Iranian Journal of Field Crop Science
Year:2010 | Volume:41 | Issue:3|Papers Count:27

Water deficit and low nitrogen content of soil are the two major yield limiting factors in most maize (Zea mays L.) producing areas. The objective of the current research was to evaluate the relationships between photosynthetic water and nitrogen use efficiency at different levels of soil moisture and nitrogen contents. A factorial experiment, based on completely randomized design with 3 replications was conducted in the greenhouse of College of Agriculture, Shiraz University in the spring and summer 2006. The treatments consisted of 4 different levels of soil moisture based on field capacity (1.2 FC, FC, 0.8 FC and 0.5 FC), soil nitrogen at two levels (180 and 60 kg ha -1) and 2 single crosses of maize hybrids (KSC 700 and KSC 704). The results revealed that KSC 700 had a higher photosynthetic water use efficiency compared to KSC 704 under the water and nitrogen stressed conditions, this being due to higher photosynthetic nitrogen use efficiency. Furthermore, the present research indicated a negative correlation between photosynthetic water use efficiency and photosynthetic nitrogen use efficiency under water stress conditions. Overall, it appears that KSC 700 hybrid might be superior under low water and nitrogen availability conditions, compaed to widely grown KSC 704 hybrid.

Plant growth is greatly influenced by environmental stresses including water deficit, salinity and extreme temperatures. Hence, the identification of genes especially regulatory ones whose expression enables plants to adapt to or to tolerate these abiotic stresses, is very essential. MYB proteins are a superfamily of transcription factors that play regulatory roles in developmental processes and in the defense responses in plants.Members are characterized by having a structurally conserved DNA-binding domain, the MYB domain. To investigate the role of these regulatory factors and their expression pattern during stress in wheat, a number of candidate MYBs, were selected and after sequence analysis, were used for Real Time RT-PCR analysis. To extract total RNA, 13 day old seedlings of wheat were treated separately with 200 mM NaCl at 4oC tempreture for 0, 6 and 24h and than their roots as well as their shoots were subjected to sampling. Phylogenetic analysis of a number of these genes with Arabidopsis and Rice reference sequences, classified them into three groups. Also, qRT-PCR analysis revealed that the expression pattern of most of the selected genes changes in response to stress, and which can be categorized into several groups based on stress and on tissue.The results of this study can be utilized as a useful data source in the projects related to MYB genes cloning or transformation in wheat.

Salinity problem is continuously increasing in the arid and semi-arid regions of Iran. To effectively utilize germplasm resources in breeding, it is necessary to characterize and evaluate genotypes for the desirable traits and as well for salinity tolerance. Salinity tolerance of 80 wheat landraces from different parts of Iran was studied in two steps. At first, the degree of salnity tolerance of the selected genotypes was evaluated for grain yield in saline soil (up to 10dS.m-1) at Agh-ghela, in comparison with grain yield in potential conditions in Gorgan over two years (1998-2000). One-third of the genotypes were selected based on grain yield, salt tolerance index and adaptability to region. The selected genotypes were then evaluated in 150mM NaCl in Hoagland’s solution. Stress Tolerance Index (STI) was significantly and positively correlated with leaf K+/Na+ratio in salt-stressed plants, while, this index negatively correlated with plant height, leaf burning, days to heading and days to maturity in non-stressed plants and leaf sodium in stressed plants. Gene bank genotype No.24, Mahdavi, cross Arvand and Ghods cultivars had relatively high grain yield, high STI, high leaf K+/Na+ratio and low leaf sodium, indicating that they can be utilized in wheat breeding programs as planned for the saline regions.

The effects of inoculation of thiobacillus and the type of nitrogen fertilization (urea and ammonium sulphate fertilizers) on yield and yield components of rapeseed cultivars (Okapi, SLM 046 and Reagent * Cobra) were studied. The experiment was carried out as spilit plot factorial in randomized complete block design with 4 replications in Shahrood University of Technology. Reagent * Cobra cultivar produced 4400 Kg/ha which in comparison with the other cultivars was the highest. The effect of thiobacillus on yield and some other traits was significant. Thiobacillus application improved seed yield for about 12.2 percent in comparison with check cultivar. The effect of thiobacillus application on plant height, number of pods in main stem and secondary branch as well as number of leaves in plants was significant. While the effect of nitrogen source (urea and amonium sulphat) on yield was not significant. Interaction between application vs. no application of thiobacillus and cultivars was significant regarding seed yield, length of secondary branch and length of pod on the secondary branches.

