جستجوی مقالات مرتبط با کلیدواژه « عمل ژن » در نشریات گروه « زراعت »

The first step in breeding programs is accurate identification and sufficient knowledge of genetic parameters, including the type of gene action and the heritability of the studied trait. Development of high yielding lines and the identification of heterotic groups are the most important objectives of corn breeders. Also, determining the inbred lines of parents that create suitable hybrids is very valuable and can reduce the duration of the hybrid production program in corn. Graphic diallele analysis is one of the biometric methods of genetic analysis of quantitative and multigenic traits, the results of which can be very useful for improving traits within and between populations as well as producing hybrid varieties. The objective of this experiment was to investigate the genetic control of grain yield and related traits in maize inbred lines. The results of this study can be useful in selecting the most appropriate breeding method for the studied traits and producing high yielding maize hybrids in Zanjan region, Iran.

To estimate the type of gene action, the number of genes, heritability and other genetic parameters controlling grain yield and its related traits in maize inbred lines, a 5×5 diallel crosses design was used. The parents and 20 hybrids derived from their crosses were evaluated in a randomized complete block design with three replications in the research field of Zanjan University, Zanjan province, Iran, in 2019. The studied traits were including plant height, ear length, number of grain rows in ear, number of grains per row, 300-grain weight, and grain yield. The genetic analysis of the data was done according to Hayman (1954) graphical approach.

Estimating the genetic parameters showed both additive and non-additive gene effects in controlling the studied traits in this research. The results of graphical analysis also indicated the existence of over-dominance gene effects in controlling grain yield and its related traits. The alleles increasing the studied traits were of dominant type. Broad-sense heritability varied from 54% for 300-grain weight to 89% for ear length, and narrow-sense heritability ranged from 29% for 300-grain weight to 41% for number of grain rows per ear. Although high general heritability was estimated for most of the studied traits, which indicates the greater role of genetic factors and the relatively less influence of environmental factors in controlling the diversity of these traits, the existence of over-dominance effect of genes and low narrow-sense heritability indicates that the selection of these traits in the early generations will not be successful. Therefore, the breeding methods based on hybridization and selection in advanced generations can be useful in improving and breeding the grain yield and its related traits in the studied maize inbred lines. Also, the use of EP80 inbred line which had the most number of dominant genes for controlling yield and its components may have promising results in improving these traits in breeding programs.

In total, the results of the current study regarding the type of gene action controlling grain yield and its components in the studied maize inbred lines showed the important role of the over-dominance effects of genes. Therefore, the most appropriate strategy for exploiting these genes and improving the population is to obtain hybrid varieties that provide the possibility of exploiting heterosis in the investigated parents. is to use the heterosis phenomenon and produce hybrid varieties.

oilseed rape is one of the most important oilseed plants for supplying required oil and its products. To extent its cultivation area, the introduction of new cultivars with higher genetic diversity is necessary via breeding programs.

To establish of new genetic diversity and evaluation of genetic parameters, the 11 oilseed rape genotypes were crossed in full diallel method; consequently, different traits of parents and their F1 offspring were evaluated in a randomized complete block design replicated thrice.

Analysis of variance revealed that traits including days to flower initiation, physiological maturing, plant height, number of pods per plant, number of grain per pod, thousand-grain weight, and grain yield were significant. The genetic parameters analysis by Griffing's method I model II showed significant GCA, SCA, and REC effects of different traits which represent the evaluated traits were controlled by additive, non-additive, and cytoplasmic gene action effects. Analysis of combining ability represented that among parents, genotype SRL-97-1 had the highest GCA for physiological maturing, number of pod per plant, thousand-grain weight, and grain yield. Also, cross SRL-97-4×SRL-96-20 and SRL-97-15×SRL-97-3had the highest SCA and REC for grain yield, respectively. Besides, the broad sense heritability was higher in traits such as plant height, number of pod per plant and grain yield (H2=0.99); meanwhile, grain yield had a higher narrow sense heritability (h2=0.39).

