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Showing 3 results for General Combining Ability
Mohtasham Mohammadi, Mozafar Roustaie,
Volume 2, Issue 2 (3-2016)
Abstract
For development of high yield wheat cultivars, this study was conducted to estimate the general combining ability (GCA) of parents, specific combining ability (SCA) of hybrid progenies, heritability and heterosis of grain yield and some agronomic traits. A partial diallel crosses which obtained in a set of six wheat genotypes were sown in randomized complete block design at Gachsarann agricultural research station in 2013-14 growing season under dryland condition. The results of this study revealed a significant difference among the genotypes for all of the traits that indicating considerable genetic variation. Significant effects of GCA and SCA indicated role of additive and non-additive gene action in the control of all considered traits. The mean square ratio of GCA to SCA and Baker genetic ratio showed a preponderance of non-additive gene action for all of the studied traits. Broad-sense heritability was high (0.67-0.99) for all of them, which indicated the role of genetic factors compared with non-genetic factors for controlling of these traits. Narrow-sense heritability was low to moderate (0.06–0.37). Among the parents, Koohdasht was the best general combiners for early growth vigor, days to maturity, spike length, peduncle length, flag leaf extrusion and grain yield. The Koohdasht × DAMARA-6 hybrid showed the best specific cross for days to heading, days to maturity, grain filling period, plant height, chlorophyll content, canopy temperature, grain length and grain yield. These hybrids showed positive and significant heterosis for grain yield, chlorophyll content and grain length and negative heterosis for plant height. It is expected to produce desirable segregants and could be exploited successfully in wheat improvement programs. In addition, because of preponderance of non-additive gene action for studied traits, particularly in the early generations, efficiency of genetic selection was low and selection for genetic improvement of these traits must be retraced in advanced generations.
Dr Mohammad Motamedi, Ms Parviz Safari,
Volume 4, Issue 2 (3-2018)
Abstract
Drought stress is one of the most important factors involved in reducing wheat production and identifying genetic structure and gene action type in controlling grain yield in water stress condition is essential for choosing appropriate breeding methods. In this study, 9×9 one way diallel crosses were used to study the genetic structure of wheat grain yield at stress and non- stress conditions. Combining ability analysis by the second Griffing method for both conditions resulted in significant GCA and SCA variances, representing grain yield may be controlled by additive and non- additive effects of genes. The results of applying combining ability analysis indicated that among the parents, genotypes Ghods and Bam had the highest GCA for grain yield and the best specific crosses were Arg × Ghods, Navid × Moghan, Bam × Alvand (for both irrigation regimes) and Bam × Ghods (in stress condition). Biplot analysis of diallel data was used to display GCA and SCA for parents and to determine heterotic groups and the best crosses. In general, according to the results, Bam, Ghods and Arg were tolerant cultivars and had the ability to maintain yield in drought stress condition as well as to transfer these properties to the hybrids. So these genotypes can be used to improve stress tolerance in breeding programs.
Amir Gholizadeh, Hamid Dehghani, Mostafa Khodadadi,
Volume 5, Issue 1 (9-2018)
Abstract
In any breeding program, knowledge of the nature of gene action involved in the inheritance of traits is a basic requirement. In this research, diallel crosses progenies of six coriander landrace were evaluated in F1 and F2 generations. The genotypes were evaluated in different irrigation conditions in three separate experiments, in which each experiment was conducted in a randomized complete block design with three replications during the growing season of 2016. Results of genetic variance analyses revealed significant mean squares of general and specific combining ability for all traits, indicating the importance of additive and non-additive genetic effects for these traits. Additive gene actions played a more important role in controlling of plant height, leaf number, branch number and biological yield, whereas the role of non-additive gene actions was more conspicuous than those of additive gene actions in controlling of harvest index and fruit yield. Therefore, providing superior hybrids using breeding methods based on progeny test will be effective to improve these traits. Also, among selected parents, P4 parent in normal irrigation and moderate water stress and P6 parent in sever water stress were the best parents for crosses in the development of high-yield varieties in coriander.
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