To study the effect of planting dates and Genistein application on nitrogen content and nodulation of three annualMedic species (Medicago polymorpha cv. Santiago M.rigidulacv. Ragidula, and M. radiata cv. Radiata), an experiment was conducted during 2005-2006 in the Research Farm of Faculty of Agriculture, Shahed University, Tehran.The treatments were arranged as split split plot in a randomized complete block design with four replications. Planting dates (February 20, March 1 and 11) were randomized to main plots while three annual medics allocated to sub-plots plus Genistein (0 and 20mM) randomized to sub-sub-plot units. Plant nitrogen content, nodulation and other traits were significantly affected by species.M. polymorpha was affected more than other species with respect to dry nodule weight, nodule number and number of nodules in cluster, nodule cluster number as well as nodule diameter.Medicago rigidula exhibited a better resistance to cold than other varieties, with its forage yield and nitrogen percent higher than M. polymorpha. Therefore, M. rigidula may be better adapted to cold zones. Twenty mmol of Genistein remarkably affected nodulation and nitrogen percent of annual medics as compared to control. The results indicated that Genistein modified the negative effect of low temperature on nodulation and nitrogen percent of annual medics. Nodulation and nitrogen content (percent) increased in all varieties for the first planting date. This emphasizes that Genistein had considerable effect on cold resistance establishment in varieties for improving nodulation and increasing plant nitrogen (percent) at farm growing conditions.

Studies on manipulating the source-sink relationships during postanthesis in wheat have shown inconsistent results, concluding that wheat yield could be either sink- or source-limited. Most studies have reported data of grain mass as an average of all grains preventing the recognition of different sensitivities to the availability of assimilates of grains placed at different positions within the spike. The response in growth and final mass of grains from the base, middle and apical part of spike along with the response in weight of individual grains from different positions within the central spikelets to decreases in assimilate availability was studied by moderating source-sink relationships during the grain growth period of wheat. Pot experiment was carried out, under natural conditions in the greenhouse areas of the College of Agriculture, University of Tehran, Karaj, in 2007-08 cropping season. Treatments consisted of 7 cultivars of bread wheat (new and old cultivars from moderate, cold and warm climates of Iran) and 7 defoliation treatments carried out at late joining stage and 20 days after anthesis.Treatments were arranged in 3-replicated factorial combination based on an RCBD design. In general, significant decrease of the peduncle weight was observed in defoliation treatments as compared with the control plants. In other words, decrease in the source strength through defoliation resulted in more consumption of water-soluble carbohydrates stored in the stem through kernels. On average in all cultivars, defoliation decreased grain mass in the base, middle and apical parts of the spike, of which the response of the apical part was more significant. Regarding the effect of defoliation on the weight of grains placed at different positions within the spike and individual grain weight in various positions of central spikelets, there was no obvious difference observed among cultivars. In old cultivars, defoliation did not affect grain weight at any spike position whereas, in the new ones, grain from some parts, particularly apical parts, was affected by defoliation. Significant decrease in individual grain weight was observed only for G3-positioned grains at severe defoliation treatments, but G1 and G2 positioned grains did not respond even to severe defoliation treatments.

Seedlings of five canola genotypes (Hyola308, Hyola 401, Hyola 60, Optlon 50, and RGS003), were grown in Hoagland nutrient solution containing S1=0, S2=100, S3=200 and S4=300 mM NaCl in controlled environment. Such antioxidant activities as Catalase (CAT), Ascobrate Peroxidase (APX) and Guaiacol Peroxidase (GPX), as well as osmolyte concentration (proline), Chlorophyll fluorescence and some enzyme activities of nucleic acid metabolism were determined in the plants' shoots and roots 30 days after induction of salinity stress. Results indicated that, application of stress significantly affected plant growth components such as Fresh (FW) and Dry Weight (DW) in canola genotypes. Among the genotypes, RGS003 experienced the highest reduction of FW and DW in the S3 treatment. By increasing NaCl levels from 0 to 300 mM, the activity of two antioxidant enzymes (APX and CAT) increased in shoot and root while GPX decreased in all the genotypes. The increase in salinity stress, increased proline concentration in both root and shoot tissues of canola genotypes. Hyola401 genotype carried the maximum concentration of proline in root and shoot in S3 treatment. Along with increased salinity stress in all the studied plants, salinity significantly increased the level of the total nucleic acid and the activity of DNase I in all the salinity treatments. Moreover, at the S3 level, RGS003 carrying a maximum concentration of nucleolytic enzyme.