Consequently, results showed that there was sufficient genetic diversity among evaluated genotypes in which the achieved diversity from the crossing of these genotypes could be applied in cultivar introduction. It is recommended that, genotypes with higher GCA and SCA are suitable for the foundation of a desirable population for selection of promising pure lines with higher yield attributes.

Breeders often use generation means analysis to obtain information about inheritance, gene action, and to determine effective breeding methods to improve important agronomic traits, especially under drought stress conditions. To investigate the genetic parameters of agronomic and morphological traits in durum wheat, a field experiment was carried out using F1, F2, BC1 and BC2 generations obtained from crossing of Shotordandan variety and Dena cultivar under non-stress and terminal drought stress conditions. The experiment was carried out using randomized complete block design with three replications in research field of Islamic Azad University, Ahvaz Branch, Iran in 2016-17 cropping season. To apply terminal drought stress, from anthesis stage, the irrigation of the plots was ceased until physiological maturity. The results of weighted analysis of variance of generations revealed that there was significant differences between the generations for all measured traits except number of grain.spike-1 under non-stress conditions and number of tillers and grain weight.plant-1 in drought stress conditions. The results of generations mean analysis for spike length under non-stress conditions and plant height and spike length under stress conditions showed that the three-parameters model had the best fit. However, for other measured traits, significant chi square test (χ2) indicated the presence of non-allelic interactions in the inheritance. Additive and dominance effect played roles in controlling most of the studied traits, but the effect of dominance component was greater than the additive component. Broad and narrow sense heritability of traits under non-stress conditions varied from 11-84% and from 1-75%, respectively, and under stress conditions from 24-70% and from 1-40%, respectively. Considering the greater role of genes with non-additive effect in controlling most of traits, except plant height, spike length and 1000-grain weight, selection in durum wheat advanced breeding generations, when breeding lines are fixed and relative purity achived, is suggested.

By progeny trial after a diallel crossing, the function of genes and inheritance of quantitative traits can be estimated. This increases the ability to select parental lines, to participate in crosses, and determines the management of generations in the segregating populations.

In order to understand the genetic structure of grain yield and yield components, seven bread wheat cultivars including Bolani, Falat, Mehrgan, Meraj, Kalateh, Frontana and MV17 were planted in the crossing block and direct crosses were performed among the seven cultivars to produce F1 generation. The progenies of the crosses with their parents were evaluated based on a randomized complete block design (RCBD) with three replications in Gorgan agricultural research station in 2020-2021 cropping season.

The results of this experiment showed a significant difference among the genotyps in all the studied traits. Estimation of genetic parameters using Heiman's method showed that the values of dominance variance were significantly greater than the additive variance in grain yield, biological yield, 100-kernel weight, number of grains per spike, grain weight per spike and peduncle length. There was a small difference between the values of dominance and additive variance in the plant height and days to anthesis. In biological yield, 100-kernel weight and days to anthesis, the proportion of dominant alleles and was greater than the recessive alleles in parents, while the proportion of dominant and recessive alleles was equal in the other traits. High broad-sense heritability in grain yield (89%) and biological yield (93%) and grain weight per spike (74%) and their low narrow-sense heritability (10%, 10% and 13, respectively) showed a greater share of the dominance effect in controlling these traits. The results of graphical analysis showed that grain yield, biological yield and 100-kernel weight were controlled with dominance gene action and number of grains per spike, peduncle length and plant height were controlled with incomplete dominance gene action. The distribution of parents around the regression line showed that Falat and Mehregan cultivars carried the most dominant genes and MV17 and Frontana cultivars carried the most recessive genes in controlling grain yield and biological yield.

The results of this study indicated that due to the greater share of non-additive effects of genes in grain yield, biological yield and yield components, it is better to select among the progenies of the crosses be postponed to more advanced generations. While, genetic improvement in plant height and days to anthesis can be achieved in the early generations.

Maize (Zea mays L.) is the fourth most important cereal after wheat, barley and rice in Iran (Ahmadi et al., 2018). Given the future demand of corn as a food for humans and as a feed for livestock, there is a continuous need to evolve new hybrids with high yield. To achieve this, combining ability study is one of the best options (Reddy Yerva et al., 2016). Griffing diallel method (Griffing, 1956a;b) is one of the methods that examines how genetic control of traits in parents. It also evaluates the general and specific combining ability of parents and hybrids. The purpose of this study was to estimate the general and specific combining ability of parents and hybrids.

