IRANIAN JOURNAL OF DRYLAND AGRICULTURE
Year:2016 | Volume:5 | Issue:1|Papers Count:7

Water deficit always has been considered as one of the most limiting factor to agricultural production in Iran, as the country is located in the arid and semi-arid zone. This study aimed to evaluate genetic variation among wheat germplasm for drought tolerance and to determine the possible application of 13C isotope discrimination method in identifying wheat genotypes with higher WUE. A number of 160 wheat lines and cultivars with varying level of drought tolerance were examined in observation plots under augmented randomized complete block design along with 4 check cultivars repeated in all 10 blocks. The experiment was performed at Dryland Agricultural Research Station in Maragheh under rainfed conditions during 2009-10 growing season. Data analysis revealed significant differences among the evaluated genotypes for yield under dryland conditions. Our finding suggested that late-mature genotypes have shorter height and lower harvest index, lower thousand kernel weight, which resulted in less yield under dryland conditions. The findings lead to the identification of 22 superior lines with higher yield and desired agronomic traits compared to the check cultivars. Calculation of linear correlation showed significant negative correlation between D and wheat grain yield. Under dryland conditions, genotypes with higher yield had lower 13C isotope discrimination. Grain yield showed a significant and negative correlation with 13C discrimination in wheat grown under dryland conditions. This finding suggest that using 13C discrimination to identify wheat genotypes with higher WUE will be able to yield more under dryland conditions.

In order to study the effect of drought stress and seed size on seedling characteristics of chickpea genotypes, a factorial experiment based on completely randomized design with three replications carried out under controlled conditions. The treatments were three factors (i.e. genotype, seed size and drought levels). Four chickpea genotypes (Arman, Azad, ILC 482 and a landrace from Turkey) were as factor A, and three seed sizes (large seeds with>8 mm, medium seeds with 6-8 mm and small seeds with less than 6 mm in diameters) were as factor B and drought stress levels (induced by PEG 6000) were in five levels (0, -0.2, -0.4, -0.6 and -0.8 bar) as factor C. Drought tolerance in the seedlings was evaluated by using of traits ranking method.Results showed that seedlings grown from small seeds had the highest germination rate, shoot and root lengths, seed vigor index; where as seedlings grown from large seeds produced the highest seedling fresh and dry biomasses. In conclusion, ILC 482 genotype was tolerant to drought stress based on traits ranking method. The seedlings grown from large seeds were more susceptible to drought stress compared with seedlings grown from medium and small size seeds.

Wheat production has been challenging with drought stress in the most parts of Iran. In drought prone environments, the first strategy is breeding for higher grain yield. Grain yield is strongly affect with genotype by environment interaction, whereas this interaction is comparatively small for the secondary traits. In this research, genetic control of drought related secondary traits such as leaf-rolling were evaluated using 9×9 diallel analysis in a randomized complete block design with three replications in Shahid Bahonar University of Kerman research field. Low Baker ratio (0.25) and narrow sense heritability (0.20) showed the central role of nonadditive effects on genetic control of leaf-rolling. Hence, bulk, single seed decent, and double haploid procedures are proposedfor breeding this trait. Moreover, flag leaf length, peduncle length and plant height had high narrow sense heritability (0.65, 0.56 and 0.51, respectively) and Baker ratio (0.67, 0.65 and 0.46, respectively). These results showed that pedigree and back cross methods are appropriate for breeding these traits. Total tiller number (22%), peduncle length (19%), flag leaf width (15%) and plant height (14%) had the highest response to selection. This is because of either high phenotypic variability or narrow sense heritability of these traits.

Low phosphorus (P) availability and its absorption limits barley production and quality in calcareous soils, especially in rainfed areas. With the aim of evaluation of genotypic variation for P absorption and accumulation in shoot and seed, and its influences on grain yield affecting morpho-physiological traits, 100 barley genotypes (including local landraces, advanced lines and released varieties) were studied under rainfed conditions. The experiment was conducted in square lattice. Based on ANOVA, there was significant differences among genotypes for shoot and seed phosphorus concentration and content, as well as for all measured morpho-physiological traits. The high range of variation for the measured traits showed that there was a great genotypic variation among barley genotypes for the measured traits. Shoot phosphorus concentration and content had significant and positive correlation with seed phosphorus concentration and content. On the other hand, seed phosphorus content had positive correlation with grain yield and thousands kernel weight. In short, the result of this study revealed great genotypic variation for the phosphorus absorption among barely genotypes. In addition, efficient genotypes had greater ability to absorb and accumulate more phosphorus that leads to increased grain yield with phosphorus dense seeds under drought conditions.

