Iranian Journal of Field Crop Science
Year:2008 | Volume:39 | Issue:1|Papers Count:26

A field experiment was conducted during 2003-4, 2004-5 cropping seasons evalute the effects of plant density on growth and yield of different rapeseed cultivars. The Study was carried out at Ramin Agriculture and Natural Resources University (35 Km from northeast of Ahwaz). The experiment was in the form of split plots' based upon a complete randomized block design of four replications. Main plots consisted of 3 cultivars (Hayola 308, PF7045 and Option 501) while subplots of 4 plant densities (50, 70, 90 and 110 plants/m2). Results showed that increase in grain yield (4.20 t/ha) was obtained for Hayola 308 with 110 plants/m2. Option 501 resulted in the least grain yield at 50 plants/m2 (2.55 t/ha). Among yield components, number of pods/m2 and number of kernels per pod were the most affected by plant density and cultivar. The number of pods/m2 increased with increasing plant density, while the number of kernels per pod was decreased. A decreasing trend was observed in 1000-kernel weight up to 90 plants/m2. Considering the advantages of uniform distribution of plants and the adaption of Hayloa to a plant density of 90 plants/m2 it might be appropriate to use this formula for planting rapeseed under conditions similar to the ones in this experiment.

Residue management has a direct impact on soil physical and chemical characteristics which in turn have identical effects on sustainability of crop production in agroecosystems. The effects of wheat residual management practices (burning, plowing under and removal) on soil physical and chemical characteristics were investigated in this research. Treatments were compared in a complete block design of four replications. The measured traits were: soil nitrogen, phosphorus, potassium, calcium, zinc and magnesium, soil organic matter, pH, bulk density as well as C/N. Soil nitrogen content in residue burning treatment decreased as compared to control, while potassium and phosphorus increased significantly. In residue plowing treatment soil nitrogsn significantly decreased because of a higher C/N ratio as compared to control. However, soil organic matter increased with an increase in C/N ratio. Wheat residue management affected soil pH and organic matter but it did not affect soil bulk density. The ploughing of residue significantly reduced the grain yield of sunflower. Burning wheat residue increased the grain yield of the succeeding crop; however, grain yield was not significantly different from those in other residue management practices.

Hybrid rice varieties are potentially higher yielding than the best inbred varieties and perform better under adverse conditions of drought and salinity. One of the major impediments for seed production of hybrid rice is incomplete panicle exsertion in the cytoplasmic male sterile lines. The unexserted spikelets which are left inside the flag leaf sheath remain unfertile. This research was focused on studying the related traits as well as analyzing the effect of gibberellic acid on them. Examination of the panicle, peduncle and flag leaf sheath length from two days before heading to five days after heading showed that the peduncle length is the only variable factor in this stage. Investigating peduncle elongation process in A (male sterile) and B (maintainer) lines revealed that peduncle elongation is much slower in A line following heading. Gibberellic acid role on peduncle elongation was confirmed by showing its significant effect on detached peduncles. Gibberellic acid spray had no significant effect on panicle and flag leaf sheath but increased peduncle length. The ultimate peduncle length in A line sprayed with GA3 is almost equal to B line without GA3 spray, carrying all the florets out of the flag leaf sheath. Studying the peduncle elongation pattern in eui-10, an elongated uppermost internode IR64 mutant, showed that peduncle elongation rate is much higher than IR64 such that after heading, the eventual peduncle length is almost doubled. This trait can be employed in breeding programs for hybrid rice to improve the performance of heading in male sterile cultivars.

