Crop Production
Year:2010 | Volume:2 | Issue:4|Papers Count:10

In order to evaluate the relationships between some traits of Iranian rice seedlings under saline conditions,, 75 Iranian cultivars as traditional, improved and introduced cultivars were used, as a randomized complete block design experiment with 3 replications at Rice Research Institute of Iran in three levels of salinity (normal, 1.2, 4 and 8 dS.m-1) in 2006. Root and shoot length, root and shoot dry weight, Na+and K+concentration in shoot and genotypic code (based on IRRI protocol) were recorded. Tolerant cultivars had high biomass (root and shoot dry weight) and low Na+/K+ratio. Negative and significant correlations were detected among shoot dry weight, biomass and genotype code, while positive and significant correlations were seen among Na+ concentration, Na+/K+ratio and genotype code in 4 and 8 dS.m-1 levels. Significant and robust correlations were seen between mean productivity index (MP), tolerance index (TOL), stress tolerance index (STI), stress susceptibility index (SSI) and harmonic mean (HM) for Na+and mean productivity, stress tolerance index and stress susceptibility index for Na+/K+ratio with genotypic code (P<0.05). Path analysis for 4 dS.m-1 showed that shoot dry weight had a high direct effect on genotypic code. Although biomass had low direct effect on genotypic code, but had high indirect effect on genotypic code via shoot dry weigh. Factor analysis revealed that biomass, shoot dry weight and K concentration explained the most of the total variation.

Efficacy of many herbicides to control broad- and narrow-leaf weeds (grass weeds) in tobacco fields of Mazandaran and Guilan provinces was investigated. The experiment was Randomized Complete Blocks Design in four replications and the following treatments: Eptam (Eradicane 82% EC) at 6 L.ha-1 which incorporated pre-planting (ppi), Trifluralin (Treflan 48% EC) at 2 L/ha ppi, Cycloate (RoNeet 72.7% EC) at 5 L/ha ppi, Pendimethalin (Stomp, 33% EC) at 5 L.ha-1 pre-emergence, Alachlor (Lasso 48% EC) at 5 L.ha-1 pre-emergence., Oxyfluorfen (Goal 24% EC) at 2 L.ha-1 pre-emergence., Oxadiargyl (Top Star 30% EC) at 2 L.ha-1 pre-emergence., Rimsulfuron (Titus 25% DF) at 50 gr.ha-1+2% surfactant (Cytogate) post-emergence, Haloxyfop-P- methyl (Galant Super 10.8% EC) at 0.75 L/ha post-emergence, Cycloxydim (Focus 10% EC) at 2 L.ha-1. Post-emergence, weed-less check. Results showed that weed control in tobacco fields increases yield and quality of tobacco and iconsequently farmers' income. For chemical control of weeds in tobacco fields, if the problem of Cyperus spp. exists, Eradicane herbicide is recommended as a pre-planting incorporated herbicide. If no Cyperus spp. is present, Treflan is suggested to be sprayed, because, it controls broadleaf weeds better. If grass weeds cause problem, one of the two graminicides, Galant Super or Focus, may be sprayed before stem extension.. One or two mechanical weeding also may follow, as needed.

The first step to quantify crop phenology is precise estimation of the parameters, which affect it. These parameters are mainly temperature and photoperiod. This study was conducted with eight sowing dates to quantify response of stem elongation rate (SER) to temperature and photoperiod in wheat (Tajan Cultivar). The regression models fitted to SER against temperature were flat, logistic, quadratic, cubic, dent-like, segmented and curve models. Meanwhile, quadratic, negative exponential and segmented models fitted to SER against photoperiod (these models were used as 21 combined models to describe SER as a function of photothermal day). Root mean square of errors (RMSE), coefficients of determination and regression coefficients of predicted values versus observed ones were used to find the most appropriate model. The results showed that segmentedsegmented function was the best model to describe SER as a function of both temperature and photoperiod. Using this function, the base and optimum temperatures, critical photoperiod and photoperiod sensitivity coefficient were estimated as 4.14oC, 28oC, 14 h and 0.17, respectively. Study the effects of temperature and photoperiod on stem elongation phase indicated that Tajan cultivar has a quantitative or facultative long-day (LDP) response to photoperiod. Biological days required to pass from emergence to stem elongation and emergence to physiological maturity were estimated as 7.66 and 50.31, respectively.

