Iranian Journal of Field Crops Research
Year:2004 | Volume:1 | Issue:2|Papers Count:16

In order to have a successful breeding program, it is important to determine the genetic relationship among the traits. This study was conducted to investigate the relationship among agronomic traits in safflower at two moisture stress and non-stress conditions. In this study, 15 safflower genotypes were evaluated at two different moisture regimes, based upon depletion of 50% and 85% of soil moisture content. In each moisture regimes, a randomized complete block design with three replications was used. The phenotypic and genetic correlation coefficients revealed that in both irrigation regimes, number of seeds per head, plant height and days to maturity had a high positive correlation with both seed yield per plant and seed yield per plot, while the number of heads per plant was significantly and negatively correlated with seed yield per plant and seed yield per plot. The results of stepwise regression for seed yield per plant as a dependent variable indicated that in non-stress conditions, number of seeds per head, 100-seed weight, plant height and number of heads per plant were entered in the model, respectively and they contributed in 93% of the variation for seed yield per plant. In the stress conditions, the same traits, except the plant height entered in the model with the same sequence and they contributed in 94% of the variation for seed yield per plant. The results of path analysis for genetic correlation coefficients between each of seed yield per plant and seed yield per plot with their corresponding traits in the regression model showed that in both moisture regimes, the number of seeds per head had the highest direct and positive effect on seed yield per plant and seed yield per plot, but this direct effect reduced by its negative indirect effects via number of heads per plant and then 100-seed weight. The number of heads per plant in both stress and non-stress conditions had a positive direct effect on the seed yield per plant and seed yield per plot. However because it had a considerable negative indirect effect via number of seeds per head, it had a negative correlation coefficient with each of seed yield per plant and seed yield per plot. In general, the results of this study showed that in both moisture stress and non-stress conditions, the number of seeds per head can be considered as a good selection criterion to improve seed yield in breeding programs of safflower. Also, it seems that in non moisture-stress conditions, the tall and late-mature genotypes can produce more seed yield.

The importance of spatial distribution in sampling weed populations, modeling population dynamics, and long-term weed management has been particularly important for methods to describe and analyze the spatial and temporal distribution of weeds. In year 2002, in a field located at Mashhad, weeds were identified and counted at 171 points of a corn field (1 ha) based on a 7 (m) by 7 (m) grid in 0.15 m2 quadrates, 3 times within the season including prior to post emergence management, after post emergence management, and before harvest. Geostatistical techniques were used to analyze the spatial structure of weeds and dynamics of patches. Fifteen weed species were observed across the field. Semivariogram analysis indicated 3.5 to 236.5m as the range of influence (patch size) which depends on weed species and sampling time (stage of growth). The semivariogram analysis also indicated that 51 to 85 % of the variation of sample density was due to spatial dependence, which suggests that most of the species were patchy. Semivariogram parameters did not change significantly over time for field bindweed which indicated the relative stability patches of this weed. Barnyardgrass was not treated with herbicide, thus patches have rapidly spread. For other weed species, the range of influence decreased (patches were smaller), but spatial structure was more stable over time which results in consistent patch position. The maps also showed elongated patches (anisotropy) along the field which may be in response to direction of tillage, irrigation and all other management practices. The results of this study showed that spatial distribution monitoring allows prediction of weed behavior and thus can be a valuable tool for management decisions and increases our understanding of the dynamics of weed

To study the mechanisms of competition of barnyardgrass and redroot pigweed with dry bean, an additive experiment was conducted at farm of Ferdowsi University of Mashhad experimental station. The experiment was laid out in completely randomized block (CRB), with three replications. Treatments included three levels of redroot pigweed densities (4, 8, 12 plant/m2) and three levels of barnyardgrass (10, 20, 30 plant/m2) planted at constant density of dry bean (20 plant/m2) plus weed free check in each block. Results showed total dry matter (TDM), growth rate, height and bean leaf area of bean decreased significantly. In all above parameters, redroot pigweed was more effective on dry bean than barnyardgrass. Meanwhile, excluding the early season growth, redroot pigweed growth index curves exceed from bean. However, in barnyardgrass except the end of the season (bean physiologycal ripening period) growth index curves were lower than bean. Higher height and leaf position of redroot pigweed in mix canopy from early season resulted in being redroot pigweed more competitive for light than bean. However, barnyardgrass weakness in latter two parameters during growing season was the main reason for its weakness for light competition. Apparently, barnyardgrass imposed its competetive effects via partitioning the assimilates to roots wherease, redroot pigweed, imposed its competitive from roots and mainly foliages.

