Genetic Analysis and Genotype by Environment Studies in Maize

Abstract

Five white kernel maize inbred lines were crossed in a complete diallel fashion during spring season 2011 at Cereal Crops Research Institute (CCRI), Pirsabak - Nowshera, Khyber Pakhtunkhwa, Pakistan. The resulting 20 F1 hybrids, five parental inbred lines and two checks (OPV 'Jalal' and 'Pioneer hybrid 30k08') were evaluated during subsequent summer season 2011 through field experiments at a) CCRI - Nowshera, b) University of Haripur, Haripur, c) ARS, Baffa - Mansehra, and d) ARS, Mingora - Swat, Khyber Pakhtunkhwa, Pakistan. All the experiments at four different locations were laid out in a randomized complete block design with three replications. Present research was carried out with the objectives to study the genotype by environment interaction (GEI), gene action, heterosis and correlation. Genotypes, locations and GEI showed highly significant differences for most of the studied traits. For days to physiological maturity, F1 hybrid FRHW-2 × FRHW-1 took minimum days at CCRI (80.33 days) and Haripur (82.67 days) and showed early maturity. The F1 hybrid PSEV3 × FRHW-2 at Swat and its reciprocal at Mansehra mature in 84.33 and 102.33 days, respectively. For grain yield, F1 hybrid FRHW-1 × SWAJK-1 at Mansehra (14482 kg ha-1) and Swat (15205 kg ha-1) produced maximum grain yield than all other genotypes. However, the F1 hybrids SWAJK-1 × FRHW-1 at Haripur (11277 kg ha-1) and PSEV3 × FRHW-3 (9238 kg ha-1) and PSEV3 × FRHW-1 (9297 kg ha-1) at CCRI showed maximum grain yield. Overall, the above F1 hybrids showed significant earliness and increased grain yield than other genotypes which could be used in future breeding programms. Additive dominance model was adequate/partially adequate for almost all the traits except one/two traits for which the genetic model was inadequate at all the locations. According to Hayman's genetic analysis, key components of genetic variance i.e. additive (D) and dominance components (H1, H2) were significant for majority traits at all the locations. However, through comparison of the components of genetic variance, average degree of dominance and Vr/Wr graphs, the dominance components were predominant and overdominance type of gene action played important role in inheritance and phenotypic expression of the majority traits at all the locations. High broad sense heritability estimates ranging from 0.88 to 0.99 were recorded for all the traits/locations except prolificacy at Haripur, which showed moderate broad sense heritability (0.66). Except physiological maturity, the narrow sense heritability for various traits was low to medium and ranged from 0.10 to 0.35 at CCRI, 0.01 to 0.37 at Haripur, 0.10 to 0.64 at Mansehra and 0.01 to 0.56 at Swat. For physiological maturity, the narrow sense heritability was high and ranged from 0.94 to 0.97 at all the locations. Desirable moderate to high genetic gain values were observed for all traits. Majority of the F1 progenies showed desirable and significant negative mid and better parents, economic and commercial heterosis for earliness traits at all locations. For earliness traits, F1 hybrid FRHW-1 × FRHW-3 at CCRI, FRHW-1 × PSEV3 at Haripur, F1 hybrids FRHW-2 × PSEV3 and PSEV3 × FRHW-1 at Mansehra and FRHW-2 × FRHW-3 at Swat showed desirable and significant negative mid and better parents, economic and commercial heterosis. Overall, on the basis of earliness, majority of the F1 hybrids revealed significant negative economic and commercial heterotic values for physiological maturity at various locations i.e. 15 and 18 F1 hybrids at CCRI, 13 and 19 at Haripur, 13 and 19 at Mansehra, and 17 and 19 hybrids at Swat, respectively. These F1 hybrids showed significant earliness than other F1 populations and parental genotypes which can be used in future breeding programmes for developing early maturing hybrids and cultivars with good yield potential. Large number of the F1 hybrids revealed significant positive heterotic effects for grain yield and most of the yield contributing traits at Swat, followed by Mansehra, Haripur and CCRI. Majority of the F1 hybrids revealed significantly positive mid and better parent heterotic effects for plant height, primary leaf area, fresh ear weight, ear diameter, ear length, grain rows per ear, grains per row, 1000-grain weight, shelling percentage, grain yield, biological yield, harvest index and grain yield efficiency at all the locations. For grain yield, F1 hybrids PSEV3 × FRHW-1 and PSEV3 × FRHW-2 at CCRI, FRHW-2 × FRHW-1 and SWAJK-1 × FRHW-1 at Haripur, FRHW-1 × SWAJK-1 at Mansehra and FRHW-2 × FRHW-3 and FRHW-1 × SWAJK-1 at Swat showed desirable and significant positive mid and better parents, economic and commercial heterosis. Therefore these F1 hybrids could be used in further breeding programs. Grain yield revealed negative genotypic and phenotypic correlations with majority of the earliness traits while it showed significantly positive relationship with yield contributing traits at all locations. Due to nonadditive gene action, different types of heterosis, high broad sense heritability, and screening of F1 hybrids through genotype by environment interactions, the promising F1 hybrid FRHW-1 × SWAJK-1 at Mansehra and Swat, SWAJK-1 × FRHW-1 at Haripur and PSEV3 × FRHW-3 and PSEV3 × FRHW-1 at CCRI produced maximum grain yield and are recommended as hybrid crop to increase the maize grain yield. For earliness, the F1 hybrid FRHW-2 × FRHW-1 at CCRI and Haripur, PSEV3 × FRHW-2 at Swat and FRHW-2 × PSEV3 at Mansehra showed early physiological maturity than all other genotypes. Therefore, the above promising F1 hybrids can also be used in future breeding programs for production of early maturing and high yielding maize hybrids/cultivars.