To evaluate the growth regulatory effect of chlormequat chloride (CCC) under drought stress conditions on three barley cultivars, a field study was conducted under Badjgah agro climatic conditions (altitude 1810 m, longitude 52o46’, and latitude 29o50’) during 2003-2004 growing season. A randomized complete block based split- split plot of four replications was employed with two moisture levels (well watered and drought stress during the post anthesis period) as main plots, chlormequat chloride treatment placed in sub plots (control and 1370 g a.i. ha-1 at lemma primordium stage) and 3 barley cultivars (Reyhaneh, Karoon and Valfajr) as sub-sub plots. The results indicated that drought stress decreased the grain yield, biological yield and harvest index of barley cultivars. The effect of drought stress on yield components, except for the number of grains per spike, was significant. CCC enhanced grain yield under well watered conditions, however, under drought stress conditions it decreased the grain yield significantly. The number of spikes m-2 was increased in CCC-treated plants. Dry weight and leaf area decreased under drought stress conditions. Green leaf area and dry weight of CCC-treated plants were greater during post anthesis period. Although a deep understanding of the effect of CCC on grain yield under drought stress conditions needs more research and for longer periods, it became evident that the timely use of CCC in irrigated barley farms could result in to an increased grain yield.

High molecular weight (HMW) subunits of wheat glutenin are generally considered as playing a key role in gluten formation and structure, as well as to be closely related to wheat quality. The endosperm storage proteins of 80 synthetic lines and wheat cultivars (Triticum aestivum) were fractionated through sodium dodecyl sulfate polyacrylamide gel electrophoresis to determine their high-molecular-weight (HMW) glutenin subunit composition and their relationship with bread-making quality. Twenty six high-molecular-weight (HMW) glutenin subunit compositions including fifteen different alleles were found of which 2* allele of Glu-A1, 7+8 allele of Glu-B1 loci and 5+10 of Glu-D1 were of the highest frequency. The 2***+12 subunit, first reported from Pakistan, was observed in 7 lines. SDS sedimentation test was performed to study the effects of HMW Glutenin subunits on bread-making quality. The results of ANOVA showed that 2*, 5+10 and 17+18 alleles of Glu-A1, Glu-D1 and Glu-B1, had the most positive effects while Null allele (43.75%) had the most negative effects on SDS sedimentation trait. Stepwise regression analysis revealed that the subunits of 5+10, 17+18 and 7+8 can justify 31.4% of variation in SDS sedimentation.

Seeds of most crops including those of range plants follow orthodox behavior. However, these seeds undergo aging even under favorable conditions, so that decreased viability and vigor related parameters are the main characteristics of deteriorated seeds. The effects of hormonal priming with auxin, cytokinin, gibberellin and abscisic acid at 0, 50, 100 and 150 ppm on physiological quality of tall wheat grass deteriorated seeds were evaluated (at Natural Resources Gene Bank of Iran in Research Institute of Forests and Rangelands). Germination percentage, seedling dry matter and number of seminal roots were not affected by drought stress (-0.5 MPa). However, stress condition decreased the rate of germination, vigor, seedling fresh weight, length of root, shoot and seedling, and increased Mean Germination Time (MGT) as well as root-shoot ratio. Priming improved germination percentage under drought stress. Germination percentage and rate of germination of primed seeds were higher than those in non-primed ones under drought conditions. Gibberellin and cytokinin induced more rapid germination in non-drought condition, while auxin decreased the rate of germination. Priming the seeds with gibberellin, abscisic acid and cytokinin at 50 and 100 ppm decreased and increased MGT in non-drought and drought conditions respectively. Seeds primed with gibberellin (100ppm) have the highest vigor index under non-drought condition, but in drought condition, cytokinin (50ppm) produced the highest vigor index. Auxin decreased root length; meanwhile, increased the number of seminal roots. All the priming treatments decreased root-shoot ratio. According to the results, it could be suggested that the enhancement of physiological quality of deteriorated seeds in tall wheat grass can be obtained through hormonal priming. Seed priming by either gibberellin (100ppm) and cytokinin (50ppm) or ABA (50ppm) would be helpful for improvement of seed performance under drought and drought conditions respectively.