Sever coldness causes damage to the wheat and affect its growth and yield, thereby this experiment was conducted in controlled conditions to investigate freezing tolerance of 29 wheat genotypes. Acclimation treatments (in two levels: acclimation and non-acclimation) were considered in the main plot and combination of temperature (0, -4, -8, -12, -16oC) and genotypes as sub plot. Survival percentage, dry weight and plant height were measured four weeks after freezing in the glasshouse. All these traits were affected significantly by freezing treatments (P<0.001). Reducing temperature under -8 oC caused a significant reduction in the wheat survival percentage. Acclimation alleviated the effects of freezing, so that at -12oC in non-acclimation conditions, dry weight was 72.1 mgr, but it reached to 144.9 mgr in acclimation conditions. Lethal Temperature 50 (LT50) was lower than -15oC in 14 cultivars and higher than -15 oC in 15 cultivars. Among studied genotypes, Alamout, Bezostaja, Falat, Glenson and MV-17 were more cold tolerant than others. In order to determine the cold tolerance of genotypes, conducting complementary experiments in controlled and field conditions could be useful.

In order to evaluate the effect of nitrogen rate and weeding time on weed communities dynamic, a field study conducted in a research farm of Chamran University, Ahwaz. The experimental design was split plot based on RCB with three replications. Nitrogen rates (77, 110, 143 kg/ha) were considered in the main plot and time of weeding (at 5, 8, 11, leaf stage with control and weedy plot) as sub plot. The effects of treatments on weeds were evaluated at two periods: the first period was each time of weeding and the second one was before canola harvesting. The results indicated that nitrogen rate and weeding time had significant effect on weed dry matter and density. The highest weed dry matter with 482 g.m-2, was obtained from 143 kg N.ha-1 and weedy check and the highest weed density with 292 plant.m-2 was obtained from 77 kgN.ha-1 and weeding at 8-leaf stage. In the most cases, weed dominant species, frequency and phenological stages were affected by treatments. However, the effect of nitrogen rate and weeding time at the first period was higher than other treatments. The highest grain yield with 4740 Kg.ha-1 was obtained from 143 kg N.ha-1and weed free plots. Therefore, canola gain yield was increased with increasing of nitrogen rate.

In order to determine yield and physiological response of different wheat genotypes to low temperature, many pot and field experiments were conducted in 2007-2008 at the Plant Physiology Laboratory, University of Kurdistan, and Ghamlo Dryland Agricultural Research Station in Kurdistan province. In both experiments, the experimental design was a randomized complete block in a split plot arrangement with three replications. Experiment was carried out in 2007. Corresponding to three field sowing dates, Oct 1th, Oct 16th and Nov 5th, three pot treatments were performed. Pot treatments were conducted at following temperatures: 20 (control), 10 and 5 oC. Temperature treatments were considered in main plot and twelve genotypes of dryland wheat were assigned to the sub-plots. Both in pot and field experiments, leaf chlorophyll and sugar contents, fatty acids, polyamines and leaf water were significantly affected by treatments. When protein, spermine and oleic acid were measured, no differences were evident among genotypes. Cold stress and genotype had significant effects on the lethal temperature 50 (LT50) and electrolyte leakage. Among the genotypes, Ogosta exhibited the highest cold resistance (LT50), and the lowest electrolyte leakage. Also, Sardari and Ogosta had the greatest grain yield (1178-1210 kg.ha-1), chlorophyll a, chlorophyll b, soluble sugars, protein, putrescine, spermine, spermidine, linolenic acid and oleic acid.