In order to estimate the gene action and heritability of important agronomic traits, five S7 maize lines were crossed in a 5×5 half-diallel and F1 hybrids derived from them were cultivated in a randomized complete block design with three replications at the Research Farm of Graduate University of Advanced Technology, Kerman, Iran in 2017. Number of ear, grain number per row, grain row number, grain number per ear, ear length, 100-grain weight and grain yield per square meter were evaluated. Analysis of data for general and specific combining ability was carried out following Griffing (1956) method IV model I using DIALLEL-SAS05 program (Zhang et al., 2005).

Analysis of variance showed that there was a significant difference between genotypes for all studied traits that showed the role of additive and non- additive effects in controlling these traits. The low ratio of GCA variance to SCA for the grain row number and number of ear traits, and in other words, the lack of significant GCA variance of these traits showed that genetic control of these traits has a non-additive effect. General (GCA) and specific (SCA) combining ability variances for grain number per row, grain number per ear, ear length, 100-grain weight and grain yield per square meter were significant at 1% probability level, indicating the control of these traits by additive and non-additive effects of genes with a greater proportion of additive gene effects.

The results of this study showed that although genes with both additive and non-additive effects played a role in controlling of yield and its component traits. In controlling traits of ear number and rows, the role of non-additive effects was greater. Whereas, other traits were more controlled by the additive gene effects. The Line14 had positive and significant GCA for the yield trait and most of its related traits, which indicated that the line could be used in breeding programs to improve yield and increase it. The results also showed that the P1 × P2 and P3 × P5 crosses had positive and significant SCA for yield and its related traits, so these hybrids might be the best for improving and increasing maize grain yield.

Using an appropriate breeding method for genetic improvement of quantitative traits mainly depends on the nature of gene action and heritablity. In order to estimate genetic parameters for agro-physiological traits in rapeseed, a generation mean analysis was counducted using the following three crosses; Opera×Dalgan (C1), Parade×Dalgan (C2) and Licord×RGS003 (C3). The parents, F1, F2 and BC1, BC2, RF1, RF2, RBC1, and RBC2 generations were studied for 13 traits. The parents and segregating populations cultivated under drought stress in a randomized complete block design with three replications at Dryland Agricultural Research Institute, Sararood, during 2016-2017 croping season. The results showed significant differences among ten generations for all traits including days to maturity (DM), plant height (PH), silique per plant, silique length (SL), seed per silique, 1000-seed weight, leaf water content, chlorophyll content, electrolyte leakage, leaf temperature, plant yield, seed oil content (SOC) and harvest index in three crosses, indicating genetic differences between the parental genotypes. The highest level of best- and mid-parent heterosis was observed in F1 (229 and 300%, respectively) and RF1 (255 and 322%, respectively) generations for plant yield in C3. In addition to the additive-dominance model, mean generation analysis and joint scale test showed that epistatic effects are important for all the traits except silique length. The broad- and narrow-sense heritability of the traits in the crosses ranged from 0.26 to 0.98 and from 0.08 to 0.67, respectively. This study revealed that dominance variance has the most important genetic effect in controlling of all the studied traits except for DM and SL in three crosses, PH in C1 and C2, and SOC in C2 and C3.

Maize (Zea mays L.) is considered as one of the most important cereals in the field of world production. Water stress due to water shortages and its various forms is one of the main and most common limiting factors of crop yield, especially in arid and semi-arid regions of the world. Therefore, in corn, identification, selection and use of tolerant cultivars against drought stress in order to prevent the reduction of crop yield is considered as one of the most important and essential issues in breeding programs. Breeding of high-yield and good quality cultivars is one of the main goals of the breeding program which requires comprehensive information about the genetic structure of the parents, as well as their general and specific combining ability, the level of heterosis, genes action, and their interaction with each other and the environment. Therefore, the present study was conducted to evaluate the gene effects, heritability and the control of yield and its components in drought stress conditions compared to normal conditions in corn. In order to select suitable breeding methods and take an effective step in the production of high yielding maize cultivars.