Response surface analysis was applied to data of seed germination rate and shoot length of three alfalfa cultivars (Hamadany, Gharay Yonjehe, Nik shahri) in relation to temperature and salt integrated conditions. Completely randomized factorial experiment with four replications on five levels of temperature (5, 10, 15, 20, 25oC) and 4 levels of sodium chloride salinity (control, 0.05, 0.1, 0.2 molar) was conducted. Response surface was developed for each cultivar using multiple-regression techniques (in such situation this procedure is best appropriate for quantitative factors). Results showed that partial regression coefficient for germination rate and shoot length equations in each cultivar were varied and so response surface were changed. Coefficients of the best equation from the response surface of each cultivar for each salt level through a series of temperatures were changed. In general, result showed that by increasing of salinity and temperature range, germination rate and shoot length were decreased. These comparisons form a statistically valid basis to select the most adapted cultivars and predict the best planting time at suitable temperature and salt stress condition.

Weed population of bean, corn, suger beet and fallow treatments were studied following three years of crop rotation of fallow- corn- winter barley in a completely randomized design arrangement with four treatments and four replications per treatment during 2002 growing season. The treatments under study were included of four following rotations: Fallow, corn, barley, corn., Fallow, corn, barley, bean., Fallow, corn, barley, sugerbeet., Fallow, corn, barley, fallow. Population density and species diversity of weed seedlings within quadrat mounted in each plot were studied four times during growing season for each rotation treatments. The results indicated that crop species indirectly influenced on weed population obtained from soil seed bank. Therefore, the average weed seedlings density presented within crop rotation treatments were significantly different from fallow treatment. The effect of crop on weed seedling germination, produced from seedbank indicated that using a crop following fallow, corn and barley resulted in reduction of weed seedling during growing season.

This study was conducted in J. Rock agricultural research station for two years, in order to study the effects of time, rate and application method of Zn fertilizer on yield, yield components and Zn uptake by two potato cultivars. Experimental factors were two potato cultivars (Agria and Marfona) and Zn application including three soil application rates (0, 30 and 60 kg/ha) and four foliar application (foliar application on early growing season, 50% of flowering, early growing season plus 50% of flowering and no foliar application). The Factorial experiments in randomized complete block design with three replication was used. Results in two years showed that the potato growth stages had no effect on treatments and growth stages including emergency, flowering, hilling and maturity were happened for all treatments in the same time. The Zn concentration in potato leaves was not affected by soil Zn application but foliar applications have significant effects on Zn concentration. It seems that soil characters such as high pH and low organic matter were the main causes of this results. Results also showed that treatments had no effect on tuber yield, but number of tuber was different in two cultivars and Marfona produced higher tuber number in comparison to Agria.

The effect of drought stress on nitrogen and SPAD reading of wheat (cv Falat) was studied in a complete randomized block design with 3 replications; in the green house. Five levels of drought stress (-0.3, -1, -3, -5 and -7 b) were used as treatments. Soil water curves were plotted using presser plate at a wide range of soil water potential. Water requirement for each treatment determined with weighing by day of each treatment. SPAD reading, nitrogen content, stomatal resistance and specific leaf weight (SLW) of flag leaf and two leaves under flag leaf were measured at anthesis stage. Results showed that with increasing drought stress SPAD reading, nitrogen content, stomatal resistance and SLW increased and there was a high relationship between drought stress and SPAD reading. It was concluded that SPAD reading is a good index of nonstomatal resistance for preduction water stress severity.

In order to study dry matter accumulation in different developmental stages and remobilization in bread wheat cultivars under water stress, a field experiment was conducted using a split plot design based on a complete randomized block design with 3 replications for two years (2000-2002) in Torogh Agricultural Research Station (Mashhad, Iran). Main plots were allocated to 7 levels of water stress treatments namely D1: full irrigation, D2: water stress from one leaf stage to double ridge (floral initiation), and in other treatments water stress and prevention of precipitation from D3: One leaf stage to double ridge, D4: double ridge stage to early stem elongation, D5: early stem elongation stage to emergence of flag leaf, D6: emergence of flag leaf stage to anthesis and D7: anthesis stage to late of grain filling (soft dough), respectively. Four bread wheat cultivars (Roshan, Ghods, Marvdasht and Chamran) were assigned to sub plots. Results of combined analysis showed that, biological yield, grain yield, spike weight at anthesis, harvest index, accumulation of dry matter in different developmental stages, amount of remobilized dry matter, remobilization efficiency, remobilization percentage, duration of grain filling and plant height was significantly (p<0.05) affected by water stress treatments. Biological and grain yield, accumulation of dry matter in different developmental stages, spike weight at anthesis, harvest index and plant height, was decreased due to water stress at stem elongation stage (D5). Water stress decreased dry matter and limited source before anthesis (D5 and D6), but after anthesis (D7) decreased amount of remobilized dry matter and remobilization efficiency about 261 mg/plant and %33.9 in comparison to D1 treatment, respectively. In severe water stress treatments (D5 and D7) remobilization percentage were increased in comparison to D1, D2 and D3 treatments. In addition, D7 treatment, affected canopy temperature depression (CTD). Plant height and amount of remobilized dry matter of Roshan was relatively high. Also, Chamran had relatively higher grain yield and remobilization percentage and was relatively early maturing.

