فصلنامه علوم زراعی ایران
سال هشتم شماره 1 (پیاپی 29، بهار 1385)

A field study was conducted to evaluate the effects of shatter cane and soybean densities on soybean seed yield, and to quantify interspecific and intraspecific interference coefficients. The relationship between soybean seed yield per plant and shatter cane density at different densities of soybean and also with soybean densities at different densities of shatter cane is well described by the reciprocal model. Soybean seed yield per unit area decreased with increasing shatter cane densities. The highest yield loss (57%) was related to 50 and 12 plants/m2 of soybean and shatter cane densities, respectively. Optimum soybean densities on the basis of maximum soybean seed yield per unit area at 0, 4, 8, and 12 plants/m2 of shatter cane were achieved at 50, 34, 32, and 36plants/m2. The combined effects of soybean and shatter cane densities showed that shatter cane was a stronger competitor than soybean, as a shatter cane plant was equal to 2.5 soybean plants, based on soybean seed yield. In contrast, a soybean plant was equal to 0.18 shatter cane plant, on the basis of shatter cane biomass. It was, therefore, concluded that the superior competitor was mostly affected by intraspecific interference, but the weaker competitor was mostly affected by interspecific interference.

This study was conducted to evaluate grain yield and some of morphological traits in 20 promising wheat genotypes under non-stressed and post-anthesis drought stress conditions at Arak Agricultural Research Station during 2001/02 and 2002/03 cropping seasons. Experimental design was randomized complete block with three replications. Peduncle weight, grain number per spike, grain weight per spike, 1000 kernel weight, harvest index and grain yield were measured from plant samples taken at anthesis and maturity. Results of combined analysis of variance showed significant difference among genotypes for most of the measured traits. Under stress conditions grain weight per spike showed positive and highly significant correlation with harvest index (r=0.87**) and grain number per spike (r=0.76**). Days to heading showed positive and significant correlation with peduncle weight at anthesis. Harvest index also showed positive and highly significant correlation with grain number per spike (r=0.55**) and 1000 kernel weight (r=0.82**). Under non-stress conditions, grain weight per spike showed positive and highly significant correlation with harvest index (r=0.79**). Grain yield ha-1 also had positive and significant correlation with harvest index (r=0.67**), grain weight per spike (r=0.50*) and 1000 kernel weight (r=0.56*). Based on positive and highly significant correlation of grain yield with MP, GMP and STI under both non-stress and stressed conditions, these indices were identified as reliable criteria to select genotypes under terminal drought stress condition. Based on path analysis, direct effect of harvest index on grain yield was positive (0.76). The most indirect and positive effect of harvest index on grain yield was via grain number per spike and 1000 kernel weight. The most positive and negative direct effects on grain yield belonged to 1000 kernel weight (1.11) and grain weight per spike (-1.05), respectively.

To evaluate drought to lorance in promising dryland durum wheat genotypes, this study was carried out during two cropping seasons (2001-2003) in Maragheh Agricultural Research Station. Experimental materials included: seven promising durum wheat genotypes, one check (Zardak) and three bread wheat genotypes (one landrace, Azar-2 and Sardari). The experiment was conducted using RCBD with four replications under dryland and irrigated conditions. Quantitative criteria for stress resistance As: stress susceptibility index (SSI), tolerance index (TOL), mean productivity (MP), stress tolerance index (STI), and geometric mean productivity (GMP) were used for evaluation genotypes response to stresse. Results showed that in dryland condition effects of year and year genotype were highly significant (P0.01) on grain yield. In irrigated condition the main effects of year and genotypes were highly significant on grain yield. In comparison of the durum wheat genotypes with bread wheats the former had good tolerance under stresse condition and genotype no.4 (61-130/414-44//377-2/4/Df21-72//61-130/Uvy/3/128-13ya05509-1A-9A-2A-3A-OA-OAp) had the highest tolerance among the durum wheats.Among the criteria MP,GMP and STI had positively and highly significant correlation with grain yield under stress and non-stress conditions. Those criteriare recommended for screening of susceptible and resistant durum wheat genotypes for drought stren.