In order to estimate the gene action and heritability of important agronomic traits, five S7 maize lines in a 5×5 half-diallel cross with F1 hybrids derived from them in a randomized complete block design with two replications in two normal conditions (irrigation intervals of 5 days) and drought stress (8 days irrigation) were cultivated at the Research Farm of Graduate University of Advanced Technology, Kerman, Iran in 2017. Number of ear, grain number per row, grain row number, grain number per ear, ear length, 100-grain weight and grain yield per plant were evaluated in two conditions. The data were analyzed by analysis of variance and regarding the significance of the variance of treatments, the analysis was performed using Griffing's second method. In order to carry out the diallel analyzes by Griffing's second method in two normal and drought stress conditions and combined analysis of variance was used SAS command.

Combined analysis of variance showed that there was a significant difference between genotypes, environment and genotype×environment interaction for all studied traits, indicating the genetic differences between lines and corn hybrids. The results of combined variance analysis showed a significant interaction effects between general and specific combining ability with the environment, which indicates the different of inheritance of traits in each environment. The results of diallel analysis by second Griffing method under normal conditions indicated that the grain number per row, grain row number, grain number per ear and ear length more controlled by non-additive effects of genes, while these traits more controlled by additive effects of genes under water scarcity conditions.

The results of this study showed that although genes with both additive and non-additive effects played a role in controlling the traits, the contribution of each of these effects was different in controlling each of the traits. Also, the control of these traits was different in both normal and drought stress conditions, and the genes controlling these traits differed from environment to environment. The KSC704-S7-7 line showed positive and significant general combining ability for grain yield and most related traits in both conditions which can be used in breeding programs to improve grain yield and increase it. In addition, the P2×P4 cross under water scarcity conditions and the P1×P3 cross under normal conditions, which showed positive and significant specific combining ability for grain yield and most related traits, are introduced as the best hybrids for improvement and increase of maize grain yield for water scarcity and normal conditions, respectively.

Take-all disease, caused by Gaeumannomyces graminis var. tritici (Ggt) is one of the most important of wheat diseases that causes severe damage to crown and root rot in different regions of Iran. Development of resistant varieties requires genetic study on inheritance and type of gene action in disease resistance, which so far has not been any report in relation to (Ggt). Therefore, in order to genetically analyze of resistance to this disease, the generations of P1, P2, F1, F2, BC1 and BC2 were produced and planted at greenhouse. After artificial infection of plants with T-41 strain of (Ggt), the phenotypic measurement was based on the degree of disease damage and its symptoms on the crown and root were recorded. The results of the generation mean analysis indicated that the five-parameter model can explain the variations between the means of generations in two crosses (1528×164 and 1622×1526) and four parametric models in third cross(1528×1546). Additive, dominance and epistatic effects including additive × dominance and dominance × dominance were exist in controlling of this trait. The dominance and epistatic effects were greater than the others. Distribution of F2 generations, showed a tendency toward susceptibility so the susceptibility was dominant to resistance. Analysis of the F2 data based on the classical ratios showed that with phenotypic grouping of F2 generation in three susceptible, semi-susceptible and resistant groups. These three groups corresponded to the epistatic ratio (9:6:1), respectively. This result was almost consistent with the results obtained from the Generation means analysis, since in GMA, duplicate dominant epitasis and partial duplicate interaction were detected and the minimum number of genes involved in controlling this trait has been estimated by 2 gene that it has a relative accordance by duplicate dominant interaction with additive effect (9:6:1).