Production of transgenic cotton (Gossypium hirsutum L.) was studied utilizing Agrobacterium-mediated strain LBA4404 and pBI121 plasmid. This plasmid contains gus as a reporter gene driven by the CaMV35S promoter and nptII gene driven by NOS as selection marker. In this study, the inheritance of gus gene was evaluated using selective media, PCR and GUS staining in the second genertaion (T1) of transgenic cotton obtained from those plants in which the expression of gus gene was confirmed in different tissues (pollen and fiber). Seed samples from transgenic lines (T0) along with non transgenic control seeds were employed. The X2 test indicated that the inheritance of gus gene in A3, A4 and A7 lines follows Mendilian ratio for single gene segregation (3:1). PCR amplification was carried out to test the presence of nptII gene in the second generation. The results revealed the presence of nptII gene in all the GUS positive transgenic plants except in one. The results confirmed the stability of gus gene in the second generation.

In order to determine the relationship between the variables grain yield and biological yield and some important agronomic traits, and to find the direct and indirect effects of important agronomic traits on both grain and biological yields, 364 soybean genotypes (3 planting dates) were studied. The study was based on a design augmented with 3 checks and 6 blocks implemented, in Seed and Plant Improvement Institute, karaj, Iran, during 2003-04 growing season. The results of simple correlation indicated that the biomass, number of seeds as well as number of pods per plant were in a high correlation with seed yield per plant for all the planting dates. Also seed yield, number of nodes in main stem at the beginning of maturity stage, number of seeds as well as number of pods per plant were in a high correlation with biological yield. The results of stepwise regression and path analysis showed that number of seeds per plant and 100 seed weight exerted the greatest positive effects on both grain yield and biological yield for all planting dates. The results therefore suggest that the number of seeds per plant and 100 seed weight be can used as selection criteria in soybean grain and biological yield improvement.

In order to study the effects of post - anthesis heat stress on source of six wheat genotypes (Vee/Nac, Chamran, S79-10, Dez, Fong and Kaveer), two separate field experiments were conducted as delayed as against optimum sowing dates in Ahvaz coditions.Plants in delayed sowing date experienced heat stress at post-anthesis growth stage. As study of grain yield indicated that the highest and the lowest grain yields in optimum conditions belonged to Chamran and Fong genotypes, respectively. The highest and the lowest grain yields in stress conditions were obtained for Vee/Nac and S79-10 genotypes, respectively. The highest and the lowest stress susceptibility index (SSI) for grain yield and also the highest and the lowest reduction in grain yields occurred for S79-10 and Fong genotypes, respectively. Chamran and Kaveer genotypes expressed the highest and the lowest stress tolerance indexes (STI) for grain yield. Mean of source restriction in optimum and heat stress conditions were 8.3% and 24%. Mean of source restriction aggravation in late heat stress was 29%. Higher source limitation in a late maturity genotype such as S79-10 was related to delay in anthesis and a coincidence of grain growth period with heat stress. In such short-season genotypes as Fong and Vee/Nac with early anthesis, grain growth period was ahead of heat domineering conditions. Indeed the lowest source restriction along with the lowest grain yield reduction were recorded in these latest mentioned genotypes.

To investigate the effect of supplemental irrigation and nitrogen fertilizer on kernel weight, test weight and wheat grain yield under dryland conditions, a two-year field experiment was conducted in the research farm of College of Agriculture, Shiraz University during 2004-2005. Five irrigation regime including dryland conditions, irrigation at stem elongation, booting, flowering and grain filling constituted the main plots and two cultivars of Agosta and Fin-15 formed the subplots and while three levels of nitrogen including zero, 40 and 80 kgha-1 making the sub sub plots. The results indicated that in either of the years, the highest grain weight and test weight were obtained from irrigation at grain filling stage. Also the highest mean grain weight as well as test weight were obtained from 80 Kgha-1 nitrogen treatments. The results of this research also showed a strong correlation of mean grain weight and test weight with the amounts of nitrogen and water applied at supplemental irrigation treatments. The highest grain yield in both years was obtained from supplemental irrigation at stem elongation stage. The supplemental irrigations in 2004 and 2005 lead to an increase in the grain yield by 200 and 221 percent respectively. Also the highest grain yield was harvested from 80 Kgha-1 nitrogen treatment at all supplemental irrigation treatments. Thus, it can be concluded that supplemental irrigation at sensitive growth stages could significantly affect grain yield in rain-fed wheat, and a supply of adequate water and nitrogen at the appropriate growth stages could improve grain quality and increase yield in rain-fed wheat.

