Iranian Journal of Field Crop Science
Year:2010 | Volume:41 | Issue:4|Papers Count:23

Sainfoin (Onobrychis sativa), a forage legume, is worth attention because of its production and superior quality among pasture and hay forage crops in Iran. Sainfoin forage yield may be reduced by different levels of salinity. Increasing forage yield in saline environments through plant breeding could partially compensate for this shortcoming if sufficient genetic diversity and heritability be available under stress.This experiment was conducted to evaluate forage yield and agronomical attributes, estimate genetic parameters and determine superior genotypes for salt tolerance in advanced breeding projects. Thirty genotypes were evaluated using a randomized complete block design during 2005 and 2006. Results showed that there are significant differences among genotypes for yield and some morphological traits indicating a broad genetic variation in this germplasem. Genotypic coefficients of variability for forage yield and for the number of stems were highest during the first year, while these coefficients were highest for number of stems and panicle per plant during the second year. The highest estimates of heritability were observed for powdery mildew susceptibility and plant height, while the lowest were for days to seedling emergence and canopy diameter. Applying cluster analysis to the studied attributes, three groups were obtained which the most tolerant genotypes and the least similar accessions were identified to be further employed in the future breeding projects. Finally, it can be concluded that there are sufficient genetic diversity and heritability for yield and other related traits in the studied sainfoin germplasem grown under salt environments indicating the efficiency of selection methods for developing tolerant varieties.

A study was conducted to evaluate the effects of Plant Growth Promoting Rhizobacteria (PGPR) inoculants including four strains of Azotobacter chroococcum, Azospirillum lipoferum, A. brasilenseand Pseudomonas fluorescence on dry matter accumulation of late maturing Maize (Zea mays L.) hybrids, SC704, SC700 and a promising single cross B73xK18. A factorial experiment was conducted in research field of Seed and Plant Improvement Institute (SPII) of Karaj in 2004 and 2005. In this study, hybrids seeds were inoculated by various PGPRs. At physiological maturity, plant and stem, leaves, tassel, ear, husks, cob and grain dry matter and harvest index were determined. Results revealed that, except tassel and husks dry matter, other traits affected by year, hybrid and PGPR. SC704 and SC700 which inoculated by all bacteria exhibited the highest plant, stem, leaves, cob and ear, dry matter and harvest index in the second year. Also in two years, three hybrid seeds inoculated by all bacteria had the most effect on dry matter partitioning. This treatment caused 48, 15, 4 and 30% increase in whole plant, leaves, stem and grain dry matter, respectively. Moreover, 34% increase in harvest index was detected. The results indicated that studied hybrids dry matter partitioning pattern affected by PGPR. Also application of PGPR changed plant organs dry matter partitioning trend to sources and sinks. Also the rate of this increase for leaves as main photosyntetically organs and ear was higher resulting in higher harvest index.

To improve bread wheat salt tolerance, new genetic sources of salt tolerance are indispensable, and this requires a screening of wheat germplasm.In order to evaluate bread wheat germplasm, 34 accessions including; hexaploid wheats (AABBDD), tetraploid (AABB) and wild relative diploids (DD and AA genome) collected from different regions of Iran were evaluated under normal vs.salinity stress (NaCl) conditions, using a factorial experiment in a hierarchical design with three replications.The assessed characters were biological dry weight, tissue Water Content (WC; shoot H2O per dry shoot mass), Na+ and stress tolerance index (ST). Stress tolerance was significantly correlated with tissue Na+ concentration and WC. The estimated coefficient of genetic variability (%CVg) via expected mean squares showed that there is a significant genetic diversity in population. Cluster analysis on the basis of Ward's method rendered all the accessions clustered into four clusters at a distance of 7.4.There was a good consistence between clustering results and %CVg. Some accessions were observed with a high shoot Na+ concentration and a high level of ST while some with low Na+ along with high ST. Therefore, breeding for improved ST in bread wheat needs a selection for traits related to both Na+ exclusion and tissue tolerance as well as pyramiding of both into breeder’s lines, using Marker-assisted selection that has the potential to accelerate this breeding process.

