مجله تولید گیاهان زراعی
سال دوم شماره 3 (پاییز 1388)

Understanding the variation of kernel number per unit area (KNO) is an important factor in respect yield and in identifying opportunities to increase potential yield. Some crop models are for dependence on kernel number prediction to yield simulation. In order to quantify the relationship between kernel number per unit area and influencing parameters (Environment and non-environment-based factors), compound analysis with randomized complete block design was conducted including four replications. This experiment was done at the Gorgan University of Agricultural Sciences Research Farm in 2005. The treatments were five different sowing dates (14 December, 20 Jan, 20 Feb, 20 March, 16 Apr) and four wheat variations (Kohdasht, Shirudi, Tajan, Zagros). Considering results of correlation coefficients, kernel number per unit area appeared to have the best relation with mean temperature, but Non-linear models fitting indicated that the highest R2 and the lowest CV belonged to stem dry matter at anthesis. Fitted model showed that 95% of kernel numbers are formed when stem dry matter is around 747 g.

Concerning limitation of water resources, determination of the least water that can lead to the maximum yield is of great importance in crop production. In order to evaluate effects of deficit irrigation on grain yield and water use efficiency of some wheat)Triticum aestivum) cultivars under different climatic conditions, two similar field experiments were conducted in 2004 in Agricultural Research Stations of Azad University of Karaj and Torbat-Jam (central and eastern part of Iran, respectively). The experiments were conducted as a randomized complete block design in a factorial arrangement with four replications. First factor was consisted of 9 different irrigation regimes, including a control treatment (irrigation at 40% soil moisture depletion), and irrigating when 60 and/or 80 percent of soil moisture was depleted from stem elongation to ripening, from the start of flowering to ripening, only at flowering stage, and irrigation termination at flowering and grain filling stages. The second factor was consisted of three wheat cultivars, including Chamran, Marvdasht and Gaspard. Results showed that yield, harvest index and water use efficiency were affected by water stress, as plants in control treatment produced the highest grain and biological yields, harvest index and water use efficiency. Water use efficiency varied from 0.17 to 1.34 kg m-3 between irrigation regimes. Deficit irrigation and drought stress at the end of season influenced yield and WUE extremely, whereas limited irrigation at early growth stages had no significant effects. Responses of wheat cultivars to irrigation regimes varied between two locations and warmer and drier conditions in Torbat-Jam lead to more water consumption and lower water use efficiency. Among measured characteristics, seed yield had the most direct effect on WUE and following that, total water used was accounted reasonably for the rest of variation in WUE. Thus it seems that wheat irrigation management, especially during late of growth season, is so important, and should be involved climatic conditions of each location as an effective variable.

The inheritance of cold resistance was evaluated at the germination stage in crosses between seven rice genotypes as half diallel. Analysis of variance indicated that there were highly significant differences among the genotypes, general combining ability (GCA) and specific combining ability (SCA) for percentage of reduction in radicle length (RL), percentage of reduction in plumule length (PL) and percentage of reduction in germination (GP). Significance of GCA and SCA revealed that additive and non-additive gene effects were controlled the inheritance of studied traits, but according to the higher magnitude of the dominance variance than additive variance and low value of genetic ratio showed that non-additive gene action was predominant than additive. Broad-sense heritability were 86, 68 and 81% for RL, PL and GP respectively. The assessments of GCA effects revealed that Deilamani was an ideal general combiner characters and superior variety for all Hassani was also a good general combiner for PL and GP. The degree of dominance were 1.93, 1.26 and 0.99 for RL, PL and GP respectively and indicated over-dominance of gene effects for RL and PL and dominance effects for GP.The estimates of SCA effects of top ranking crosses indicated that Neda×Hassani could be regarded as the most desirable cross combination for all of three traits. In this cross SCA effect and estimated heterosis were significant and negative. Consequently crosses that Hassani and Deilamani was one of the parents, indicated desirable SCA effects for all of the traits, and could be used for breeding programes.