Salinity stress is one of the most important environmental constraints that have been limited agricultural production in Iran. Therefore, introducing suitable cultivars having desirable yield under salinity stress will lead to increase of production efficiency. In order to study the response of spring safflower cultivars to salinity, an experiment was carried out at the Experimental Station of the University of Birjand during 2007. The study was done as a split-plot experiment based on a Completely Randomized Block Design with three replications. Treatments were three times of salinity application (at branching, budding, and flowering) as main plots and three cultivars (Mahali Isfahan (a local variety), PI, and IL111). Salinity stress was induced using well water with an EC equal to 8.6 dSm-1. Results showed salinity had non-significant effects on yield components of cultivars, but the effects followed by these small changes influenced seed and oil yields and oil percentage significantly by time of salinity exertion. There was a significant difference between cultivars in yield and also the most of yield components, with notable superiority of Mahali Isfahan over PI and IL11. Slicing of interactions of cultivars in each time of saline water application indicated that majority of differences between cultivars was related to their response to salinity induced at budding, with Mahali Isfahan had the highest seed weight and seed number. than others. In general, it seems that Mahali Isfahan cultivar had more adaptability to irrigation with saline water. If this cultivar is irrigating with fresh water during reproductive phase, especially between budding to full flowering, it can producea reasonable seed and oil yields.

Seed production, as well as other economical and ecological attributes, is an important character in grasses. Knowledge on the genetic diversity of seed yield and yield components on Iranian tall fescue accessions, as a high productive and adaptive grass is limited. This experiment was conducted to investigate the genetic diversity of seed yield and seed components, determine relationships between traits and identify components of seed yield in 46 tall fescue accessions using some multivariate statistical methods under field conditions. Results indicated that there is a broad genetic diversity in this germplasm for seed yield and its components, which can be employed in breeding programs. Correlation coefficients of seed yield with all measured traits were positive and significant and the highest one was found for seed per plant (0.91). Seed yield was positively correlated with flag leaf width and length. Results of factor analysis showed that to seed yield in tall fescue, not only size and efficiency of reproductive system, but also flag leaf characters are important. Based on regression methods, in an indirect selection index, the efforts should be focused on panicle per plant and panicle fertility.

Fusarium head blight (FHB) is an important disease in wheat worldwide that reduces grain yield, quality as well as contaminates grains to the mycotoxins. Thirty spring wheat genotypes including 28 bread wheat and two durum wheat genotypes were evaluated for FHB under a randomized complete block design with three replications. Grain yield and its components were evaluated by using two environmental conditions including disease-free environment (created by Tilt fungicide) as a control and disease-infested environment by hand sporing. The disease incidence (DIC), disease severity (DSV), Fusarium damaged kernels (FDK) and stress susceptibility index (SSI) were evaluated as four types of resistance indices. Combined analysis showed the significant reduction of grain yield via grain weight that was affected by FHB. The bi-plot diagram for ISK (Incidence-Severity-Kernels) and SSI (Stress Susceptibility Index) showed that the Falat cultivar was the most susceptible and Sumi3 and Frontan were two most resistant cultivars to yield reduction.

Effect of different amounts of foliar- and soil- applied N were evaluated in a factorial arrangement of RCBD with three replications at the Agricultural Research Station of Gorgan in 2004-2005 growing season. Two promising lines of bread wheat, two levels of foliar application of nitrogen (0 and 5%) at tillering and booting stage, with five rates of 0, 45, 90, 135 and 180kg N/ha as urea were used. ANOVA results showed that grain and biological yield increased from 4130 and 9529 kg/ha to 5399 and 13400 kg/ha at 0 and 180kg N/ha, respectively. Foliar application of nitrogen did not affect grain yield of studied lines. Grain yield was not significantly affected by N foliar application, while it increased yield about 120 kg.ha-1. With increasing of N rate, spike length increased significantly. Increasing of grain yield due to soil-applied N might be attributed to increase in number of seeds per spikes.