In order to investigate the environmental factors including temperature, moisture, and plant hormones on dormancy breaking of seeds ofXanthium strumarium L. a number of experiments were conducted.X. strumarium seeds were dormant soon after being harvested. Seed germination of cocklebur increased through a combination of cooling, temperature fluctuations following ripening. Most seed germination (82.5%) occurred in buried seeds in 5-7 cm depths of soil in natural conditions for 4 months in addition to keeping them in cool room temperature (5±2) for 3 months, followed by retaining the seeds on the surface of soil (0 cm) in field conditions for 6 months. A combination of cold (5±2NC for 2 months) and GA3 resulted in a slight significant increase in seed germination of X. strumarium L. (p<0.05). Washing of seeds, immersing them in hot water and scarification (crust split of seeds) had no significant effect on seed germination. Sulfuric acid (%98), scarification and Ethephon did not show any effect on seed germination (p<0.05). In all the treatments, between two seeds treated through burring only the larger seeds germinated while none of the treatments resulted in the germination of smaller seeds. Based upon on the experimental treatments in this study, it can be said that dormancy of X. strumarium L. seeds is a physical as well as a physiological dormancy phenomenon.

Plants are always exposed to vast aspects of either environmental biotic or abiotic stresses and those stresses affecting the plant growth and therefore crop production.Molecular and physiological mechanisms influence plant resistance to environmental stresses, therefore the identification of these mechanisms can be an important step in challenging the damages. In this study, plant physiological responses of two cold sensitive bread wheat cultivars, namely: Bayat and Darab1 vs. two cold resistant cultivars named Alvand and Shahi were studied. The amount of relative water content, chlorophylls, carotenoids as well as free proline amino acids were assessed. In addition, partial of the gene responsible for the responses to cold stress in the four wheat cultivars were isolated. The results indicated that the relative water content and the level of chlorophylls as well as carotenoids were significantly reduced in response to the stress.This reduction was more pronounced in the case of the sensitive cultivars. Furthermore, cold stress increased the free proline content. Bioinformatical analysis of the translation of 500 nucleotide sequences revealed that they contained a conserved 57 amino acid region with three ß-sheet and oneV-helix, as well as a valine amino acid at position 14 along with a glutamic acid at position 19. The sequences were recorded in NCBI GenBank.

Glutathione Transferase (GST) is a family of multifunctional detoxification enzymes which are mainly cytosolic that detoxify natural and exogenous toxic compounds through conjugation with glutathione tripeptide. Its conjugates can be transported to vacuoles or apoplast. These conjugates are generally less toxic than the parent compounds. Glutathione transferase is identified and isolated from many organisms including different species of plants. In this study, isolation and characterization of GST genes was carried out from eleven bread wheat cultivars for the first time. DNA extraction, primer design, PCR, Electrophoresis, column purification, DNA sequencing and bioinformatics analysis led to on identification of new sequences of glutathione transferases. These sequences were submitted to NCBI GenBank with FI131235, FI131236, FI131237, FI131238, FI131239, FI131242, FI131243, FI131244, FI131246, FI131247 and FI131248 accession numbers for TaGST of Alvand, Bayat, Besostaya, Chamran, Darab1, Mahouti, Omid, Roushan, Sardari, Shahi and Zarrin bread wheat, respectively. These sequences prepare the basis for gene transfer of glutathione transferase to sensitive plants in oxidative stresses and xenobiotics.