To study the molecular basis for resistance of Lolium rigidum populations (from Fars Province) to Aryloxyphenoxy Propionate herbicide through dCAPS method, an experiment was conducted at the Biotechnology Laboratory of Shiraz University.Eighteen populations of L. rigium suspected of herbicide resistance, from Zarghan, Fasa. Noorabad and Firoozabad areas which had survived a recomended dose of Clodinafop-propargyl herbicide were tested through molecular assay. dCAPS method was carried out in three steps including DNA extraction, PCR and enzyme digestion to determine the molecular basis for herbicide resistance. The results showed that among these populations, 11 were resistant homozygous, 3 were resistant heterozygous and four ones susceptible. It is probable that substitution of isoleucine by leucine at the equilalence of residue 1781 of Acetyl CoA Carboxylase (ACCase) and mutation at position 1781 of ACCase enzyme has resulted in the high resistance in someL. rigidum populations against the mentioned herbicide.

To evaluate the effect of seeding rate on important agronomic traits in three winter rapeseed (Brassica napus L.) cultivars, two field experiments were carried out as split plot arrangement in a complete block design with three replications during 2006-2008 growing seasons. Three rapeseed cultivars (Okapi, Modena and Licord) and three seeding rates (6, 8 and 10 kg/ha)) were randomized in main plots and in sub-plots, respectively. The results revealed that rapeseed cultivars had significant differences for all traits except for grain oil content. Licord had the highest grain yield (4213.72 kg/ha), harvest index (31.07%), and biological yield (13071.4 kg/ha). Significant differences were observed among different seeding rates for some such traits as grain number per silique, silique number per plant, plant height, secondary branch number per plant, days to maturity, grain yield per plant, and dry matter remobilization. The highest grain yield and dry matter remobilization were obtained for the 6 kg/ha seeding rate treatment.Increased seeding rate diminished grain yield, yield component and dry matter remobilization from the aboveground plant parts to grain. Licord had the highest grain yield and harvest index on 8 (88 plants per m2) and 6 (66 plants per m2) kg/ha seeding rates, respectively. There were positive significant correlations between grain yield and the most of the traits namely 1000-grain weight, grain number per silique, silique number per plant, plant height, secondary branch number per plant, days to maturity, maturity duration, grain oil content, oil yield, grain protein content, harvest index, biological yield, grain yield per plant and dry matter remobilization. Also the correlation coefficient between dry matter remobilization and all the traits except days to end of flowering and grain oil content was positive and significant. According to the results obtained in this experiment, it seems that Licord variety accompanied by the 6 kg/ha seeding rate to be recommendable in Arak region, as well as in similar agroecological conditions.

Temperature is an importan environmental factor that inevitably determines the extent and geographical range of plants. In this study, the chilling induced responses of 11 desi chickpea genotypes were surveyed under growth chamber conditions to screen for chilling tolerance. Electrolyte leakage (EL) and lipid peroxidization (Malondialdehide (MDA)) methods were employed for the purpose. Data analysis revealed that there existed significant differences among genotypes for treatments 23 and -10oC. Low temperature regime (-10oC for 15 min) resulted in increasing EL and MDA in all the genotypes except in 4322 and 4715. MDA analysis introduced genotypes 4715 and 4322 as cold tolerant candidates. Further analysis at -12oC revealed 4322 (showing low ELI and MDA) potentially recovered after coming back to optimum temperature. These were identified as good cold-resistant candidates which can be employed in future trials, whereas genotype 4715, because of undergoing severe damage, didn’t continue to survive even after initial temporary recovery. Results showed the first physiological and biochemical responses of cell membranes in the tolerant genotypes under cold stress and that ELI and MDA can be employed as cold tolerance markers in evaluation of genotypes in short duration low temperatures.