Despite a long history of saffron production in Iran, which dates back thousands of years, research on this crop is still in its early stages, starting only seventy years ago and the last review on saffron research in Iran was published about 15 years ago. Due to increasing research activity on different aspects of saffron in the last decade, need for a comprehensive review was indispensable. Research on saffron, when started, was mostly focused on saffron cultivation, however, the present review shows that new topics such as genetics, tissue culture, processing and economic issues have gained more attention during recent years. This review attempts to catalog all published works in Farsi (Persian) including 14 books, 90 research reports, 62 master and PhD thesis, 66 papers and 134 presentations at national symposiums into four major areas namely; cultivation technology, processing, use and applications and economic issues. Number of accessible resources and as the percentage of total, in these four categories, are 180 (47.8%), 100 (26.6%), 57 (15.4%) and 39 (10.3%), respectively. Analysis of the published works in the past 70 years reveals that about 80% of the works have been published during the last 15 years. Directions for future works have been proposed based upon the past conclusions and the emerging needs.

Heavy metals are toxic to all microorganisms if present in high concentrations. The disposal of sewage sludge on agricultural land is considered as one of the most important sources of heavy metals contaminations with a long term detrimental effects. Therefore, examination of changes in the zinc tolerance of soil bacteria is an important issue. In this experiment, metal tolerance of 25 isolates of R. leguminosarum bv. Viciae was investigated with two different (Solid medium and Resin) methods. The results showed that some of isolates originated from contaminated soils had zinc tolerance and some others did not. The results also showed that the Resin method had a better sensitivity compared to solid media for evaluating the metal tolerance. Resin method is recommended when the difference in metal tolerance among isolates is subtle.

Seedbank to some extent is a reflection of weed population and It is the results of management from past to present. Crop rotation verifies the rotation of cultural practices. therfore, it may be considers as a basic factor to determine the density and diversity of weed communities. The object of this study was to investigate the diversity, density and distribution of weed seeds in three rotation systems including: wheat-sillage corn, fallow-chiekpea and fallow-cumin. The experiment was conducted during 2003 growing season. Fallow - cumin with 131.5 seed per kg of soil and wheat -sillage corn with 15.09 seeds per kg of soil showed the highest and lowest seedbank density, respectively. The Shannon diversity index was different in different rotations. Therefore, It may saggested that maniupulation in agroecosystems by human had significant effects on potential of various species presence. On the other hand, seeds of different weed species showed patchiness distribution. The results revealed that by using weed biological and ecological characteristics and its management based on density, diversity and distribution of species across the field, one may attains to more solid and safe results on the basis of weed control by using minimum, if any, amount of herbicide dose.

In order to study the effects of planting date and com density on com-redroot pigweed competition, a split plot design with three replications were conducted in 2001 in a field experiment at Ferdowsi University of Mashhad. Main plots were planting dates (21 May, 6 June) and pure stands of com at two densities (9.5 and 7.1 plant per m2) and pure and mixed stands of redroot pigweed at two densities of com were employed as subplots. Redroot pigweed density was 9.5 plant per m2 in both pure and mixed stands. Results showed that because of desirable environmental conditions at second planting date, redroot pigweed produced higher dry matter than the first. At the second planting date, redroot pigweed caused greater com yield loss at mixed stands. Because of shorter growth period and synchronization of anthesis and seed filling period with undesirable environment conditions at the second planting date, dry matter and seed yield of com was lower than the first. Total dry matter of redroot pigweed reduced as radiation decreased along with increasing com density.