This experiment was conducted to evaluate the effects of different sowing densities and nitrogen fertilizer rates on quantitative and qualitative corn forage yield in an agroforestry system with orange trees. The treatments consisted of 4 nitrogen fertilizer levels of 0, 100, 200, and 300kg N/ha (allocated to main plots) and 4 sowing densities of 80000, 110000, 140000 and 170000 of corn seeds (plants) per hectare (allocated to sub plots). The experimental plots being kept either weed free or weed infested were allocated to sub-sub plots. The treatments were arranged as split-split plots in a randomized complete block design with three replications. The forage dry matter yield followed an increasing trend as nitrogen fertilizer and sowing density increased. The highest forage dry matter of around 34000 kg/ha was achieved at 170000 plants/ha while receiving 300kg/ha of nitrogen. The largest orange fruit diameter was observed in 100Kg N/ha and 80000 plants/ha which was not significantly different from 300 kg of N/ha treatment.

An investigation of chlorophyll quick fluorsence variations was made in the Reaserch Field of Islamic Azad University- Karaj in 2007. The experimental design was a split plot one in form of a complete randomized block design with 4 replications.Drought stress was cosiderded in three levels of 40%, 60%, and 75%, on the basis of depletion of soil moisture as the main factor and the factor of microelements in three levels of 0, 3, 5 lit/ha. The evaluated traits were chlorophyll fluorsence parameters, RWC, chlorophyll content and cell memberane stability, as well as grain yield in two stages. Results, indicated that the stress effects on F0, chla, chlab and GY and also FV/FM, and chlb were significant at the first stage, while in the second stage they were significant on F0 (p<0.05), and while in other parameters they were non significant.The triat means of FV/FM, chlab, chlb, chla andcell memberan stability declined while F0 increased as drought stress levels increased (at the first stage), but at the second stage F0 increased although Fv decreased. At the first experimental time microelements' effects were significant on F0 (p<0.05) and EC (P<0.01) while at the second stage, they were significant on F0 (p<0.05). The means indicated that F0 increased in each stage, but cell membrane stability decreased although microelement levels increased. FV/FM, chlab, chla and EC had the highest while F0 the lowest correlation coefficient with grain yield. At the second stage the highest correlation coefficient was observed with FV/FM, FV, FM and the lowest with F0 with GY. Interaction effects were significant on EC (p<0.01) at the first and on F0 (p<0.05) at the second experimental time. Result showed that, masured parameters under drought stress can act as an index for determination of intensity of stress. Also FV/FM, FV, and even Fm are suitable for an investigation of intensity stress.

An experiment was conducted to determine the aging mechanism in safflower seed using natural aging treatment (storing seed at room temperature for six years) and accelerated aging (incubating the seed at 41oC and close to 100% relative humidity for 4, 8 and 12 days). The results indicated that both natural and accelerated aging reduced germination percentage, seed vigor and activity of Catalase (CAT), Peroxidase (POX) and Ascorbat Peroxidase (APX). The results also show that Malondialdhyde (MDA) content, electrolyte leakage and Mean Time to Germination (MTG) enhanced under natural and accelerated aging. The germination percentage in accelerated aging (from 94 percent in control) reached 64, 5 and 41 percent within 4, 8 and 12 days of treatment respectively. The increase in MTG was higher in natural aging than in accelerating aging. The decrease in ascorbat peroxidase activity in the aging treatments were higher than those in catalase and proxidase activities. Decrease in antioxidant enzyme activity resulted in enhanced Reactive Oxygen Species (ROS) and lipid peroxidation. Lipid peroxidation and membrane damage resulted to decrease seed germination and vigor. A high correlation was obtained between MDA content and germination as well as seed vigor in both accelerated and natural aging suggesting that lipid peroxidation plays an important role in safflower seed deterioration in natural and as well in accelerated aging.