In order to determination of partitioning N fertilizer by using of Leaf Color Chart (LCC) and Chlorophyll meter (SPAD) in rice an experiment was conducted as split plot under randomized complete block design with three replications during 2006 and 2007 at Rice Research Institute of Iran. Main plots were contained cultivars in three levels (GRH1, Khazar and Hashemi) and sub plots were contained six time of application N fertilizer as LCC<3 (application of N fertilizer after observation of 3 degree in Leaf Color Chart), LCC<4 (application of N fertilizer after observation of 4 degree in Leaf Color Chart), SPAD<35 (application of N fertilizer after time that degree in SPAD was under 35), SPAD<38 (application of N fertilizer after time that degree in SPAD was between 38 and 35), common method (application of 150kg N fertilizer in tillering, panicle initiation and flowering) and no fertilizer. Significant deference was detected between cultivars for all of the traits in 1% probability level. Also, significant deference was identified between tools for all of the traits (unfilled grains and thousand grain weight) in 1% probability level. Significant deference was showed between SPAD<38 and LCC4 with other methods of partitioning, whether non significant deference was detected between common method with LCC<3 and SPAD<35. According to these result, level of optimum SPAD was identified 35 for Hashemi. Also, levels of optimum LCC and SPAD were identified 4 and 38 for GRH1 and Khazar, respectively. Result of this study were showed when LCC and SPAD values were under than optimum level, N fertilizer should be used as 35 (for Hashemi) and 40 (for GRH1 and Khazar) kg N fertilizer per hectare.

The aim of this research was to compare more and less competitiveness of rice cultivars against barnyardgrass for light extinction coefficient and canopy structur. A filed experiment was conducted in 2007 growing season in Tonekabon’s rice research station in Mazandaran province. The experiment layout was a factorial design with four randomized complete blocks. Seven rice cultivars (Khazar, Sepidrood, Nemat, Dorfak, Fajr, Shiroodi, and Dailamani) and three lines (Line 830, Line 841 and Line 843) were transplanted with and without competition with barnyardgrass. Each cultivar or line was planted at its own optimum density, while density of barnyardgrass was 20 plants per square meter. Results showed that Khazar cultivar compare to Line 843, had higher light extinction coefficient. Under both weedy and weed free conditions, in Line 843, dry matter accumulation and leaf area in each layers of canopy were more than those for Khazar variety. Furthermore, in Line 843, dry matter accumulation and leaf area in top layer of canopy were more under weedy condition. On the other hand, the dry matter accumulation and leaf area of barnyardgrass in interference with Line 843 was less than that in interference with khazar cultivar.

The process of adaptation to cold is an important mechanism in wheat cultivars to tolerate cold stress. This work was aimed to calrify the relationship between vernalization requirement with cold tolerance by assessing physiological changes in cold susceptible spring and tolerant winter wheat (Triticum aestivum, cvs. Kohdasht and Cheyyene, respectively) in environmentally controlled conditions, using factiral experiment on the basis of completely randomised design (CRD). By using final leaf number (FLN) method, the vernalization saturation and by using LT50, the level of cold tolerance were determined in both wheat cultivars. FLN results verified no vernalization requirement in Kohdasht and vernalization saturation in Cheyyene at 42nd-d of exposure to 4°C. The results of LT50 proved the maximum cold tolerance on either 42nd-d in Cheyyene (-17°C), or -2°C in Kohdasht (fixed at cold treatment period). The relationship of cholorophyll fluorescence, chlorophyll content (SPAD), proline and total carbohydrates with cold tolerance were studied. The results indicated that cholorophyll fluorescence was less influenced in Cheyyene than in Kohdasht in response to cold stress. Vernalization cold caused significant 30% decline in chlorophyll content in Kohdasht and 36% increase in Cheyyene cultivar on vernalization saturation time (day 42). At this time, 3- and 2-fold cold-induced accumulations of proline and total carbohydrates, respectively were detected in Cheyyene compared to Kohdasht cultivar. In conclusion, such physiological results verified the advantageous response to cold of vernalization required-cultivar in comparison with non-vernalization required-cultivar.