Genus Onobrychis comprised of many cultivated as well as wild species is adapted to different regions of Iran. This study was conducted to evaluate the karyotype characteristics of seven Onobrychis species, employing the analysis of metaphase chromosomes of mitotic cells. Results revealed that the species O. melanotricha (from Semirom and Feriedan)‚ O. sativa (from Arak and Boroujen) with 2n=28 chromosomes and O. sativa (from Najafabad) with 2n=32 chromosomes were tetraploid while the other species bearing 2n=14 chromosomes were diploid. The basic chromosome number varied between x=7 and x=8. According to Stebbins' classification, species O.melanotricha (Semirom)‚ O. melanotricha (Feriedan), and O. sativa (Najafabad) were classified as symmetric class of B while the others as A. The results of ANOVA showed significant differences among the species for most of studied traits. By cluster analysis as based upon karyotypical characters‚ the species were classified in three clusters. The lowest distance was obtained between the two species of O. melanotricha (Semirom) and O. melanotricha (Feriedan) while the widest between O. melanotricha (Fereidan) and O. sativa (Brojen). Using principal component analysis, the first two components justified 85 percent of the total variance. In the first component, chromosome size while in the second one centromer position maintained the most important justification of the total variance.

Field experiments were conducted in Amirkabir sugarcane Agro-industry (Khuzestan province, Iran) farms to evaluate the efficacy of integrated chemical and mechanical methods in controlling weeds. Experiments were carried out in a split plotrandomized complete blocks design with four replications. The main plot consisted of four mechanical treatments, namely: hilling up, sweep cultivator, disc cultivator vs. no tillage. The sub-plots included six herbicide treatments (tebuthioron (Tebusan®) +ametryn, trifluxysulforon-sodium (Envok®) +ametryn, ametryn-trifluxysulforonsodium (Krismat®) +2, 4-D-MCPA, mesotrion (Lumax®), Ametryn+2, 4-D-MCPA & Control). Evaluations consisted of a grading of weed control and sugarcane crop appearance, a measurement of weeds’ dry weight as well as crop’s yield, quality and quantitywise. Results indicated that a hilling up treatment can merely act as a replacement for herbicide by 75% of control, whereas sweep cultivator and disc cultivator acted some measures of 15% and 5% of control respectively with the need for band spraying as a complement. Mixtures of Krismat®+ (2, 4-D+MCPA), Envok®+ametryn and Lumax+cytogate® provided a good control of weeds, especially in combination with mechanical control measures, but they didn’t reflect any significant difference with ametryn+2, 4-D as a standard control measure. All the herbicides, as well as their mixtures had significant differences with the untreated control. Overall, it is concluded that mechanical control integrated with band spraying is a very cost effective method in sugarcane weed control.

To evaluate the effects of methanol and drought stress on chlorophyll fluorescence parameters, chlorophyll and relative water content in sugar beet, a study was conducted in 2008 in Maahdasht (Karaj, Iran). Aqueous solutions of 0 (control), 7, 14, 21, 28, 35% (v/v) methanol with each solution containing 0.2% glycine and a second factor, namely drought stress (irrigation after 70% depletion of available water) and normal irrigation (irrigation after 40% depletion of available water) constituted the treatments. The solutions were sprayed overhead, 3 times in two week intervals on foliage parts of the crop sugar beet. Results indicated that there was no significant difference between levels of solution on minimum chlorophyll fluorescence (F0), fluorescence variavle (FV) and maximum chlorophyll fluorescence (FM), but there was a significant difference observed between levels of solutions on photochemical capacity of photosystem 2 (FV/FM) at a 5% probability level. Analysis of variance revealed that before a third foliar application, chlorophyll content did not show any significant difference, whereas there was a significant difference observed among levels of solutions on chlorophyll content after the third application at a 5% probability level.Also results indicated that drought stress significantly decreased photochemical capacity of photosystem 2 (FV/FM), fluorescence variavle (FV) and maximum chlorophyll fluorescence (FM) at 5% probability level. As for minimum chlorophyll fluorescence (F0) no significant difference was observed between the two levels of irrigation. Also drought stress significantly increased chlorophyll content at 5% probability level. Both factors (levels of solution and different irrigation levels) affected relative water content (RWC) at 1% probability level. The highest correlation was observed between white sugar yield and photochemical capacity of photosystem 2 (FV/FM). In this study interactive effect was not found to be significant.