Synthetic plants as well as wild crop species are valuable genetic resourses. To determine the genetic variation in triticale, tritipyrum as well as wheat lines, genomic DNA of this amphiploid including Thinopyrum bessarabicum and durum wheat were amplified using 32 random and 22 semi random primers. Primers that could produce clear, polymorphic and repetitive bands are used for determination of similarity matrix and dendogram based on Jaccard similarity coefficients and UPGMA algorithm. The similarity coefficients were in the range of 0.01-0.55, 0.02-0.63 and 0.04-0.53 for random, semi-random and a combination of random and semi-random primers, respectively, indicating a broad genetic divergence among these three amphiploids, durum wheat andTh. bessarabicum. For the combination of random and semi-random primers, average genetic similarity between triticale premising lines, tritipyrum primary lines, andTh. bessarabicum were found to be 0.179, between tritipyrum primary lines and wheat breeding cultivars 0.194 and between triticale premising lines and wheat breeding cultivars 0.161. Steward tetraploid wheat exhibits the highest genetic distance from 4103 triticale line. The triticale lines 4103 and 4116 exhibited the lowest genetic distance between each other. La (4B) 4D/b tritipyrum line has the highest genetic similarity with chains spring wheat cultivar. St/b and Cr/b tritipyrum lines had the highest genetic similarity with the paternal line (Thinopyrum bessarabicum). This study confirms the efficiency of semi-random than random primers, as well as the combination of random and semi-random primers than their sporadics in an estimation of genetic diversity.

Grand cherry (Physalis divaricata) is considered as the most problematic weed in sugar beet farms in Alashtar county, Iran. Special experiments involving chemical control of this weed were carried out using trifluralian, etalfluralian and chloridazon herbicides under laboratory conditions. The experiments were designed in a randomized complete block design in three replications, carried out in 2007. The study showed that more than 50 percent of the weed germination was obstructed by chloridazon herbicide application showing a significant difference with control at 5 percent level. Trifluralian, etalfluralin and mixture of the two herbicides treatments did not show any significant difference in weed germination as compared with control. But all the seedlings were demolished except those in control after a passage of three weeks. It became euident that these herbicides can obstruct the root development growth of this weed. A study of the growth and density of this weed in wheat fields showed that wheat crop can effectively decrease the density as well as growth of the weed grand cherry.

Through an application of genetic engineering, genes from a soil bacterium Bacillus thuringiensis (Bt) which confer resistance to pests were transferred into rice. Successful employment of genetic engineering in traditional breeding programs is dependent upon stable transmission of transgene in transgenic varieties. Three different segregating F2 populations were developed from a cross between each one of the transgenic lines namely: Tarom Molaii, Neda and Nemat and Sang Tarom while the segregation mode of cry1Ab gene being studied in these populations. The results of phenotypic assay in field and genotypic analysis (employing PCR in laboratory on the different F2 populations) revealed monogenic segregation ratio forcry1Ab gene. The results indicated single copy integration ofcry1Ab gene in the genomes of transgenic Tarom molaii, Neda and Nemat. This illustrates predictable segregation pattern of cry1Ab gene in transgenic plants. In addition, the data obtained imply that integration of cry1Ab gene in the genome of the studied transgenic lines is stable and can be successfully transmitted to successive generations. So, these transgenic lines could be well employed for improving pest tolerance of varieties in integrated pest management programs.

To estimate the optimum and effective amount of nitrogen fertilizer for quantity and quality improvement of three new durum wheat lines, this research was conducted in Gachsaran Dry-land Agricultural Research Station for a duration of 4 years (2003- 2007). The study was performed as a factorial expriment, using a randomized complete block design with 4 replications. Two factors of: 4 nitrogen rates [0 (N0), 25 (N25), 50 (N50) and 75 (N75) kg ha-1] and three durum wheat lines (L1: 43210 Karaj (Capieti), L 2: MNA-1/RMF7 and L3: SORA/2 * PLATA-12) were taken into condsideration. Results indicated that nitrogen rates exherted significant effects on plant height, spike length, number of spikes/m2, number of grains/m2, harvest index, grain yield as well as grain protein content. There was a significant difference among these three lines in the above respects. Capieti (L1) bore a higher number of grains per spike (50.52), harvest index (46.15%), higher grain yield (3.491 t. ha-1) and grain protein content (11.63%) followed by line L2. Among these lines, L 2 had a higher plant height (86 cm) and with respect to spike length, the two lines of L2 and L3 produced the longer and the shorter spikes respectively. On the other hand, nitrogen rates presented significant differences in all the evaluated traits with the exception of 1000-grain weight and harvest index. Higher grain yield (3.85 t. ha-1) and higher grain protein content (12%) were obtained from the nitrogen treatment of N75. The study on relation of grain yield and harvest index indicated that for each 1% increment of harvest index, grain yield increased approximately 0.076 t ha-1. Finally, to obtain higher grain yield per unit area, higher grain protein content and for prevention of further environmental pollution caused by inappropriate application of nitrogenous fertilizers, a pure nitrogen rate of 75 kg ha-1 with application at planting time is recommended for these new lines at this site as well as for other similar regions.

