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Drought is known as an important factor limiting growth and product of field crops in most parts of the world and Iran. In the present work, the genetic diversity of 100 inbred lines of sunflower was investigated based on agro-morphogical characters with simple lattic design with two replications under normal and drought stress conditions. Combined analysis of variance revealed significant differences among lines for most of studied traits. Uneder normal condition, the highest coefficient of genetic variation was observed for stem diameter and the lowest one observed for relative water content. In drought stress condition, the highest coefficient of genetic variation was observed for seed yield per plant and the lowest one observed for days to flowering. The results of correlation analysis showed that there is significant and positive correlation between seed yield per plant with most of the studied traits in both stress conditions. Stepwise regression analysis revealed that under drought stress condition 73.9 percent of seed yield per plant variation was expailed by heed diameter, leaf width and petiol length and in normal condition 73.6 yield grain per plant variation explained by head diameter and plant height. Cluster analysis grouped lines into 4 clusters in each one of normal and drought conditions but the distruption of lines within groups were differents depending to stress environment that present the genetic variability for drought tolerance in sunflower lines.

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The choice of an efficient breeding procedure depends to a large extent on knowledge of the genetic system controlling the character to be selected. The objective of this study was to determine genetic parameters for yield and other traits including some of the yield components under three planting densities, using analysis of generation means (P1, P2, F1, F2, BC1 and BC2) derived from crosses of B73 with Mo17 and K74/1 inbred lines of corn. Analysis of variance reinforced the hypothesis that interaction of plant density on genera-tion means depends on evaluating genotypes and the kind of trait. Generation mean analysis suggested that both additive and dominance effects were important for most of the traits evaluated in this study, but dominance had a more pronounced effect. Epistasis affected the expression of nine traits in both crosses at three planting densities. Expres-sion of epistasis and genetic parameters differed in the two crosses and were influenced by plant density. Plant densities interacted more strongly with epistasis gene action than with additive or dominance gene action in both crosses.

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The Russian wheat aphid (RWA), Diuraphis noxia (Mordvilko), is a significant insect pest of wheat worldwide. The objective of this study was to assess the genetic variation within and between F2-derived families for reaction to RWA using F3 and F4 families originating from individual F2 plants of a cross between the susceptible line (synthetic hexaploid-11) and the resistance cultivar (‘Halt’). The RWA damage of individual plants within each family was measured using different procedures. Their reaction types were combined into a single data for each individual family (derived from an individual F2 plants) and subjected to statistical analysis. Results indicated that the genetic variation between F2-derived families is greater than within F2-derived families for RWA resis-tance. Broad-sense heritability of RWA resistance, calculated by partitioning phenotypic variation into genetic and environmental components, was 73.2%. A narrow-sense herita-bility estimate of 30% was obtained for the RWA resistance in the ‘Halt’ synthetic hexaploid-11 cross using parent-offspring (F3: F4) regression procedure.

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Inheritance of salinity tolerance was determined in a cross between two spring bread wheat cultivars, "Rovshan" (P1) a tolerant cultivar and "Falat" (P2) a susceptible one. The parents, F1, F2 and backcross generations were studied under salinity conditions (EC= 12 dS m-1) in a greenhouse. Eight characters namely: Heading Date (HD), Plant Height (PH), K+, Na+, K+/Na+ ratio, total Number of Tillers per plant (NT), Ratio of Fertile Tillers per plant (RFT) and total Chlorophyll Content (TC) were recorded to estimate means and variances pooled over replications, according to the weighted generation means analysis method. Generation means analysis of the data revealed that these characters show all types of gene actions (additive, dominance and epistasis) and suggest that complex epistatic effects are important in controlling salt tolerance characteristics. The highest broad sense heritability (0.87) was observed for K+/Na+, indicating the interference of a major gene in control of this trait. Regarding the existence of additive and non-additive effects in controlling traits in this cross, the recurrent selection followed by pedigree breeding may prove useful in improving salinity tolerance in wheat.

