Cereal Research
Year:2015 | Volume:5 | Issue:1|Papers Count:7

Marker assisted selection is one of the important applications molecular markers especially in creation of tolerant genotypes to environmental stresses in crop plants. In this research, seedlings of twenty two rice genotypes were investigated under two culture conditions (normal and drought stress via Manitol) on the basis of completely randomized factorial experiment with three replications at growth chamber of Faculty of Agriculture and Natural Resources, Gonbad Kavous University, Iran, in 2012, and root and shoot length and dry weight were measured. Analysis of variance showed that genotype´culture condition interactions were significant for all measured traits. This result revealed different reaction of the studied genotypes under two culture conditions and genetic diversity among the genotypes in seedling stage. To investigate the molecular diversity among the genotypes, genomic DNA was extracted amplified using 22 microsatellite markers linked to drought tolerance. In total, 106 alleles were detected with the number of 2-7 alleles and the average of 4.28 alleles per locus. The polymorphic information content (PIC) varied from 0.29 to 0.82 with the average of 0.64 and the gene diversity ranged from 0.351 to 0.840 with the average of 0.686. Genetic distance among the studied genotypes was also calculated in the range of 0.23 to 0.99. Cluster analysis using microsatellite data grouped the genotypes in two clusters. Result of principal component analysis showed that the first 10 principal components explained 98.51% of the total variation. Grouping of the genotypes according to first and second principal components assigned the studied genotypes into four groups. Results of these grouping methods demonstrate the suitability of the microsatellite markers to assess the genetic diversity among the rice genotypes. To identify the informative (positive) markers affecting the morphological characteristics, regression analysis was performed. A total of 16 informative markers were detected under both culture conditions which are recommended for drought tolerance in the breeding programs.

To estimate the gene action and heritability of traits related to cooking quality in rice varieties, F2 generations derived from diallel crosses of six rice varieties including Hassani, Shahpasand, Kadous, Vandana, Hashemi and IR36, together with their parents were assessed in a randomized complete block design with three replications in research field of Faculty of Agricultural Sciences, University of Guilan, in 2012. Result of diallel analysis based on the second method of Gardner and Eberhart showed that variety and heterosis effects were significant at 1% probability level for all studied traits indicating additive and dominance variances, respectively. Average heterosis was significant for gelatinization temperature showing significant differences between average parents and hybrids, but was not significant for amylase content and gel consistency. In contrast, specific heterosis was significant for all studied traits. Result of diallel analysis on the basis of third method of Gardner and Eberhart demonstrated that differences among parents and among crosses were significant for all measured traits indicating general and specific combining ability for varieties, while the effect of parents versus crosses (heterosis effect) was not significant for amylase content and gel consistency that confirmed the results of the second method of Gardner and Eberhart. Estimation of Baker ratio showed the higher non-additive than additive effects for amylase content, approximately equal proportion of the additive and non-additive effects for gel consistency and the higher additive than non-additive effects for gelatinization temperature. The graphical analysis of Hayman method showed that all measured traits were affected by partial dominance effects and relatively high narrow-sense heritability indicated higher proportion of additive gene effects for controlling the studied traits. Totally, the results of this research showed that to improve grain cooking quality in the studied population, can firstly be used the additive gene effects via selecting the higher quality genotypes and then the dominance gene effects is utilized by hybridization of the superior genotypes. Furthermore, IR36, Kadous and Shahpasand varieties and Hashemi´Shahpasand, Kadous´Hassani, Hassani´Shahpasand and Kadous´IR36 Crosses had the suitable values for grain cooking quality related traits and are recommended to improve these traits.

To optimize the puddling operation in paddy land preparation, the effects of puddling methods and times on some soil physical properties and grain yield and yield components of rice variety Hashemi were evaluated in this research. The experiments were conducted in a split block design in three replications with two factors, puddling method in four levels (power tiller conventional puddler, power tiller rotary puddler, power tiller cono-puddler and tractor-mounted rotivator) and puddling times in four levels (from once to fourth) in a silty clay soil. Results revealed that the minimum bulk density (0.801 g.cm-3) and maximum penetration depth of falling cone (13.31 cm), weeding efficiency (60.57 %) and puddling index (54.53 %) was related to puddling with tractor-mounted rotivator and the maximum bulk density (0.872 g.cm-3) and the minimum of weeding efficiency and puddling index (51.52 and 44.50 %, respectively) was belonged to power tiller conventional puddler. Increasing of puddling times from once to fourth, decreased the bulk density from 0.882 to 0.795 g.cm-3, but increased the penetration depth of falling cone from 9.04 to 12.39 cm and also weeding efficiency and puddling index from 51.78 to 56.54% and from 45.21 to 51.23 %, respectively. The grain yield in puddling with tractor-mounted rotavator and power tiller rotary puddler (3429 and 3401 kg.ha-1, respectively) were significantly (P<0.01) higher than those of power tiller conventional puddler and power tiller cono-puddler (3346 and 3332 kg.ha-1, respectively). The grain yield increased from 3322 to 3408 kg.ha-1 with the increasing of puddling times from once to fourth, however there were no significant differences between twice, thrice and fourth puddling. In total, results of this research revealed that twice puddling with power tiller rotary puddler or tractor-mounted rotavator can be considered as a proper treatment for puddling operation in silty clay soils similar to experimental site.