In order to study the effects of nitrogen on grain yield of rainfed wheat, nitrogen agronomic efficiency (NAE) and rainfall use efficiency (RUE), two field experiments under different moisture conditions (rainfed and supplemental irrigation) were conducted in Kurdistan province in 2012-2014 growing seasons. The treatments comprised of five nitrogen rates (0, 30, 60, 90 and 120 kgha-1) as subplots, and three nitrogen application times as main plots (total in the fall, 2.3 in the fall+1.3 in the spring, and 2.3 in the fall+1.3 in the spring) with three replications as split-plot design in randomized complete block design. Under rainfed moisture conditions, application of 30, 60, 90 and 120 kg N.ha-1 significantly increased grain yield 478, 961, 1086 and 850 kg.ha-1, respectively. By increasing nitrogen application, WUE was increased significantly (p<0.05) and then reached to maximum (10.3 kg.mm-1.ha-1) in N90. Under supplemental irrigation at the heading and two weeks after heading stages, application of 30, 60, 90 and 120 kg N.ha-1 significantly increased grain yield 849, 1357, 1540 and 1790 kg.ha-1, respectively. Also, N90 treatment had the highest grain yield, NAE and RUE. Meanwhile, N60 application either total in the fall or splitting had the same effects on grain yield, grain protein content and NAE and RUE.

This research conducted to investigate on effects of foliar spraying and soil split application of nitrogen on differences of dryland bread wheat varieties and genotype for nitrogen uptake, grain and straw yield. In order to do this study, experiment was conducted with factorial arrangement completely randomized block design with factor A: total, split and foliar spray applications and factor B: wheat varieties Azar2, Sardari and, Turkey 3702 genotype with three replications for three years from 2007 to 2010 in Maragheh. The results indicated that effects of urea foliar spraying, split and total nitrogen fertilizer application methods were significantly different for grain and straw yields, nitrogen uptake grain and straw of wheat varieties and genotype. Urea spraying and split method of nitrogen had highest grain and straw yields and nitrogen uptake. In addition, main effects of wheat varieties and genotype were found significantly different. Azar2 and Turkey 3702 genotype at same level increased grain yield compared to Sardari variety. Turkey 3702, Azar2 and Sardari at different methods of nitrogen application were significantly different for nitrogen content of grain. Turkey 3702 compared to other wheat varieties had heights grain nitrogen content at nitrogen split application. It can be concluded that spray and split applications of nitrogen compared to total nitrogen application can increase nitrogen content of grain and grain and straw yields. In addition, wheat genotype and varieties at nitrogen application methods can increase differently nitrogen uptake, grain and straw yields.

In order to estimate genetic components of variance for agronomic traits in sunflower, 16 single cross hybrids (obtained by crossing between four restorer lines with four CMS lines) were evaluated in RCBD with three replications under optimum and water limited conditions. The data were analyzed as Line×Tester mating design. Results showed that under optimum irrigation conditions, growth period, seed weight and oil content were under control of additive geneeffect, whereas plant height was under control of non-additive gene effect. Date of flowering, head diameter, seed and oil yield were under control of both additive and non-additive gene effects.Under water limited conditions, date of flowering was under control of additive, whereas plant height, seed and oil yield were under control of non-additive gene effects. In water limited conditions, the values for heritability were lower than optimum conditions. This difference might be due to drought stress. The results indicated that selection based methods may be efficient for production of early mature sunflower hybrids under drought conditions, whereas hybridization is needed for improvement of plant height, seed and oil yield. Screening of genetic materials under limited water supply could improve efficiency of breeding programs for providing of drought tolerant cultivars.