To cope with cold stress, winter cereals regulate their development through adaptive mechanisms such as vernalization requirement. Eight wheat and four barley cultivars were planted to determine the relationship between vernalization fulfilment and expression of cold tolerance under both field and controlled conditions. Cultivars were planted at Maragheh and Karaj Agricultural Research Stations in Iran. Plants were grown at 4oC for vernalization periods from 7 to 98 days under controlled conditions. Cold tolerance, as measured by LT50, and vernalization requirement, as estimated from final leaf number (FLN), were determined during the vernalization periods. In cold region of Maragheh, the FLN measurements indicated that vernalization requirement was achieved between 11 to 12 weeks after planting for Noorstar and about 8 to 9 weeks for either of Azar 2 and Sardari winter wheat cultivars. Koohdasht spring wheat did not need to undergo the vernalization requirement. The minimum FLN for Dobrynia winter barley was observed about 8 weeks. Rihane-03 and Dicktoo barley proved to be of no vernalization requirements. In moderately cold area of Karaj, the vernalization saturation of Noorstar, Shahryar and Alvand winter wheat was achieved after about 15, 6 and 4 weeks, respectively. Kavir spring wheat needed no vernalization requirement. Under controlled conditions, the fulfillment of vernalization saturation was observed between 28 and 35 days for Azar 2, about 28 days for either of Sardari and Shahryar, and 21 days for Alvand wheat cultivars. The FLN of spring wheat (Kohdasht, Kavir and Zagros) did not change indicating that these cultivars did not need to undergo vernalization requirements. Similar to field conditions, Rihane-03 and Dicktoo spring barley were of no vernalization requirements, while Kold and Dobrynia winter barley cultivars met their vernalization requirements after between 28 to 35 days of vernlization treatment. Noorstar acclimated to a lower temperature reached its maximum cold tolerance (LT50=-21oC) at about the same time as vernalization fulfilment occurred (42-49 d). Under field conditions at Karaj, Noorstar reached the same level of LT50, which was obtained under controlled conditions, while Azar 2 reached LT50 of -10oC at the vernalization saturation point. A similarity observed between vernalization in controlled conditions and that in field conditions indicates that fact that a fulfilment of vernalization is a turning point in cold resistence after which the resistance of plant to cold diminishes.

Field experiments were conducted to determine the influence of single and multispecies competition of common cocklebur (Xanthium strumarium L.) and jimsonweed (Datura stramonium L.) on corn yield and further the competitive abilities of these weeds. Common cocklebur and jimsonweed were established at selected densities within 15 cm on either side of the corn row. Common cocklebur and jimsonweed seeds were sown concurrently with corn. Corn yield losses in the conditions of single and multispecies weed competition were estimated from empirical equations based on the Cousens (1985) hyperbolic crop yield model. The results revealed that common cocklebur was more competitive than jimsonweed across all situations. In the mixed weed population plots including jimsonweed, common cocklebur and corn, while common cocklebur was assigned a competitive index of 1 on a scale from 0 to 1, the competitive ability of jimson-weed was recorded as 0.25 of common cocklebur. In the case of single weed population plots, one common cocklebur plant had 1.40 times a higher ability to reduce corn seed production as compared to jimsonweed. The results of this study, suggest that different weeds competition coefficients must be estimated from mixed weed population experiments.