In order to study the type of action of genes and inheritance of traits in chickpea, the generation mean analysis was accomplished using the cross of six cultivars of chickpea called Pirouz, Bivanich, Flip51-87c, Iccv2, Kaka, and Azad. Parent seeds along with seeds of F1, F2, BC1, and BC2 were cultivated in a randomized complete block design with three replications, and eight traits including plant height, number of seeds per plant, number of pods per plant, number of hollow pods per plant, number of double-grain pods per plant, 100-seed weight, number of days to 50% flowering, and grain yield were evaluated. The variance analysis results indicated that the mean squares of generations were significant for all the traits, so the generation mean analysis for the studied traits was performed. Based on the results of generation mean analysis for all the studied traits besides the additive and dominant effects, epistatic effects were also fitted which indicates the complexity of the inheritance of these traits. The results also showed that the plant height was controlled by incremental and dominating effects. It was also determined that the dominant genetic effect has the most significant role in the inheritance of most of the studied traits.

Introduction Maize (Zea mays L.) is considered as one of the most important cereals in the field of world production. Water stress due to water shortages and its various forms is one of the main and most common limiting factors of crop yield, especially in arid and semi-arid regions of the world. Therefore, in corn, identification, selection and use of tolerant cultivars against drought stress in order to prevent the reduction of crop yield is considered as one of the most important and essential issues in breeding programs. In order to design and implement an effective and useful program, knowledge of the genetic control of the studied traits is essential the impact of environmental factors and the interaction between genetic and environmental factors. Among different methods of genetic analysis of quantitative traits, diallel analysis using Hayman method as an appropriate and efficient method for estimating the genetic structure of the populations in the relatively short time was considered by plant breeders. Therefore, the present study was conducted to evaluate the gene effects, heritability and the control of yield and its components in drought stress conditions compared to normal conditions in corn. In order to select suitable breeding methods and take an effective step in the production of high yielding maize cultivars. Materials and methods In order to estimate the gene action and heritability of important agronomic traits, five S7 maize lines in a 5×5 half-diallel cross with F1 hybrids derived from them in a randomized complete block design with two replications in two normal conditions (irrigation intervals of 5 days) and drought stress (10 days irrigation) were cultivated at the Research Farm of Graduate University of Advanced Technology, Kerman, Iran in 2017. Number of ear, grain number per row, grain row number, grain number per ear, ear length, 100-grain weight and grain yield per plant were evaluated in two conditions. The graphical analysis was carried out using the Hayman method and genetic parameters including additive variance (D), non-additive variance (H1 and H2) and covariance of additive with dominance effects (F) were also estimated by Hayman's proposed regression method. In order to carry out the diallel analyzes by Hayman method in two normal and drought stress conditions and combined analysis of variance was used SAS command. Results and discussion Combined analysis of variance showed that there was a significant difference between genotypes, environment and genotype×environment interaction for all studied traits, indicating the genetic differences between lines and corn hybrids. The simple effect of a for all traits, except for the number of ear and its interaction with the environment, was significant for all traits except number of ear, grain number per row and grain yield per plant which showed that additive effects play a role in controlling these traits and showed a different behavior in the two environments. The simple component b, which includes non-additive effects, was significant for all traits, and its interaction with the environment was also significant for all traits. The significance of the interaction between a and b effects with the environment indicates the difference in the type of additive and non-additive genes in both normal and drought stress conditions. Generally, the gene type for controlling traits and their gene action, potential of dominance and recessive genes in parents, and additive and dominance effects were different for most studied traits of this research in both normal and drought stress conditions. The graphical results of Hayman's analysis showed the role of over-dominance genes effects in controlling most traits in normal and drought stress conditions. Conclusions The results of this study showed that although genes with both additive and non-additive effects played a role in controlling the traits, the contribution of each of these effects was different in controlling each of the traits. Also, the control of these traits was different in both normal and drought stress conditions, and the genes controlling these traits differed from environment to environment. The results of narrow sense heritability and Hayman graphic analysis of traits showed that these traits were controlled by the non-additive gene effects. Therefore, it can be said that in order to breed and improve the genetic value of the population for these traits (yield and its components), the selection method will not be very successful, but it should use the phenomenon of heterosis and crossed the parents to produce hybrids.