In order to investigation of morphological traits, yield and its components in three cultivars of grain sorghum (Kimia, Sepideh, Payam) and two promising lines (M5, M2) under four density (240000, 205000, 170000 and 135000 plant/m2), experiment was conducted as factorial design based on randomized complete block design with three replications in Birjand agricultural research station, during 2002 and 2003 grown season. Grain yield, yield components and some of morphological traits were measured. Combined analysis results from two years (2002 and 2003) showed that cultivars and lines were significantly different at 1% level for all traits except grain yield. Different plant densities were significantly different for tiller number, biological yield and grain yield at 1% level and stem diameter at 5% levels. Interaction between cultivar and density was significantly different for tiller number and harvest index at 1% level. According to the results, we can recommend the density of 240000 plant/ha and M5 promising line in Birjand.

In order to study the effects of different nutrition systems (organic, chemical and integrated) and biofertilizer (PGPR) on phenology period, grain yield and its component in sunflower (Helianthus annuus L.) an experiment was conducted using Alestar cultivar at the research farm of college of agriculture, Tarbiat Modares University in 2007. Five levels of nutrition systems including F1 (100% organic), F2 (75% organic + 25% chemical), F3 (50% organic + 50% chemical), F4 (25% organic + 75% chemicaL), F5 (100% chemical) in main plot and two levels of biofertilizer I1 (inoculation) and I0 (control) as subplot were used in a split plot arranged in a randomized complete block design with three replications. Results showed that chemical treatment (100% N) decreased phenology period GDDs but treatment (100% FYM) increased it. Different nutrition systems and biofertilizer significantly affected yield, plant height, biological yield, harvest index (HI), seed oil content, The results revealed that the maximum grain yield, plant height, biological yield, harvest index (HI) was recorded in integrated system F3 (50% organic + 50% chemical). The grain yield in integrated system was more than organic and chemical systems (F3›F4›F2›F5›F1). Bacterial inoculants with PGPR (I1) showed an increase in grain yield and yield components when compared campared to the control.

To evaluate the competition between wheat and wild mustard (Sinapis arvensis) in nitrogen and herbicide levels, an experiment was conducted in Ramin Agriculture and Natural Resources University, at 2007-8. A split-plots design in RCBD (Randomized Complete Blocks Design) with three replications was used for this experiment. The nitrogen levels (0, 60, 120 and 180kg/ha) arranged in main plots. Each main plot was be splitted to five sub-plots, and herbicide levels (0, 15, 20 and 25g three benoron methyl/ha) with hand-weeding as a control treatments were arranged in sub-plots. The results showed that the interaction effect between nitrogen and herbicide levels on grain yield (GY) of wheat and dry matter (DM) production of wild mustard was significant. With increase of nitrogen, while herbicide levels were low or no control was be done, GY of wheat and DM of wild mustard decreased and increased, respectively. It can be said that in high levels of nitrogen, more herbicide will be required for weed management. In low levels of nitrogen, difference between herbicide levels was little and DM of wild mustard decreased significantly. Generally, increase of nitrogen caused to decrease of wheat competition ability against wild mustard and also caused to requirement more herbicide. Highest DM of mustard was produced with 180kg N/ha without weed control. In the other hand, highest GY of wheat was gained by 180kg N/ha and 20g three benoron methyl/ha.

In order to evaluate plant density and different nitrogen levels on protein percent, yield and nitrate accumulation in potato tuber cv. Agria, a factorial experiment based on randomized complete block design with three replications was conducted in Ardabil in 2006. Factors included nitrogen levels: 0, 80, 160 and 200 kg ha-1 net nitrogen and plant densities: 5.5, 7.5 and 11 plant m-2. Results showed that plant density of 11 plant m-2 caused the higher rates of tuber number, tuber dry weight, tuber yield and protein per unit area. The lowest mean tuber weight and protein percent was derived in this density, as well. With increasing nitrogen level up to 80 kg ha-1, number, yield, dry weight and protein content of tuber was increased. In plant density×nitrogen level interaction treatment, the most nitrate concentration in tuber dry weight was achieved using 200 kg ha-1 net nitrogen and density of 5.5 plant m-2. So, based on the results, application of 80 kg ha-1 net nitrogen and density of 11 plant m-2 to get the highest yield and protein and the lowest nitrate concentration in tuber under the Ardabil conditions is recommended.