Drought stress is considered as the most important environmental abiotic stress, affecting grain yield of crop plants especially in arid and semi arid regions. Increasing and utilization of the genetic diversity can be a useful strategy in breeding for drought resistance. In this study, twenty Iranian durum wheat landraces along with two check cultivars were evaluated in a randomized complete block design with three replications, under stress and under non-stress conditions, in 2005 in Karaj, Tehran. Lines showed significant differences for most of the traits examined in either stress or non-stress conditions except for the number of leaves. The highest reduction, in stress condition, was observed for spike weight, grain yield and as well as for the leaf relative water content. Correlation analysis indicated that in both conditions, yield components including number of spiklets per spike, seed weight, number of kernels per spike and spike weight as well as biological yield, harvest index and peduncle length, exhibited the highest positive correlation with grain yield. The stepwise regression showed that harvest index, biological yield, number of spiklets per spike and days to flowering could be used as desirable criteria for yield improvement under non-stress condition, whereas spike weight, number of grains per spike, harvest index and biological yield could be considered as useful criteria under stress conditions. Principle component analysis and biplot graph showed that Stress Tolerance Index (STI), Geometric Mean Productivity (GMP), Harmonic Mean (Harm), and Mean Productivity (MP) might represent the best indices for drought resistance selection. Based upon bi-plot graph, lines 9, 15 and 21 were found to be the most resistant, while lines 5, 6, 4 and 8, the most susceptible.

A field experiment was conducted to assess the effect of lowered doses of herbicides on the control of perennial ryegrass (Lolium prenne L.) when growing in competition with wheat. The experimental design was a split plot factorial one with four replications.Main plots consisted of cropping system namely: Lolium pure stand vs. that grown with wheat. Sub plots consisted of two herbicides Clodinafop- propargyl and Mesosulfuron-Methyl (as two levels of the factor a) and 5 herbicide doses (0, %12.5, %25, %50 and 100 rate of recommended dose) in a factorial arrangement. Wheat yield was separately subjected to ANOVA in a randomized complete block design. Weed biomass in pure stand weed plots and in the presence of wheat exhibited significant differences.Clodinafop- propargyl did not totally controlLoilium. Conversely, a full and a half full rate of Atlantis rendered a higher control of ryegrass and yielded significantly more wheat. By use of herbicide at more than 50% of full recommended dose, no increase occurred in wheat yield. As a whole spraying the field at 240 g/lit of Clodinafoppropargyl and 400 g/kg of Mesosulfuron-Methyl, field recommended rate, did not perfectly control the weed, indicating that it needs more investigation to optimize the herbicide dose for future recommendations.

To evaluate the effect of cover crops, tillage systems and nitrogen (N) application rates on yield of forage sorghum (cv. KFs3), a factorial–spilt plot arrangement based on randomized complete block design with four replications was carried out at the Research Farms College of Agriculture and Natural Resources, University of Tehran, Karaj, during the growing seasons of years 2005 and 2006. Combinations of tillage systems, namely: either reduced (Disc) or conventional (Moldboard Plow+Disc) and N rates (0, 75 and 150 Kg.ha-1) were assigned to main plots, while winter cover crops (rye, hairy vetch and fallow or no cover crop) allocated to subplots. In either of the years, the tillage system did not affect the yield quantity and quality of forage sorghum, but significant differences were observed for N rates and cover crop treatments in terms of forage sorghum yield. Forage yields increased with increasing N rates, and the maximum yields were obtained with the highest N rates per hectare. There were significant differences observed between cover crop treatments as compared to check, but no significant differences between rye and vetch cover crops were recorded.Combined analysis showed significant differences for N rates and cover crop treatments in such qualitative attributes as digestive dry matter, soluble carbohydrates, crude proteins and ash. The results showed that using cover crops with 150 Kg of N ha-1 accompanied by reduced tillage system are advisable for forage sorghum production in Karaj region.