Study of heritability and gene action to improve agronomic and physiological traits, especially under drought stress conditions, are very important. The objectives of this study were to investigate heritability for important agronomic traits and some physiological characters in a cross between two spring wheat cultivars. The experiment was carried out using different generations (BC1, BC2, F3, RF3) derived from crosses between two cultivars, Arg (tolerant to salinity and drought) and Moghan3, under drought stress conditions using randomized complete block design with two replications in 2014 cropping season at the University of Tabriz research station, Iran. In all plots, irrigation was withheld after antesis until the end of season. Generation mean and generation variance analyses were used to estimate gene action and genetic variance components, respectively, for agronomic and physiological traits of wheat under water deficit conditions. Based on the analysis of variance, significant differences were observed between generations for peduncle length, spike length, flag leaf width, flag leaf area, number of fertile tillers, leaf chlorophyll content, days to heading, spike weight, straw weight, biomass, grain yield and harvest index which revealed the presence of genetic differences between two parents. The generation mean analysis for the flag leaf width and flag leaf area showed that the three-parameter model was the best fit. However, for other traits chi-square of the three parameter model was significant, indicating the presence of non-allelic interactions in the inheritance of these traits. Although both types of additive and dominance effects were significant in control of the studied traits, but dominance component was larger than the additive effect. The dominance × dominance epistasis was also more important than other epistasis components for the studied traits. The broad-sense and narrow-sense heritability of the traits ranged from 0.754 to 0.941 and from 0.144 to 0.579, respectively. Estimates of variance components revealed that dominance variance was greater than additive variance for peduncle length, spike weight, straw weight, biomass, grain yield and harvest index. While, the additive genetic variance was higher than the dominance genetic variance for spike length, flag leaf width, flag leaf area, fertile tiller number, chlorophyll content and days to heading. The average degree of dominance was more than one for all of the traits which indicated the presence of over-dominance gene action in controlling these traits. Presence of non-additive genetic effects in controlling the traits showed the necessity of selection in advanced segregating generations, when populations are relatively fixed line, using bulk-pedigree method or for development of hybrid varieties in wheat, should the pollination and male sterility barriers will be overcome.

To estimate gene action and heritability of yield and yield components of maize, F2 progenies derived from half-diallel cross of five S7 maize lines along with parental lines were assessed in a randomized complete block design with three replications at the Research Farm of Graduate University of Advanced Technology, Kerman, Iran, in 2017-18. The studied traits were grain yield and its components including number of ear per plant, number of grain per ear, number of grain row, number of grain per row, ear length and 100-grain weight. Results of analysis of variance showed significant differences among genotypes for all studied traits at 1% probability level. The results of Hayman’s graphical analysis also indicated that the contribution of non-additive gene effects was more important than additive effects in controlling most traits. Number of ear, number of grain per row and grain yield per plant were controlled by the incomplete dominance effects of genes, while the other traits were controlled by over-dominance effects. Broad sence heritability of the traits varied from 0.03 for number of grain row to 0.50 for 100-grain weight. The results of this study showed that both hybrid production and selection methods can be used to breed the number of ear, number of grain per row and grain yield per plant, but to breed the other traits in the studied population, the use of heterosis phenomenon and hybrid production is suggested.

In order to estimate the effects of general (GCA) and specific (SCA) combining ability, heterosis and genetic control of different traits in rapeseed including yield and seed oil content, six lines of spring type and three testers Opera, Parade and Licord of winter type were crossed in 2014-2015. The 18 progenies and their parents were evaluated in a randomized complete block design at the Dryland Agricultural Research Institute (Sararood) under water-stressed (WS) and well-watered (WW) conditions in 2015-2016 cropping season.The results of line × tester analysis revealed that the GCA due to lines in all traits except for pod length in WW and the SCA due to line × tester in all of the traits except for seeds per pod and oil content in WS, and pod length in WW were significant for both environments.The genetic control of the traits was different in both conditions indicating that the gene effects were influenced by the environment for most studied traits. For seed yield, additive and non-additive effects were more important in WS and WW environments, respectively. Seed oil content had relatively low narrow sence heritability in both conditions. The most heterosis for seed yield was belonged to Comet × Opera (168%, WS) and Amica × Licord (171%, WW) hybrids The highest heterosis for seed oil content was observed in Shiralee × Opera hybrid in both environments (12.6% in WS and 6.4% in WW). The testers Opera and Licord were suitable to improve yield in WS and WW environments, respectively. The lines Comet and Dalgan had the highest GCA and the Dalgan × Licord hybrid had the highest SCA (Top cross) for seed yield in both conditions.

