To achieve a higher grain yield in WHEAT the matching of vegetative and reproductive stages of growth with the optimum environmental conditions, through a selection of appropriate planting date and rate, is crucial. The appropriate planting date and seeding rate for WINTER WHEAT CV. SHIRAZ under SHIRAZ environmental conditions has not yet been studied in detail. The present experiment was conducted during 2001/2002 and 2002/2003 growing seasons at the Experimental Farm of SHIRAZ University, College of Agriculture located at Badjgah, using RCBD with a split plot layout of four replicates in either year. Main plots consisted of three planting dates (November 6th, December 6th and January 6th) while four planting densities (150, 250,350 and 450 plants/m2) were chosen and layed out as subplots. The results indicated that planting date significantly affected grain yield, number of grains per spike, number of spikes per m2 and 1000 grain weight, so that the highest grain yield was achieved for the second planting date (i.e.Dec.6th) and a delay in sowing date was accompanied by a significant decrease in grain yield. In the first sowing date, due apparently to coincidence of flowering with a period of low temperature, florets were not fertilized appropriately and hence the number of grain per spike was decreased significantly. In addition, the number of spikes per m2, grains per spike and 1000 grain weight were significantly affected by planting densities, so that the highest number of spikes per m2 was obtained for the highest planting density (i.e. 450 plants/m2) however, the highest number of grain sper spike and mean grain weight were obtained for the lowest planting density (i.e. 150 plants/m2). With increasing plant density, the number of spikes per m2 increased for all planting dates. Altogether, the results revealed that December 6th and 350 plants per m2 were the most appropriate planting date and rate for WHEAT (CV. SHIRAZ) under environmental conditions in Bajgah or under similar climatic conditions.

Plant growth regulators (PGRs) are widely used for lodging control in WINTER WHEAT (Triticum aestivum L.) grown at high N rates. Although the introduction of semi-dwarf WHEAT cultivars had largely solved the problem of lodging, evidence was already accumulating that the timely application of a growth retardant such as chlormequat (CCC) or ethephon could increase the grain yield of WHEAT, by the alteration of dry matter partitioning independently of any control of lodging. A field experiment was conducted the during 2004-5 growing season at the experimental farm of the College of Agriculture, SHIRAZ University (SHIRAZ, Iran,) located at Badjgah. The design of the experiment was a randomized complete block with treatments arranged as split plot with four replicates. Nitrogen levels (0, 100 and 200 kg ha-1) were the main plots. The N was applied as Urea (46% N), half at the time of stem elongation and the other half at onset of flowering. The PGR treatments included CCC at 2.20 kg ha-1 applied at Zadoks growth stage (ZGS) 25, ethephon at 0.28 kg ha-1 at Zadoks growth stage (ZGS) 39, and controls (without any PGR) were assigned to sub-plots. The results showed that both PGR treatments reduced the plant height and this reduction played an important role in the increase of the grain yield in WHEAT, via the alteration of dry matter partitioning into the spikes. However, CCC at 2.20 kg ha-1 applied at ZGS 25 increased the grain yield (8.9 t/ha) significantly, compared to the ethephon (8.2 t ha-1) and control (7.2 t ha-1) treatments; the highest grain (8.9 t ha-1) yield was obtained at 200 kg ha-1 N and 2.20 kg ha-1 CCC application. The beneficial interactive effects of PGRs and nitrogen rates on WINTER WHEAT yield are worthy of further exploration.

Development of WHEAT (Triticum spp.) is primary driven by temperature, but is also affected by other factors such as vernalization and photoperiod. Crop growth and development are often described in terms of calendar days. However, determining the development in terms of thermal time or physiological time is more accurate because it is an accumulation of the caloric energy needed for the occurrence of phenological stages. The objectives of this study were: (i) to determine the base temperature for key phenological stages of different WINTER WHEAT cultivars and (ii) to develop a phenological model using the base temperature for predicting the duration in terms of thermal time for different phenological stages. Eight WHEAT cultivars were selected according to their vernalization period to determine the base temperature for three critical developmental phases, i.e., planting to heading, heading to harvest and planting to harvest. For each cultivar, the base temperature for each critical period was estimated as well as the duration of the three key phenological stages in terms of thermal time for three locations in Georgia from 1999 to 2010. The base temperatures and the growing degrees varied widely depending both on the developmental stage and the cultivar. The estimated base temperatures for the eight WHEAT cultivars ranged from 3.1 to 8.1oC, 10.6 to 18.4oC and 1.6 to 8.4oC, for planting to heading, heading to harvest maturity and planting to harvest maturity. Also, the duration in Growing Degree Days (GDD) was determined for each season and cultivar. When 0oC was used as the base temperature, the GDD between cultivars varied from 1675-1844, 1017-1239 and 2827-2936oC from planting to heading, heading to harvest maturity and planting to harvest maturity, respectively. The results from this study provided specific base temperatures for each developmental stage for each individual cultivar and, therefore, provided a more accurate estimation of GDD. The variation in base temperature and GDD accumulation is probably a selective advantage for WINTER WHEAT. Clearly more work is required to estimate the base temperatures and duration for others phenological stages and further evaluation is required for additional cultivars and a wider range of environments.