Genotype evaluation and mega-environmental identification are among the most important objectives of multi-environmental trials. Although the measured yield is a combined result of effects of genotype (G), environment (E), and genotype by environment interaction (GE), only genotypes and GE interaction are relevant to genotype evaluation and mega-environmental identification. This study presents a GGE (ie, G+GE) biplot, which is constructed by the first two symmetrically scaled principal components (PC1 and PC2). The GGE biplot graphically displays G plus GE of a multienvironmental trial in a way that facilitates visual genotype evaluation and mega environmental identification. This strategy was employed to analyse winter canola (Brassica napus L.) multi-environmental trial data. The stabilities for yield of 24 canola genotypes were determined using replicated trials for two years and nine locations. The first two principal components (PC1 and PC2) of the SREG model accounted for 65% of the total GE interaction. There were six winning genotypes and three megaenvironments according to the SREG model and polygon view of biplot. According to the ideal-genotype biplot, genotype DP.94.8 was better than all the other genotypes and had the general adaptability for all the environments; it exhibited both high mean yield and high stability of performance across environments. The estimated relative yield of genotypes in Karaj revealed that genotype SLM046 yielded the highest in Karaj area.According to genotype+GE interaction sources of variations, the genotypes Olara, Consul and SLM046 were the most suitable varieties for the canola producing regions in Iran and had the specific adaptability for each and any of the environments. The results of this study should help in determining the test sites or environments for winter canola comparisons in Iran. Based on the obtained results, genotype Consul for Arak, genotype Olara for Shahrekord and genotype SLM046 for Isfahan, Eslamabad, Sanandaj, Zarghan, Zanjan, Karaj, and Hamadan were the ones proposed for cultivation.

Effects of Gibberellic Acid (GA) and Abscisic Acid (ABA) on dormant and after ripened wheat seed, Cultivar RL4137, were studied. The aim of the study was to evaluate the effects of seed after-ripening in comparison with Gibberellin application on breaking of seed dormancy. Moreover, the effect of Abscisic Acid on dormancy induction was also evaluated. Acid and alkaline posphatase activity of seed embryo in dormancy release and induction was studied. Six weeks of after-ripening increased germination percentage and reduced dormancy levels. A hundredTmol of GA increased germination percentage equivalent to six weeks of after-ripening. As for ABA treatments, only higher concentrations (200Tmol) of this hormone were effective on dormancy induction in after-ripened seed. Dormancy induction following ABA treatment was equivalent to the seed dormancy at the fourth week of after-ripening.After-ripening increased acid phosphatase activity up to the third week, however, GA did not affect the activity of this enzyme. Unlike acid phosphatase, after-ripening reduced alkaline phosphatase activity and similar to acid phosphatase no GA effect was detected on activity of this enzyme. ABA only had negative effect on acid phosphatase activity and did not affect alkalin phosphatase activity. The results of this study suggested that after-ripening and gibberellins breaks seed dormancy in different ways.Likewise, the ABA role in dormancy induction is through a control of acid phosphastase activity.

Drought stress is considered as one of the most important abiotic stresses which damages tobacco production in many countries including Iran. Thus, an investigation of drought tolerant genotypes is one of the most important goals in tobacco breeding projects in Iran. Towards this end, in the present investigation, 15 hybrids of tobacco including 10 Iranian and 5 international hybrids were evaluated in a RCBD with three replications in two different environments (water stress and normal irrigation) in the Tirtash and Rasht Tobacco Research Station in 2007, where some tolerant indices were studied. Based on the dry leaf yield potential (Yp) and yield stability (YS), some such quantitative criteria of drought resistance as: Mean Productivity (MP), Tolerance Index (TOL), Geometric Mean Productivity (GMP), Harmonic Mean (Harm), Stress Susceptibility Index (SSI) were figured out. High significant differences were observed among genotypes for all the indices as well as for potential vs. stress yields, indicating the existence of genetic variation and possibility of selection for drought resistance.Correlation analysis among indices, along with potential and stress dry leaf yield indicated that MP, GMP and STI comprised the most suitable criteria for screening tobacco genotypes. Multivariate analysis biplot indicated that k394xNC89, NC55 and NC89xCoker347 in Tirtash and CC27 and Coker 254xVE1 in Rasht yielded the highest, and were tolerant to drought stress. Distribution of the genotypes in the biplot space indicated the presence of genetic diversity among the genotypes for drought stress.