To evaluate the effect of intercropping of sorghum and alfalfa on forage yield and on weed biomass production, different proportions of sorghum and alfalfa intercropping system comprised of 50% - 50%, 25% - 75% and 75% - 25%, along with sole cultures of sorghum, and of alfalfa were arranged as split plots in time, while a complete plot design with three replications being used to analyze the data. The experiment ran for three years during which no weed control measure applied. Alfalfa 25% - sorghum 75% was the highest forage producing treatment across the three years of the experiment while during the second year of the experiment alfalfa sole culture produced significantly more forage as compared to either of the intercropped treatments and sorghum sole culture, These in turn being followed by alfalfa 75% - sorghum 25% intercropping treatments. Sorghum sole culture was the least forage producing treatment across all the experimental period (three years). In the first year of the experiment, weed populations dominated alfalfa sole culture and other treatments with a higher proportion of alfalfa in the intercropping system. As the proportion of sorghum in intercropping system increased, the population of weed significantly declined. The population of weed followed a declining trend as the period of the experiment proceeded to the second and the third year in treatments with a higher proportion of alfalfa. The biomass of weeds in the second year of the experiment in the higher proportion of sorghum (>50% sorghum) treatments was highest at the first harvest. However, there was a significant declining trend observed at the forth and fifth harvests.

Poor wheat stand establishment is a major cause of yield loss, particularly in rainfed and poorly irrigated environments. Seeds of eight wheat cultivars (Triticum aestivum L.) including irrigated and rainfed varieties, belonging to three different climates of Iran (Hamedan as cold, Karaj as temperate and Sarpolzohab as warm climates) were primed using osmoprimig treatments through use of Urea, NaCl and PEG6000 as well as hydropriming treatments through tap and distilled water. In each climate while employing the related cultivars, a separate experiment was conducted using a split plot factorial in a randomized complete block design of three replications. Main plots were representatives of two sowing dates (timely, and late), while subplots included combinations of cultivar and priming treatments. Results showed that Urea and PEG osmopriming treatments as well as tap water hydropriming treatments caused an increase in emergence rate (both two sowing dates) in all rainfed cultivars of all climates as well as in Alvand irrigated cultivar of cold climate (Hamedan) zone. In addition, NaCl and Urea osmopriming increased flowering speed in first sowing date of Azar2 (rainfed cultivar of Hamedan) and Chenab (rainfed cultivar of Sarpolzohab) respectively. In rainfed cultivars of cold climate zones, PEG and Urea osmopriming significantly increased leaf area index. Number of spikes per unit area was the most important factor among yield components that was significantly increased by osmopriming treatments in Hamedan cultivars (both irrigated and rainfed cultivars) as well as in Karaj rainfed cultivar and for both sowing dates. This resulted in an increase in yield. Meanwhile harvest index was not affected by priming treatments. It seems that the desired effects of osmopriming would be on the increase in the presence of such environmental growth limiting factors as low temperatures and water deficit.

In order to study the genetic diversity as well as the relationships between seed yield and some morphological traits in common white bean, 500 accessions were evaluated in the experimental field of National Plant Gene Bank of Iran in 2004 in an augment design of three control varieties. Traits were evaluated according to the instruction of IPGRI. Results of descriptive statistics indicated that number of seeds per plant, seed yield per plant, number of pods per plant, plant height, number of nodes in the main stem, seed shape and growth type vaied considerably. The results of simple correlation, multiple regression and path analysis indicated that the number of pods per plant, 100 seed weight and number of seeds per plant had the greatest effect on seed yield per plant, and therefore were introduced as yield components. In principal component analysis, 6 principal components explained approximately 82.5 percent of the total variance.