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In order to estimate heritability and gene action for grain yield and its related traits in lentil, six basic generations were evaluated in a randomized complete block design with three replications in a field experiment. Besides seed yield per plant, plant height, pod length, and 100-seed weight, the number of pods per plant, primary branches, clusters per plant, nodes per main stem, secondary branches, and the number of seeds per pod were recorded. Generation mean analysis using A, B, C and joint scaling tests indicated that additive [a], dominance [d] and at least one of the epistatic effect (additive×additive [aa], additive×dominance [ad] and dominance×dominance [dd]) were involved in the inheritance of the studied traits. However, simple additive-dominance model was sufficient only for pod length. Significant dominance [d] and dominance×dominance [dd] interactions with opposite sign indicated duplicate epistasis for all traits except pod length. Narrow-sense heritability was low for seed yield per plant, pod length, number of seeds per pod and 100-seed weight and moderate for other traits. Average dominance ratio was more than unity for seed yield per plant, number of primary and secondary branches, pod length, and 100-seed weight, which showed the high importance of dominance gene effect in control of these traits. Due to the presence of greater non-additive gene effects combined with low narrow-sense heritability, selection for almost all of the studied traits in this cross, especially in early generations, would be complex in conventional methods.

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The data set employed in this study was comprised of a number of 6,800 records of lamb’s longevity and their survival rate, collected from 1989 through 2009, from the Lori-Bakhtiari experimental flock at the Shooli Station in Shahrekord, Iran. The data were analyzed using linear models and proportional hazard models with Weibull function. These models included fixed factors and direct additive genetic, maternal additive genetic, maternal common environmental and residual random effects. Genetic parameters were estimated using Restricted Maximum Likelihood (REML) procedure fitting a sire model as well as animal models including different combinations of direct and maternal effects. Estimates of direct heritabilities of longevity and survival rate from different linear models were low (0.01 to 0.09). The maternal heritability ranged from 0.00 to 0.04, and decreaced with increase in the age of lambs. The estimates of heritability in logarithmic scale, original scale and effective heritability obtained from the sire and animal models with Weibull function were medium to high (0.08 to 0.55) and were higher than those estimated through different linear models. The maternal heritability estimated through Weibull models decreased with the age of lambs (0.25 to 0.01). These results indicated that the accuracy of the Estimated Breeding Values (EBV) of lambs’ survival rate from birth up to yearling age, using linear animal models vs. proportional hazard models, would be low vs. medium to high, respectively. Both animal and maternal genetic effects should be considered in the models for improving the survival rate up to 4 months of ages.

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Fennel (Foeniculum vulgare Mill.) benefits from a lot of useful medicinal properties. Iran is known as one of the main producers of fennel. In spite of high medicinal values, fennel’s cultivation is not economically feasible, mainly due to its low yield. It grows wild in different areas in Iran from where diverse ecotypes have evolved. Genetic variance and heritability estimates of traits in a plant’s primary germplasms are needed before planning of a new breeding program. In the present study the genetic diversity and broad sense heritability for 50 fennel ecotypes were assessed under field conditions for a duration of two years. Seed yield, essential oil content and some morphological traits were recorded during a two experimental years. Through stepwise regression, the yield affecting traits and essential oil content were determined. During the first and second experimental years the most effective traits affecting essential oil content were found to be the number of leaves per plant and days to 50% flowering, respectively. The weight of dry biomass affected seed yield the highest during any of the two years and for each separate year. The broad sense heritability during the two experimental years, for essential oil content and seed yield, were 0.46 and 0.63, respectively. However, some such traits as, days to 50% flowering and length of middle internodes showed higher comparative heritability (0.90 and 0.79, respectively). The high heritability of the studied traits in this germplasm indicates the germplasm’s high genetic potential to be made use of in breeding programs.

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In this study, 1973-2003 data of 12,328 animals from Abbasabad Baluchi Sheep Breeding Station, Iran, were used to estimate genetic and phenotypic correlations between Total Weight of lambs Weaned per Ewe Joined in the first, 2^nd, 3^rd and 4^th lambing (TWW1/EJ, TWW2/EJ, TWW3/EJ, and TWW4/EJ, respectively), and TWW of the total four lambing (TWWt/EJ). Also, the study aimed to estimate correlations of TWW1/EJ...TWW4/EJ and Birth Weight (BW) as well as Weaning Weight (WW). The (co)variance components and genetic correlations were estimated by DFREML procedures. Genetic correlation between TWW1/EJ and TWWt/EJ was high and positive (0.76). Genetic correlations of TWW/EJ in different lambing with BW and WW ranged from 0.16 to 0.32 and 0.95 to 0.97, respectively. Repeatability of TWW/EJ for lambing 1-4 was 0.15. Results suggested that selection for increased lifetime reproductive performance could be based on TWW1/EJ in the first lambing. Overall, results indicate that TWW/EJ, as an important but sex-limited trait, may be used in selection criterion to indirectly improve the related traits.