Each gene consists of three major parts namely promoter, the main body of the gene and terminator. Without the promoter, there whould be no gene expression. In general, promoter is specific for each gene, and leads to the regulation of the final product of the gene. One of the most common promoters employed by plant genetic engineer is CaMV35S. Although it is assumed that CaMV35S is a constitutive promoter, but some reports suggest that this promoter is not expressed in all tissues and cell types. In addition, full accessible information regarding the expression profile of this promoter in all cells, in different tissues, and at the initial stages of development is lacking.Considering the above mentioned limitations, it leads one to study in more detail the CaMV35Spromoter activity. For an analysis of the promoter activity, tobacco transgenic plants in which one of the interfering committed steps in their vitamin E biosynthesis had been inhibited through RNAi system were employed. Silencing of the gene involved in this interfering step resulted in reduced content of vitamin E in the transgenic plant as compared with the wild type. Since as a whole, vitamin E content will undergo reduction in transgenic plants, the vitamin’s content in such different tissues as leaves, root, flower organs, immature and mature seeds of tobacco transgenic vs. wild type plants was measured. The data recorded here demonstrate thatCaMV35S promoter has highly expressed activity in leaves and flower organ, moderate expression activity in roots and seeds, and while very lowly expressed in mature seeds.

A hydroponic experiment was conducted to evaluate the effects of salt stress on safflower genotypes under greenhouse conditions. The experiment was arranged as a factorial one based upon a completely randomized design with three replications. Five safflower genotypes (Arak2811, Nebraska10, SOD25, CA116, and CA128), and four salinity treatments (0, 0.3, 0.5, and 0.7 percent of NaCl) were employed as experimental factors. Salinity exerted considerable effect on the growth parameters. Plant height, shoot and root dry weight, the concentrations of Na, K, Ca, and Mg in leaves and roots, and also the concentration of proline in leaves were meseared in samples obtained from the plants harvested one month after being exposed to salinity. Salinity decreased plant height, shoot and root dry weight, as well as the concentration of K, Ca, and Mg in leaves and roots. Howevere, the concentration of Na in shoots and roots increased under saline conditions. There was a significant interaction between the levels of salinity and genotypes for shoot dry weight. Among tested genotypes CA128 showed to be more salt tolerant in terms of dry matter accumulation regarding all levels of salinity. The effect of salinity on shoot/ root ratio was not significant. The concentration of proline in the leaves increased in saline treatments but the differences between genotypes and the interactions between the levels of salinity and genotypes were not significant as far as the concentration of proline in the leaves is concerned. The ratio of Na/K in the leaves and roots was higher in the plants subjected to salt stress. The differences between genotypes were significant regarding this ratio. Among the tested genotypes the ratio of Na/ K in the leaves was highest for Nebraska10. Howevere, the interaction between the levels of salinity and genotypes was significant for the ratio of Na/ K in plant tissues.The results of this experiment showed that salinity can significantly affect the growth of safflower and the responses of safflower genotypes to salinity might be different in terms of dry matter accumulation and in terms of ionic relations.

