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Showing 7 results for 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.
Mehdi Rahimi, Maryam Abdolinasab,
Volume 6, Issue 2 (3-2020)
Abstract
Biochemical and physiological traits are affected by environmental stresses and therefore the breeding of these traits will play an effective role in stress tolerance. In this study, hybrids of five S7 lines of maize in a 5 × 5 half-diallel design were investigated in order to study the combining ability of biochemical and physiological traits of maize at the Research Farm of Graduate University of Advanced Technology, Kerman, Iran during the 2017-18 crop year based on randomized complete block design with three replications. The results of analysis of variance by fourth Griffing's method showed that the general (GCA) and specific (SCA) combining ability variances were significant for protein, proline, sugar content, carotenoid, chlorophyll a, chlorophyll b and total chlorophyll traits. Therefore, the role of additive and non-additive effects was identified in controlling these traits. Protein, proline, chlorophyll a and total chlorophyll traits were more controlled by additive effects, whereas the carotenoid trait was more controlled by non-additive effects and the role of additive and non-additive effects in controlling other traits was almost equal. The KSC704-S7-11 line showed positive and significant general combining ability for most of the studied traits, suggesting this line can be used in breeding programs to improve and increase stress tolerance. In addition, P1 × P3 and P4 × P5 crosses showed the most positive and significant specific combining ability for proline, chlorophyll a, total chlorophyll and carotenoid traits; thus they can be considered as the best hybrids to improve and increase stress tolerance in corn.
Jamal Rahimi Darabad, Varahram Rashidi, Hossein Shahbazi, Mohammad Moghaddam Vahed, Ebrahim Khalilvand,
Volume 7, Issue 2 (3-2021)
Abstract
In order to determine the heritability and genetic parameters of some agronomic traits in barely (Hordeum vulgare L.) cultivars, a seven-parent half diallel (F1 crosses + parents) was conducted in the non-stress and salt stress (8 and 12 ds m-1) conditions in a randomized complete block design with three replications. Genetic analysis was performed by Hayman’s method and Griffing’s fixed model, method 2. The slope of linear regression of Wr on Vr were significantly higher than 0 and had not significant difference with 1 indicating the additive-dominant model was satisfied in all cases. The narrow-sense heritability of traits was medium to high (0.4-0.8) but their broad-sense heritability was estimated relatively high (0.7-0.9). Results of regression graphs showed that Afzal parent had the most dominant allele. The significance of “a” component in most of the studied traits indicated the presence of the additive effects in controlling of traits. The significance of “b” component in most of the studied traits indicated the presence of the dominance effects in controlling of traits. The proportion of positive and negative genes was lower than 0.25 in all of the traits (except for grain weight per spike in 12 ds m-1 salinity), indicating the presence of asymmetry in the distribution of the positive and negative alleles in the parents. Based on general combining ability effects, it was concluded that under salinity, cultivar “Kavir” had favorable alleles in plant height, grain weight per spike and 100 grain weight traits and can be used as a general parent in breeding programs. Estimates of high broad-sense heritability and narrow-sense heritability in most traits indicated that these genetic materials were promising for breeding under normal and salinity stress conditions.
Ali Barzgari, Saeed Malekzade Shafaroudi, Saeed Khavari Khorasani, Farajollah Shahriari Ahmadi,
Volume 8, Issue 2 (3-2022)
Abstract
In breeding programs determination of gene effects and general and specific combining ability for screening of test crosses is necessary. In order to estimate the genetic variance components and the general and specific combining ability of sweet corn lines, an experiment was conducted using 8 sweet corn S6 inbred lines (including 4 maternal and 4 paternal lines) by line × tester mating design in 2019, at the Agricultural and Natural Resources Research and Education Center of Khorasan Razavi Province, Mashhad, Iran. The obtained test cross hybrids were evaluated in a randomized complete block design with 3 replications in 2020. The results of line, tester and line × tester analysis for most of measured traits showed significant differences (p < 0.05). The σ2gca/σ2sca ratio for grain yield was equal to 0.1, showed that while both additive and dominance effects play a role in controlling this trait, but dominance effect was higher. The results for general combining ability of L3 and T1 lines showed positive and significant GCA effect for grain yield. Also, the specific combining ability of grain yield showed that T4 × L2, T1 × L3 and T3 × L1 had the highest SCA rate. In this study, in terms of grain yield, T1 × L3, T4 × L2 and T1 × L4 with 33.96, 30.47 and 27.85 tons per hectare had the highest green ear yield, respectively. These combinations can be as the hybrids with high yield potential in advanced breeding programs for release of new sweet corn varieties.
Ramezanali Pourali, Mohammadhadi Pahlevani, Khalil Zeinalnejad,
Volume 10, Issue 2 (2-2024)
Abstract
Increasing grain yield and improving the quality of bread are among the most important goals of wheat breeding programs in Iran. Understanding the genetic control of traits and finding molecular or morphological markers associated with them are also prerequisites for any genetic engineering program. In this study, 100 progenies of a 10 × 10 diallel cross were used to analyse the genetics of grain yield and bakery values using STS markers associated with HMWG subunits. This research was carried out during 2018 and 2019 cropping season at Gorgan University of Agricultural Sciences and Natural Resources experimental fields. In the first year, 10 wheat cultivars, including Gonbad, Morvarid, Kalate, Ehsan, Sirvan, Baharan, Chamran2, Shush, Mehrgan and Brat collected from different geographical regions of Iran were planted and crossed in the field. In the second year, the parents and crosses were planted in the form of a randomized complete block design with three replications. The grain yield, number of spikes per plant, number of seeds per spike, seed weight, days to emergence and plant height were recorded. The results of this study indicated significant genetic differences between the parents. Narrow-sense heritability analysis revealed that the crossing of cultivars is the best breeding method to enhance seed yield, number of spikes per plant and days to emergence. Also, to improve the number of seeds per spike, seed weight and plant height, classical breeding methods may offer higher efficiency. Marvarid and Gonbad were ranked 1st and 2nd, respectively with respect to general combining abilities for grain yield, attributed to their positive and significant general combining ability effects. The highest specific combining ability was observed for Ehsan×Gonbad, Marvarid×Chamran 2 and Shush×Sirvan crosses. The results of molecular markers analysis showed that the STS markers were able to identify the difference in the baking value of cultivars. The quality score of the cultivars ranged 6 and 10 and to this end, Kalate and Brat were the top cultivars. Therefore, due to superiority in terms of both quantity and quality for yield, these cultivars can be used as parents with desirable genes for future breeding programs. Overall, the STS markers employed in this study proved to be valuable markers for enhancing the genetic background of bread wheat, particularly when employing marker-assisted selection for bakery value.
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