than additive component for most of the traits in all three environments, indicates that studied characters were mostly under the control of dominance variance. The average degree of dominance (H1/D)1/2 indicated over dominance type of gene action in individual environments for all the traits studied except in E2 for number of effective tillers per plant. The distribution of genes with positive and negative effects (H2/4H1) in the parents was observed nearly symmetrical for grain yield per plant and all the characters studied. The estimates of KD/KR ratio was more than unity indicated the excess of dominant alleles in parents for all the characters studied except for number of effective tillers per plant in E1, for peduncle length of main spike in E1 and E2, for number of spikelets per main spike in all three environments, and for number of grains per spike and biological yield per plant in E2. The ratio of h2/H2 indicated that there was one group of genes responsible for controlling all the traits studied. The low to moderate estimates of narrow sense heritability was depicted for most of the traits in individual environments indicated that the characters studied were much influenced by the environments.
Two parents (NW 5013 and QLD 46) and twelve hybrids (PHSC 5 × GW 2010-287, DBW 90 × GW 2010-287, DBW 90 × BW 5872, NW 5013 × QLD 65, BW 5872 × QLD 65, GW 2010-287 × BW 5872, Raj 4238 × GW 496, QLD 65 × QLD 46, GW 2010-287 × QLD 46, BW 5872 × QLD 46, BW 5872 × Raj 4238 and GW 2010-287 × Raj 4238) expressed their stability across the environments for grain yield per plant due to their high per se for grain yield per plant, non-significant regression coefficient (bi) and deviation from linear regression (S2di).
On the basis of per se performance, stability and general combining ability estimates of the parents for grain yield and its components in individual environments as well as across the environments, parents PHSC 5, QLD 46, NW 5013 and Raj 4238 may be used in heterosis breeding for isolating desirable types in bread wheat. On the basis of per se performance, stability, heterotic response, specific combining ability estimates and gene action involved in the expression of grain yield and its components in individual environments as well as across the environments, cross combination PHSC 5 × GW 2010-287 appeared to be the most suitable for exploitation in practical plant breeding programme in wheat, as this hybrid across the environments ranked first with respect to grain yield per plant (18.88 g) with significant standards heterosis (18.00 %) and significant sca effects for grain yield per plant, and was found to be stable for grain yield per plant, grain filling period, length of main spike, peduncle length of main spike, number of spikelets per main spike and harvest index. Therefore, this cross could be exploited for the improvement of grain yield and specific yield contributing characters in wheat.
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GENETICS AND PLANT BREEDING