In order to investigate the interference of common bean and redroot pigweed an experiment was conducted during 2003 in Lorestan Province. The experimental design was a randomized complete block in 3 replications. The experiment had two factors: crop density at 3 levels (20, 30, and 40 plants/m2), and redroot pigweed density at 5 levels (0, 2, 4, 6, and 12 plants/m2). Common bean biomass showed an asymptotic response to redroot pigweed interference. Redroot pigweed, and common bean maximum dry matter per plant were 27.9, and 13.4 g/plant respectively, that show growth potential of this weed in comparison to common bean. On the basis of logistic functions, redroot pigweed interference caused 35 % reduction of maximum common bean biomass per plant. Final height of redroot pigweed (77 cm) was more than twice of the final height of common bean. Coincident with redroot pigweed height raise, and overtopping (approximately 50 DAP) divergence between common bean height in presence and absence of redroot pigweed initiated. Approximately 25 % of redroot pigweed biomass was located in a height above common bean height. Crop plant density influenced economic thresholds of redroot pigweed competition. By increasing crop density from 20 to 30, and 40 plants/m2, economic injury threshold increased from 0.5 to 1 and 2.7 plants/m2, respectively. Increasing crop density from 20 to 30, and 40 plants/m2, reduced redroot pigweed seed production 23 % and 39 %, respectively. Crop plant density was the main factor in competitive ability, and economic threshold of common bean.

In order to study relative water content (RWC) and canopy temperature depression (CTD) under different water limited conditions in hexaploid triticale genotypes, the present investigation was carried out during growing seasons of 2001-2003, at Turogh field station, Khorasan Agric. Res. Center. This experiment was laid out in split plots design using RCBD. Main plots (L) were water limitations in different growth stages with 6 levels (L1, optimum conditions, L2, L3, L4 water limitation in vegetative pre anthesis, reproductive pre anthesis and post anthesis stages respectively, L5 and L6 received rainfall during cropping seasons with only one supplementary irrigation at anthesis and grain filling period respectively). Five hexaploid triticale genotypes (Jjuanillo 92 and four promising lines) were considered as sub plots. Results revealed that there was a reduction in RWC and CTD with development of phenological stages under optimum conditions, while no distinct trend was observed in water stress treatments. Imposing water stress during vegetative pre- anthesis phase. (L2) could significantly decline RWC and CTD only at flag leaf stage. However, reduction of RWC and CTD was not significant during anthesis and grain filling due to plant recovery during these stages. Minimum RWC and CTD were recorded during flag leaf and anthesis in L3 (water stress from double ridge to anthesis). Irrigation following water stress could not compensate RWC and CTD reduction even during grain filling period. Although these two indices were higher in L3 than post anthesis water stress (L4). Significantly positive correlations between yield, CTD and RWC were observed during all developmental stages. However, these correlations were higher in grain filling period. It was found that CTD is more reliable selection index for grain yield as compared to RWC. Result showed that there is a variation among genotypes concerning CTD and RWC in different development stages. Genotypes with higher yield under water stress expressed better CTD and RWC performance at different stages.

In order to evaluate the effects of limited irrigation on yield and yield components of three spring rapeseed cultivars (Brassica napus) in Tabriz an experimental design was conducted in Tabriz Agricultural Research Station in 2001. Experiment was a split plot on the basis of randomized complete block with four replications. In main plots, four irrigation treatments, including: 1.complete irrigation, 2. irrigation at sowing and stem elongation 3.irrigation at sowing and flowering, and 4.irrigation at sowing and seed filling were randomized. Three spring rapeseed cultivars, including early ripening Hyola 401, mid ripening option 501, and late ripening PF 7045/91 were allocated to subplots. Maximum yield was obtained from complete irrigation and late ripening cultivar PF7045/91 with mean seed yield of 2150 kg/ha. In this irrigation treatment yield of mid ripening cultivar Option 501 with 7 percent lower yield was not significantly different from PF7045/91, but early ripening cultivar Hyola 401 with approximately 25% lower yield showed significant difference with PF7045/91. In all three cultivars the lowest seed yield was obtained from limited irrigation in stem elongation stage. Mean seed yield in this treatment was 780 kg/ha and reduced by 60% compared to yield in complete irrigation. The influence of drought stress in this situation on late ripening cultivar was considerably more than two other cultivars. In all three cultivars with meeting the water requirements of plants through limited irrigation in floral stage, reduction in seed yield with respect to other stages was lower and approximately 27% less than complete irrigation. In ripening stage irrigation treatment effects of drought stress on seed yield was drastically more than limited irrigation in the time of flowering but was less than irrigation in stemming stage. Reduction of seed yield in this treatment compared to complete irrigation was 40% averaged over cultivars. The results showed that the best time for limited irrigation in rapeseed in Tabriz condition was at flowering combined with irrigation at sowing date.