In order to study the effect of deficit irrigation at reproductive growth stages on growth and grain yield of four sunflower cultivars namely: Azargol, Allstare, Alison and Euroflor, an experiment was conducted during the 2007 growing season at the Experimental Field of the Agricultural Faculty of Bu-Ali Sina University. The experimental design was a split plot one, based upon a randomized complete block arrangement with three replications. The irrigation levels included: full irrigation, deficit irrigation by withholding irrigation at heading, flowering, seed filling, at heading plus seed filling as well as at flowering plus seed filling stages. The indices of Total Dry Weight accumulation (TDW), Leaf Area Index (LAI), Crop Growth Rate (CGR), Harvest Index (HI), Biological and Economical Yield (BY and EY) were assessed. The results indicated that the highest LAI (4.0), CGR (40.1 gm-2 d-1) and TDW (1537.9 g.pl-1) were obtained from Euroflor cultivar when fully irrigated. Euroflor had the highest of these values in deficit irrigation treatments. Deficit irrigation in flowering stage had high decreasing growth indices especially in NAR as well as in RGR and HI. Euroflor cultivar and fully irrigated treatments exhibited the highest BY (1012.7 and 1168.2 g.pl-1 respectively) as well as HI (40 and 42% respectively). The highest EY was obtained from intraction of Euroflor cv. in full irrigation (500.8 g.pl-1) and Euroflor cv. with deficit irrigation at seed filling stage. The same results were obtained for other cultivars in their fully irrigation treatments. The lowest EY belonged to Azargol and Alison in twice withholding irrigation at flowering and seed filling stages, and also in Alison when twice withholding its irrigation at heading and seed filling stages. Finally the treatments of twice withholding irrigation, and deficit irrigation at seed filling stage exhibit the highest and the lowest negative effect on growth and yield of sunflower respectively. Euroflor cv. is finally suggested as a successful cultivar with the highest growth and productivity under various irrigation conditions.

Evaluation of genetic diversity is a considerable approach to screen within indigenous rhizobial population for compatible, highly effective strains, which can be further utilized as rhizobial inoculums. Genetic diversity of Rhizobium isolates from three clover species grown in soil samples of seven different geographical regions in Iran was investigated by Repetitive extra genomic palindromic fingerprinting (Rep-PCR) method. Out of 152 isolates tested in the study, 22 were identified as different strain types. Genome analysis of rhizobial isolates, as based on the fingerprinting profiles and the relating dendrogram, revealed considerable heterogeneity among isolates with different host species' origin. The results demonstrate Rep-PCR fingerprinting method as a powerful technique to differentiate among closely related strains ofRhizobium leguminosarum bv. trifolii. The results also suggest that clover species tend to preferably absorb their rhizobial symbionts.

To study the effect of planting rates and harvest time on forage quality of maize in maize-cowpea intercropping, an experiment was conducted at the Research Farm of Zabol University, during 2007 and 2008. The experiment was arranged in a 7x2 factorial one in complete randomized block design with 4 replications. The two factors consisted of seven planting ratios of maize and cowpea (100: 100, 100: 50, 50: 100, 50: 50, 25: 75, 75: 25 maize – cowpea intercropping and a sole crop of maize) vs. two harvest times (milky and doughy stages of maturity). Planting ratios and harvest times were significant for all traits except for NDF. Maize-cowpea intercropping yielded higher forage quality than the sole crop of maize.100: 100 and 100: 50 planting ratios of maize and cowpea in milky stage of maturity yielded the highest forage quality.Maximum variation in DMD could be attributed to the ADF. Ideal forage could have lower ADF and higher DMD, CP, WSC, Ash, leaf to stem as well as seed to forage ratios.