Secale cereale is a nosious, problematic weed of wheat fields in Iran. For evaluation of the yield and yield components of bread wheat (Triticum aestivum L.) cultivars in the presence of rye an experiment was established in a randomized compelet block design with factorial arrangment of treatments in Meshkindasht and Varamin during 2002-2003 growin season. Experimental factors were wheat cultivars (Azadi, Mahdavi, Roshan, Tabasi, Pishtaz, Shiraz, Karaj2 and Nicknejad) and rye platation (0, 120 plants/m2). Results showed that rye plantation resulted in reduced yield and yield components of bread wheat. Grain yield loss varied from 7.32 to 44.82% and biological yield loss from 9.62 to 37.15% among cultivars at the two different locations.

As regards the kind of use and production of biomass, lettuce plant has a potential to be used as a bioreactor for producing recombinant proteins as well as edible vaccines. For this propose optimized tissue culture as well as gene transformation of Lactuca sativa are needed. Seeds of 5 cultivars namely TN-96-35, TN-96-36, TN-96-39, TN-96-41, TN-96-53, and TN-96- 54 were disinfected by being soaked in a solution of 2.5% sodium hypochlorite containing 0.1% Tween 20 for 25 minutes. After being rinsed three times with sterile distilled water, the seeds were made to germinate on filter paper in petri dishes with sterile distilled water in them. The cultures were continuously exposed to white fluorescent light at a constant temperature of 25oC, for a minimum of 16 hours. When aseptically germinated seedlings were 48 to 72 hours old, cotyledons were excised near the cotiledonary node, and cut into 6 to 8 pieces to increase the wound needed by the explants for an initiation of callus growth. Explants were cultured on MS medium supplemented with different levels of naphthaleneacetic acid [NAA] (0.02, 0.05, 0.1 mg/l) and benzyladenine [BA] (0.1, 0.2, 0.4 mg/l). Two lettuce cultivars (TN-96-39, TN-96-41), showed the best callus production, embryogenesis, regeneration and proliferation. The best growth regulators for callus production and embryogenesis were 0.05 mg/l [NAA] and 0.2 mg/l [BA]. The most suitable growth regulator for direct regeneration as well as proliferation were 0.05 mg/l NAA, and 0.4 mg/l BA. To produce roots, shoots were transferred to MS media contaning 0.2, mg/l NAA. Plantlets of robuts roots were then planted in pots to produce seeds.

Wheat crop grown under post anthesis drought stress condition may need a high level of stem reserve for grain filling. For an understanding of the genotypic variation of the traits stem reserves in wheat under drought stress conditions, 20 winter wheat genotypes were evaluated under both post-anthesis drought stress and normal conditions in Ardabil Agricultural Research Station in two successive growing seasons 2000-2002 using a Randomized Complete Block Design with three replications. The results showed that there were significant differences among the genotypes for stem reserve under either normal or post anthesis drought stress conditions. Post-anthesis drought stress did not affect kernel number per spike. The rate of dry matter accumulation in kernels considerably decreased by water deficit. Dry weight of vegetative organs decreased during grain filling period under either of the stress and normal conditions. But, the rate of translocated dry matter was much higher in genotypes 14, 15, 16, 18, 19 and 20 under drought stress conditions. On thousand GW and weight of kernels per spike were more severely reduced as due to water deficit. The significantly positive correlation of grain yield with remobilization of dry matter, harvest index as well as with stress tolerance index (STI) along with significantly negative correlation of grain yield with drought susceptibility index (SSI) revealed the fact that selection must be exercised for high harvest index, remobilization of dry matter and STI in a more effectively meeting of stress conditions.