Drought is the main abiotic stress seriously influencing wheat production and quality in Iran. Information about genetic controlling drought tolerance inheritance is necessary to determine the type of breeding program as well as develop tolerant cultivars. In this study, Bayesian inference using LASSO method used to identify the most important gene effects related to drought tolerance in context generation mean analysis. For this purpose, field experiments consist of two pairs of crosses with non-tolerant and tolerant cultivars and generations derived from them were carried out across two years as split plot designs based on RCBD with three replications in which main plots assigned to irrigation treatment consist of two levels (well watered and cessation of irrigation at pollination stage) and sub-plots given to the generations. Bayesian inference is an alternative approach which combines available prior knowledge (prior distribution) with the information contained in the data. The result is the posterior distribution containing all information to interpret genetic structure. LASSO is an effective method to apply shrinkage and selection on model variables. Non-important effects in the model shrunk toward zero and excluded from the model. While for important effects, less shrinkage will be achieved. Since the additive, dominance and epistatic gene actions involved in drought tolerance inheritance, methods which utilize all type of gene effects, like recurrent selection followed by pedigree method may be useful for drought tolerance stress improvement.

To estimate combining ability and genetic parameters for some agronomic and physiologic characteristics, a reciprocal diallel experiment was conducted with nine rapeseed (Brassica napus L.) varieties. Parents and their F1's were sown in drought stress (S) and non-stress (NS) environments using 9 × 9 lattice design with two replications at the Dryland Agricultural Research Institute, Sararood, Kermanshah, in 2015-2016 cropping season. Results showed that effect of general and specific combining ability (GCA and SCA), and reciprocal crosses (REC) were significant (P < 0.01) for most traits in both environments. Parents Shiralee for seed oil content (SOC), Comet and Dalgan for seed yield (SY) were the best general combiners while cross RGS003 × Licord was the best specific combination for thousand seed weight (TSW), relative water content (RWC), SOC, and SY in both environments. Additive genetic variance was more important component for days to flowering, plant height, silique length, TSW and SOC in both environments, while dominance gene effect was greater than the additive component for SY (both environments), number of siliques/plant (NSP), RWC and leaf temperature (S) and electrolyte leakage (NS). According to the results of the graphical analysis, the gene action for most traits was partial dominance, while it was over-dominance for NSP (S), RWC and SY (NS). Maximum and minimum of narrow-sense heritability were obtained for TSW (0.92, in S) and RWC (0.21, in NS), respectively. This study showed that it is possible to improve SY, SOC and other agronomic and physiologic traits through crossing between different varieties of rapeseed for both conditions.

In order to graphical analysis and estimation of genetic parameters for yield and its components, a one-way diallel cross was applied with seven bread wheat genotypes. In this study, 21 hybrids along with their parents were evaluated in a randomized complete block design with three replications. The results of variance analysis showed significant difference among genotypes for plant height, peduncle length, spike length, the number of seeds per plant, plant grain yield, and 1000-grain weight. The results of Jinks and Hayman primary test showed that assumptions for the number of seed per plants and plan grain yield were authentic, but it was true for spike length, peduncle length, and 1000-grain weight after eliminating one parent and for plant height by eliminating two parents. The results of Hayman analysis showed the role of additive and non-additive effects of genes on the control of traits. Maximum and minimum of narrow-sense heritability were obtained for plant height (0.47) and the number of seeds per plant (0.21), respectively. According to the average degree of dominance and the results of the graphical analysis, the gene action for grain yield and plant height was additive effects, while it was over-dominance for peduncle length, the number of seeds per plant, spike length and 1000-grain weight.