The most cultivation area of wheat is in arid and semiarid regions. Therefore, the water requirement of wheat plants in all developmental stages can not be fully provided. In this research, the effects of post anthesis drought stress on grain yield and it’s components, gas exchange and other physiological characteristics of four wheat varieties were assessed. A pot experiment was carried out in factorial experiment based on randomized complete block design with three replications in Campus of Agriculture and Natural Resources, Razi University, Kermanshah, Iran, during 2011 to 2012. The studied factors were including moisture stress in two levels, non-stress and drought-stress at reproductive growth stage (maintenance of soil moisture about 30% of the field capacity from the anthesis to maturity stage) and four wheat genotypes (Pishtaz, DN-11, Sivand and Marvdasht). Results showed that post anthesis drought stress significantly decreased grain yield by decreasing 1000-grain weight. Marvdast and DN-11 genotypes had the lowest grain yield under drought stress. The occurrence of post anthesis drought stress significantly decreased photosynthesis rate, transpiration rate, sub-stomatal CO2 concentration and stomatal conductance, but the photosynthetic water use efficiency wasn’t affected. Also, the leaves senescence led to decrease in the other physiological traits. According to the results of this research, it seems that redusing of the grain yield under post anthesis drought stress was related to decrease in 1000-grain weight due to decreasing of the photosynthetic rate. Also, leaves senescence by decreasing the photosynthetic rate was likely to be more severe than the transpiration rate for reducing of the water use efficiency under drought stress.

To study the effect of seed size on germination indices and seedling growth of four bread wheat varieties, a factorial experiment in randomized complete block design with three replications was carried out in research field of Rice Research Institute of Iran during 2012-2013 and the other factorial experiment based on completely randomized design was conducted in agronomy laboratory of Faculty of Agricultural Sciences, University of Guilan. Treatments in this study consist of four levels of seed diameter (2.25- 2.5 mm, 2.5- 2.75 mm, 2.75- 3 mm and larger than 3 mm) and cultivar (Kohdasht, Moghan 3, Morvarid and native). Results of field showed cultivar and seed size had significant effect on grain yield. Cultivar had not significant effect on emergence rate and seedling cumulative emergence rate, but seed size showed significant effect on this characteristics. The interaction in seedling emergence rate, seedling cumulative emergence rate and grain yield was not significant. Results of experiment showed cultivar had significant effect on all measured characteristics, but had not significant effect on seedling dry weight. Seed size had significant effect on all characteristics, except germination speed, shoot length and root length. The interaction of cultivar and seed size on germination percentage, germination speed, germination energy, shoot length, shoot fresh weight, root fresh weight, seedling fresh weight and shoot dry weight was significant. Maximum and minimum amount of seedling dry weight respectively was 31.37 and 15.54 (mg) that related to seed size larger than 3 mm and seed size 2.25- 2.5 mm. According to results of this experiment seems that wheat seeds with size larger than 3 mm, because of priority in germination and seedling emergence is more suitable for cultivate.

Evaluating of the maize genotypes under different stresses would be useful to identify genotypes with stable and high yield potential. The objective of this study was to estimate yield stability of the grain maize hybrids and identifying high yielding stable hybrids under different water stress conditions in Moghan, Ardabil, Iran. So, seven maize hybrids were assessed by randomized complete block design with three replications under four irrigation conditions including normal irrigation (E1), water deficit at vegetative (E2), water deficit at flowering and (E3) water deficit at grain filling (E4) stages during three years (totally 12 environments). Combined analysis of variance showed that the effects of environments, genotypes and genotype-by-environment (GE) interaction were significant, suggesting that the hybrids responded differently in the studied environment conditions. Therefore, there was the possibility of stability analysis. Results of stability analysis by GGE biplot method revealed that two first and second principal components of the GGE biplot explained 94.7% of the total yield variation. In stability ranking graph of the GGE biplot, SC700, TWC600 and SC724 hybrids were the most stable hybrids, respectively, and the higher grain yield hybrids than the average grain yield were SC704, SC724, SC703, SC720 and SC647 hybrids, respectively. Based on a hypothetical ideal genotype biplot, the hybrid SC704 was better than the other hybrids across environments for grain yield and stability and had the high general adaptation to all environments. Furthermore, the hybrid SC704 at E1, E2 and E4 environments and hybrid SC647 in E3 environment were superior hybrids with the high specific adaptation. Also, comparison of the studied environments showed that the E1 and E4 environments were quite similar in ranking, grouping and assessing stability of the hybrids, whereas the E2 and E3 environments were different from the other environments.

To study the evaluation of grain yield and dry matter remobilization of barley, cultivar Jonoob, under planting pattern and seeding rate treatments, a research was carried out as strip plot in randomized complete block design with 3 replications in Ramin Agriculture and Natural Resources University of Khuzestan, Iran, during 2013-14 cropping season. The experimental treatments were including four planting pattern (flat planting with 17 cm distance of rows, flat planting with 25 cm distance of rows, 3 rows on ridges with 50 cm wide and 2 rows on ridges with 50 cm wide) as first factor and four level of seeding rate (200, 300, 400 and 500 seeds/m2) as second factor. Results showed that the maximum leaf area index, 1000-grain weight, grain yield (5072.1 kg.ha-1) and biological yield (13250.2 kg.ha-1) obtained in flat planting with 17 cm distance of rows. Day to ear emergence, grain number per spike and grain yield decreased by increasing the seeding rate, but the number of spike per m2 increased. The interaction effects of planting pattern and seeding rate were significant on the remobilization efficiency and contribution of the remobilization in grain yield. Three rows on ridge method has more sensitive to changes of the seeding rate, so the contribution of remobilization in grain yield significantly increased with the increasing of each unit in seed rate. This indicates that decreasing of the row spacing together with more utilization of the seeds increased dependence of the grains to storage materials through intensified competition, decrease of the light penetration into the canopy and acceleration of the leaves chlorosis.