Many QTLs related to agronomic triats have been registered in soybean (Glycine max) by different research groups during the last decade. Due to the interaction effects of QTLs, environmental and genetic backgrounds on the emergence of QTLs and also to confirm the previous results as well as to identify new QTLs, further studies are still required. In order to map QTL which control some agronomic triats, a population consisting of 140 F2 plants, derived from a cross between Williams-82xRGR-JAP, were genetypically assessed by employing 17 SSR and 70 AFLP markers. Ultimately, based on the expected mendelian segregation, 12 SSR and 50 AFLP markers were used for the genetic map along with QTL mapping. Phenotypic evaluation was carried out on 140 F2:3 families for 21 traits. In the end, the linkage map consisting of 13 linkage groups were perpared which covered the genetic map of 733 cM in length. QTL mapping was done using composite interval mapping method which collectively detected 13 QTLs for 10 traits. A major QTL with pleiotropic effects was detected between the two markers Satt-365 and Satt-489 in LG- U9. Results of previous studies confirmed the existence of this QTL. A QTL responsible for reproductive duration and as well for the no. of branches (close to Satt-231 marker in LG-U4) was also detected.

Eight forage sorghum cultivars (Sweet jumbo, Nectar, Chopper, Pacific BMR, Speed feed, KFS1, KFS2 and KFS3) were assessed to determine the most suitable traits carrying cultivar, through a randomized complete block design with four replications during 2003-2005. Ammonium phosphate (basd on P2O5) was applied at 115 Kg/ha and 183 Kg/ha of nitrogen (urea-based) at four application times. Six traits, namely green fodder, dry matter, protein yield, plant hieght, stem diameter and tiller number were assessed for each cut. Harvesting was conducted from a 7.8 m2 area. Three years’data were analysed in a combined analysis and the means compared through Duncan Multi Rang Test (DMRT). Combined analysis of variance showed significant differences among cultivars, years, and cultivar x year interactions. A comparsion of means indicated that, Nectar and Chopper cvs. produced the highest vs. the lowest green fodder of 186.8 and 137.2 t/ha, respectively. They did not significantly differe from some other cultivars. As for dry matter yield, the cultivars Sweet jumbo, Nectar, KFS3 and KFS2 with mean yields of 39.21, 39.11, 37.54 & 37.41 t/ha, respectively ranked the top. Sweet jumbo produced the highest tiller number per plant (3.69) while Nectar yielded the highest protein (3.14 t/ha). The highest plant height (224.2 cm) and stem diameter (17.99 mm) belonged to Speed feed and KFS2, respectively. Among the cultivars, Chopper produced the lowest dry matter (32.95 t/ha), protein yield (2.62 t/ha), plant height (181.7 cm) and tiller number per plant (2.11), however the lowest stem diameter (12.33 mm), belonged to Speed feed.

To investigate the changes in yield and yield components of dry land wheat (Triticum aestivum L. cv Agosta), under the influence of residue and nitrogen levels and different tillage practices, a field experiment was conducted during the 2006-2007 growing season, in the Agricultural Research Station of the College of Agriculture, Shiraz University, Iran. The experiment was designed as a split-split one based on completely randomized blocks with 4 replicates. The treatments were comprised of three tillage practices (T1: moldboard plow+two perpendicular passes of disk harrow, T2: chisel plow+two perpendicular passis of disk harrow, T3: two perpendicular passes of disk harrow) as main plot, three levels of residue left on the soil surface (0, 50 & 100 % by weight of past year wheat residue, R1, R2 & R3, respectively) as sub-plot and three nitrogen levels (0, 100 & 200 Kg N/ha N1, N2 & N3, respectively) from urea source as sub-sub plot. The results indicated that nitrogen application significantly increased wheat yield and yield components. Main effect of residue on seed yield and 1000 seed weight was significant, leaving the residue on soil surface was associated with increased 1000 seed weight as well as grain yield. Tillage practices also affected seed yield significantly. The highest level of seed yield was achieved at T3 (99.01 g/m2). Among the grain yield components, 1000 grain weight and grain number per spike were affected by interaction of RxN with the highest 1000 seed weight and grains per spike obtained from N3xR3 treatment. Overall, this research revealed that under similar agro-climatic conditions, leaving plant residue on soil surface along with N application could result in higher yield in dry land wheat through improved traits of 1000 grain weight and number of grains per spike.