Drought is one of the main dangers for optimum production of wheat. Achieving optimal results in breeding programs require to make informed choices of parents based on general and specific combining ability.In order to study the genetic characteristics, general and specific combining abilities and gene actions under drought stress conditions, a half diallel cross including 9 varieties of wheat was used. Seeds of parents and F2 hybrids were planted based on a randomized complete block design with three replicates in Shahid Bahonar University in autumn of 1392. Parents and F2 progenies were compared in a number of agronomic traits such as plant height,days to maturity,spike length,peduncle length,seed weight,flag leaf area and grain yield. Diallel results based on method 2 of Griffing B model and Hayman _ Jinks showed that general combining ability was significant for seed weight, plant height, days to maturity, peduncle length in statistical level of 1% and for the other traits at 5% statistical level and specific combining ability was significant for seed weight, plant height and grain yield in statistical level of 1% and for the other traits at 5% statistical level.The ratio of mean square of gca to sca was significant for all traits except of grain yield.Therefore, in grain yield most genetic variation is belonged to non-additive genetic variances. The broad and narrow sense heritabilities for the studied traits had ranged from 55 to 74 and from 32 to 61 percent, respectively. The Hayman _ Jinks graphical analysis showed plant height, days to maturity and grain yield controlling by over dominance gene actions however the other traits was controlled by relative dominance gene actions.

Salinity stress is one of the serious threats for high productivity of crops, especially in wheat as a key staple food for world population. Understandingthe inheritance of yield and yield components is very important in wheat breeding programs for salinity tolerance. In this research, to evaluatethe gene action of yield and yield components, seven Iranian wheat cultivars including Falat, Bam, Ghods, Roshan, Arg, Kavir and Pishtaz along with their crosses were cultivated in randomized complete block design with three replications under both normal and salinity stress conditions at National Salinity Research Center,Yazd province, Iran,in 2014. All initial assumptions for the traits were indefeasible, therefore combined analysis of variance was done based on Jinks-Hayman approach. The results of analysis of variance showed that all traits including grain yield, biological yield, tiller number, peduncle length, plant height and 100 grain weight had significantly simple additive effect “a” and “a × environment”interaction effect. Also, the simple effect of b3 which is equal to specific combining ability in method 1 diallel analysis, and its interaction with environment were significant for all studied traits. Significant “a” and “b3” terms indicated the important role of additive and dominance effects in the inheritance of trait in both conditions. In this research, the cultivar Roshan had the best combining ability for yield, biomass and tiller number. Generally, the gene type for controlling traits, gene action, potential of dominance and recessive genes in parents,maternal effects and additive and dominance effects were different under twoenvironmental conditions, non-stress and salinity stress. Estimated high broad sense and moderate to high narrow sense heritabilities indicated that thestudied genetic materials could be promisingly used to improve these traits under non-stressconditions aa well as salinitytolerance.Therefore, it ispossibleto select tolerant genotypes to salinity stress in Iranian bread wheat cultivars used in this research.

Grain yield is the result of interaction among its components. This trait is influenced by genetic and environmental factors. Therefore, yield improvement through plant breeding, especially in early generations is difficult. Selection can be effective if it did base on yield components. In order to study mode of genes action and heritability of grain yield and some of its related traits in bread wheat, generations of cross Gasspard × DN-11 including F1, F2, BC1 and BC2 along with parents (P1and P2) were studied in the research field of Tehran Agricultural and Natural Resources, in a randomized complete block design with three replications. The results of the Generation Mean Analysis showed that in most cases, a digenic model including additive, dominance, and epistasis effects was appropriate to explain the variation of generations mean, so that the six parameters model including mean (m), additive (d), dominance (h), and epistasis additive × additive (i), additive × dominance (j), and dominance × dominance (l) were effective in controlling of traits under study. The epistasis effects including additive × additive, dominance × dominance were distinguished as the most important effects in controlling plant height, number of grain per spikelet, number of sterile spikelets, and grain yield, as well as additive and dominant effects of genes for 1000-grains weight and grain weight per spike, and also the epistasis effects of additive × dominance, and dominance × dominance for traits including spike length, peduncle length, and days to flowering. Thus, it should be considerate the mode of gene action for population improvement, as well as choosing an appropriate breeding method.