To evaluate the reaction of some wheat advanced lines and cultivars to yellow rust at seedling stage, seeds of 200 accessions were planted in 5cm diameter pots (4-6 seeds per pot) in greenhouse. The seedlings were inoculated with fresh harvested urediniospores of two different races of Puccinia striiformis f.sp. tritici (134E134A+ from Karaj and 134E142A+ from Maragheh, Iran) when the first seedling leaves were fully expanded. Inoculated plants were placed inside a small plastic covered cage and kept at 10oC and 90% RH in the darkness for 48 hrs, and then transferred into a greenhouse of standard conditions (16 hours of light at 15oC and 8 hours of darkness at 10oC). The reaction of each line/cultivar was evaluated using McNeal et al., (1971) scale 15-17 days after inoculation. The results showed that 49% of wheat lines/cultivars were susceptible (infection types 7-9), 39% completely resistant (infection types 0-2), and 7% incompletely resistant (infection types 3-6) to race 134E134A+. Moreover 55%, 30%, and 9% of the accessions were respectively susceptible, completely resistant, and incompletely resistant to race 134E142A+. In addition, 41.5%, 24.5%, and 1% of the accessions were susceptible, completely resistant, and incompletely resistant to either one of the races respectively. High frequency of genotypes with susceptibility (7-9 reactions) indicates that most entries are in possession of no seedling resistance genes or have genes that yellow rust pathotypes are virulent to (Yr2, Yr6, Yr7, Yr9, YrA and YrND). Resistance reaction type genotypes are in possession of at least one seedling resistance gene to which yellow rust pathotypes are not virulent. According to the results, cultivation of lines/cultivars with resistance responses can be recommended for the areas where these races or similar ones are prevailing. Moreover some accessions with susceptibility reaction at their seedling stage may possess the ability to develop resistance at their later higher field developmental stages.

Forage species in mixtures are extensively grown worldwide nowadays, particularly as a step towards sustainable agriculture, however, information on this topic is scanty in our country. Thus a 2-year (2001-2003) field experiment was conducted to determine the forage yield, botanical composition, as well as competition of some forage grasses and legumes as mono and dual cultures combinations at Kushkak Agricultural Experiment Center, Shiraz University. The treatments were alfalfa (Medicago sativa L.), red clover (Trofolium pratense L.), orchardgrass (Dactylis glomerata L.), smooth bromegrass (Bromus inemis L.), and tall fescue (Festuca arundiacea Screb.) as monoculture and forage legumes along with grasses as dual cultures. Results showed that alfalfa monoculture and its dual culture with grasses had the highest total dry matter yields with significant differences as compared with red clover and its binary combinations. The forage yields were significantly higher during the 2nd than the 1st year. The highest total dry matter yield of alfalfa together with its binary combinations belonged to alfalfa-tall fescue and alfalfa-smooth bromegrass combinations. The competition of red clover with grasses was less pronounced than that of alfalfa. Orchardgrass had a lower competitive ability in binary combinations in both years, unlikely being able to compete with alfalfa; however, it produced a higher proportion of forage yield with red clover during the 2nd year. Alfalfa was a dominant species in alfalfa-smooth bromegrass combination and smooth bromegrass was a dominant species in red clover- smooth bromegrass combination. Overall, alfalfa-smooth bromograss and alfalfa-tall fescue binary combinations produced higher forage total dry matter in either one of the experimental years and it seems that they can endure a longer endurance in the region.

This research was conducted to study the effect of yield, and its components on seed oil content and its quality. Twenty soybean varieties were employed in a randomized complete block arrangement with three replications at the Agricultural Experiment Station, College of Agriculture, University of Tehran, Karaj, Iran. A total of 25 traits related to vegetative and reproductive growth, yield component and oil as well as fatty acid contents were analysied. In estimation of simple correlation between traits, oleic acid percentage was positively correlated with seed length with oil yield while negatively correlated with linoleic and linolenic acid contents (percentages). Linolenic acid showed negative correlation with plant yield and linoleic acid percentage but was positively correlated with palmitic acid percentage. In stepwise regression analysis, using oil yield as dependent variable, 3 variables entered into the regression model which accounted for 91% of oil yield variation. In path analysis, stearic acid percentage and number of pods/plant had high positive direct effects on oil yield. PCA resulted in six factors that accounted for 79.6% of total variation. Results of factor analysis suggested that seed size traits could be used as selection criteria in breeding programs to improve seed oleic acid percentage.