Flowering duration of canola is exposed to high temperature and heat stress in Khouzestan, Iran. The main objective was to examine the effects of sowing date and heat stress during flowering on yield and yield components of three spring canola cultivars. The experiment was conducted at Ramin Agricultural Research and Educational Center during 2003-4 and 2004-5 cropping seasens. Hyola-308, PF-7045/91 and Heros cultivars were planted as subplot in a split-plot experiment with three sowing dates 21 November, 10 and 30 December as main-plot with four replications. The results showed that biological and seed yields as well as yield components (except the number of seeds per silique) decreased significantly with delay in sowing date. Seed yield and yield components were significantly different among cultivars, however biological yield was not. Hyola-308 and Heros produced the highest (327.74 g.m-2) and the lowest (203.26 g.m-2) seed yields, respectively. The threshold temperature (Tt) during flowering was not significantly different among cultivars and their mean value was 28.3 °C. During flowering, the maximum daily temperatures greater than 28.3 °C were accumulated as heat stress units. The number of flowers and siliques per main raceme and the ratio of the number of developed siliques to the number of established flowers reduced as heat stress units increased, but the number of seeds per silique increased in Hyola-308 and decreased in two other cultivars. Based on the results of this study, middle and late maturing cultivars of canola are not suitable for Khouzestan climatic conditions, therefore, early maturing cultivars are recommended.

In order to determine the best planting dates and plant densities of maize for using of silage, two early and every early maturity maize cultivars (SC 108 and SC 301) were planted, in three planting dates (22 June, 1 Jul and 11 Jul) in two cropping seasons (2000-2001). Plant densities were 75000, 85000, 95000 and 105000 plants per hectar. A split plot design with threee replications was used. Sowing dates and plant densitties were assigned to main plots and sub plots, respecitively. Two experiments were carried out in two locations, Ghaemshahr (Gharakhyle) and Neka (Bayekola). Silage yield for each plot and each treatment was evaluated. Mean comparisons for silage yield performed using Duncan's Multiple Range Test. The best planting date and plant density were determined for two years. In Neka, for SC301 cultivar, the best plant density was 95000 plants per hectar with average silage yield of 44 t/ha, and for SC108 cultivar, highest silage yield was 41/7 t/ha with 105000 plants per hectar. In Ghaemshahr, for SC301 cultivar, the best plant density was 95000 plants per hectar with average silage yield of 42 t/ha, and for SC108 the highest silage yield was 36/9 t/ha and the best plant density was 105000 plants per hectar. In Neka, the best planting dates for SC108 were 22 Jun and 1 Jul. In Ghaemshahr this cultivar can be planted at 11 Jul. Result showed that SC301 had higher silage yield than SC108 sown following wheat harvest.

In order to investigate quantitative traits of mungbean [Vigna radiata (L.) Wilczk] genotypes, a field expriment was carried out in 1999 in the experimental Field station of the College of Agriculture, University of Shahid Chamran Ahvaz. This expriment was arranged as factorial-using randomized complete block design (RCBD) with four replications. Treatments included plant spacing at four levels of 15, 20, 25 and 30 cm on row (densities 133333, 100000, 80000 and 66666 plants/ha, respectivly) and three genotypes i.e. Partow, VC–1973A and 1-62-32. During the growing season, six samplings were harvested from plots and the total dry weight, leaf dry weight and leaf area were measured. At physiological maturity, grain yield was also measured. The results showed that among the three genotypes,1-62-32 was the best, and produced the highest grain yield (1723 Kg/ha). Growth parameters and indices including total dry weight (TDW), leaf dry weight (LDW), leaf area index (LAI), crop growth rate (CGR) and relative growth rate (RGR) were also measured. Among the three genotypes, VC-1973A and Partow had the lowest and highest specific leaf area (SLA) respectively. In this experiment Partow had the lowest grain yield (1439 Kg/ha). The highest (1713 kg/ha) and lowest (1379 kg/ha) grain yield obtained in plant spaces 20 and 30 cm on row, respectively. Increasing plant spacing on row increased seed yield per plant. Decreasing plant spacing on row increased TDW, LDW, LAI, CGR and SLA, however, RGR and NAR decreased. Considering the importance of SLA in increasing grain yield, it can be concluded that increasing grain yield in VC-19738 genotype was due to less SLA, therefore, it is recommended that SLA to be used as a selection criteria in Mungbean breeding programs.

To study drought tolerance in inbred lines is an important task in development of maize hybrids with acceptable yield in moisture limited conditions. Twenty maize inbred lines were evaluated in three moisture conditions, normal irrigation, moisture stress in vegetative and reproductive stages, in three separate experiments, using randomized compelet block design with three replications, in experimental field of Seed and Plant Improvement Institute, Karaj, Iran in 2005 cropping season. Results using TOL and SSI indexes revealed that K3651/1 and K3615/1, as tolerant inbred lines under stress conditions in reprodutive and vegetative stages respectively. These two indexes identify genotypes with low yield under normal and high yield under stress conditions. The higher value of MP, STI, GMP and Harm indexes indicate the tolerance of genotypes under consideration. K3615/2 (with 4.770, 2.700 and 2.430 t/ha) and k19/1 (with 4.200, 2.830 and 2.510 t/ha) under normal, stress conditions in vegetative and reproductive revealed as the high yielding lines underthree moisture conditions.