IntroductionThe yield of WHEAT (Triticum aestivum L.), is greatly reduced under environmental stress and decreased temperatures. Therefore, adaptation mechanisms and cold resistance are crucial in this plant. Vernalization is known as one of the essential mechanisms for grain adaptation to environmental conditions, whereby the plant can accelerate the flowering process or flower after a long cold period. Vernalization also plays a significant role in the acquisition of cold resistance in WHEAT plants. When exposed to low temperatures, certain genes related to vernalization are activated, leading to changes in the plant's physiology and allowing it to a better cold stress tolerance. This process involves complex regulatory mechanisms depending on the cultivar and environmental conditions. Understanding the molecular basis of vernalization and the genes involved in cold resistance could assist in developing new strategies to improve WHEAT productivity in adverse environments.Materials and methodsIn this research, we investigated the expression of three genes, NAC, ERF, and TCP, related to vernalization in two WHEAT cultivars named Baz and NorthStar, which known as spring and WINTER cultivars, respectively. The plant samples were preserved in growth racks and applied for vernalization treatment after the tillering stage. RNA extraction was performed at this stage. Real-Time PCR technique was then utilized to analyze the gene expression. To better understanding the function of these genes in response to cold stress, the promoter of the three studied genes was analyzed by screening 500 nucleotides upstream of the WHEAT TSS. The vernalization treatment was applied at two levels of 14 and 21 days and compared to the control plants under 4°C.Results and discussionThe results showed that the expression of all three genes (TCP, NAC, and ERF) decreased under the vernalization treatment. However, the expression of the TCP and NAC genes increased after 14 and 21 days of treatment in the NorthStar and Baz varieties, respectively. In general, the decreased level of expression was shown by increasing in the number of vernalization days. Notably, the expression of the ERF gene reduced in both tested varieties with the increased number of vernalization days. This trend was also observed in the expression of the NAC gene. However, the vice versa was observed for NAC gene in the Baz variety by an increased expression. In the Baz variety, the expression rate of the TCP gene decreased with an increase in the number of vernalization days, whereas in the NorthStar variety, the gene expression increased and then decreased after 14 and 21 days of treatment. Based on the abundance and diversity of the identified elements resulting from the analysis of the promoters of the studied genes, 28 types of regulatory elements were identified, many of which are binding sites for transcription factors responding to biotic and abiotic stresses Top of Form.ConclusionDespite the similarity of the pattern of expression changes of all three genes in the two investigated cultivars, the intensity of the changes in the two cultivars was not same, which could be due to different reactions to cold stress. The results show the complexity of gene expression regulation in WHEAT vernalization. Additionally, the multiplicity of stress-responsive transcription factor binding sites in the promoter region of these genes could be a justification for the complexity of regulating their expression during vernalization and response to cold stress.

In order to modeling of growth stages and yield of WHEAT according to Hamedan province meteorological data (minimum and maximum temperature, radiation and rainfall) By using the sub models of phenology, production and distribution of dry matter and leaf area changes in maize studies was conducted at the Faculty of Agriculture, University of Vali-e-Asr Rafsanjan in spring 2015. The parameters of sub model were estimated according to data from previous researches in Iran and other countries. Daily changes of phenology, harvest Index total dry matter and leaf area was calculated using the model and the yield at the end of season was predicted. One of the criteria to evaluation of a model is Comparison between coefficients of linear regression of observed and predicted yield (b=0. 90± 0. 67 and a=0. 73± 0. 10) and coefficients of line 1: 1 (1, 0). Accuracy of the model related to coefficient of variations of predicted and observed seed yield (CV. 7. 28) was very high so that in field experiments coefficient of variations limit is 20 to 25. R2 quantity of seed yield was 0. 81; showing that the probability for coordination of predicted and observed data is 81 percent. The Root mean square error is the other statistics which is used to evaluation of model accuracy. The Root mean square error of seed yield was 0. 43, which is evidence of accuracy of model for yield prediction. domain variation for observed and predicted data were 4. 08-8. 01 tones and 4. 08-7. 59 tons per hectare respectively and the means were 6. 09 and 5. 53 tones per hectare respectively.

The study area is about 36,000 hectares and is located in Mianab area (Shooshtar district) in Khuzestan Province, Iran. It is between 31° 35' to 32° north latitude and 48° 50' to 49° east longitude. Based on nearest synoptic stations to the study area, the climate of the area is semiarid. The maximum daily air temperature is 46.7 °C in June and the minimum daily air temperature is 7.1 °C in December. The annual rainfall is about 325 mm. The growing period in area starts from December 4, and ends in March 10, which is about 96 days. The aim of this research was comparison of land suitability classification with different methods for finding the best methods, which suit the area. In this respect four methods were used simple limitation method, limitation regarding number and intensity of limitation, parametric method (Storie method) and parametric method (square root method). For this purpose 75 soil profiles were studied and classified up to family level, with using Keys to Soil Taxonomy (USDA, 1998). There were 20 families and 40 phases of the families. The main subgroups were Typic Ustitluvents, Typic Haplustepts, Calcic Haplusteps, Haplocalcic Haplustepts, Fluventic Haplustepts, Calcic Aquisalids and Typic Haplosalids. The results of land suitability classification show that the main soil-related limitations are salinity, alkalinity, drainage, calcium carbonate, and climate-related limitations are mean daily temperature and amount of rainfall during late season stage of growing cycle. The results of four different land suitability methods show that simple limitation method, limitation regarding number and intensity of limitation, and parametric method (square root method) are closely related, but the application of Storie method leads to a land suitability class which is one level lower, compare to other methods. Field observation demonstrated that Storie method failed giving satisfactory results in the study area. The results obtained, recommend that simple limitation method or limitation regarding number and intensity of limitation are more appropriate for qualitative land suitability classification and parametric is more accurate for quantitative land suitability classification purposes.