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.

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.  

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.

The present research has been conducted to parameterize and evaluate the APSIM-WHEAT model for WINTER WHEAT and to use the model for evaluation of climate change effects on grain yield. The model is used to simulate leaf area index, dry matter, and grain yield of Roshan cultivar WINTER WHEAT in Karaj and Khomein regions between 2014 and 2015, under four irrigation regimes and three levels of nitrogen fertilizers. The experiments have been conducted in both regions as split-plot in a randomized complete block design. Irrigation is considered as main plot and nitrogen as a sub-plot. Model parameterization is based on observational data from full irrigation and 200 kg/ha nitrogen treatment in both regions. Results from the model evaluation show that the simulated values closely predict the observed values so that the RMSE in both regions is less than 670 and 450 kg/ha for biomass and yield, respectively, being below 0. 56 for leaf area index as well. Normalized RMSE in all treatments has been below 17. 8%, with Wilmot's index being above 0. 82. The evaluation of model shows high performance and its possible use in other studies. Results from climate change analysis show that increasing the temperature from 0 to 5 ° C leads to a maximum reduction of 75% in grain yield and an increase in carbon dioxide concentration, resulting in a maximum increase of 24% and, if the temperature increase exceeds three degrees Celsius, the grain yield will decrease in all possible concentrations of carbon dioxide.

To evaluate the effect of false seedbed preparation on rye (Secale cereale L. ) control, an experiment was conducted during 2013 in Shahrekord. Experimental factors were arranged in split plot factorial design with three replications. The main plots included seed bed preparation at three levels: 1. conventional dry cultivation of WHEAT, 2. seedbed preparation, irrigation, weed control (including rye) with paraquqt (20% SL) at 2 L ha-1 after one month, WHEAT cultivation, 3. seedbed preparation, irrigation, mechanical weed control (using harrow), WHEAT cultivation. Subplots 1. included cultivars at three levels (Alvand, Pishgam and Back Cross Roshan) and 2. planting densities at three levels (200, 250 and 300 kg ha-1). According to the mean comparison, density and biomass of rye in the treatment of irrigation + application of herbicide decreased relative to dry cultivation by 67. 7 and 74. 9 percent, respectively, Pishgam cultivar decreased rye density and biomass by 36. 9 and 18. 7 percent, respectively. The seeding rate of 200 kg ha-1 of WHEAT reduced density and biomass of rye by 24. 3% and 22. 4%, respectively. The highest grain and biological yield of WHEAT was observed in irrigation and application of paraquat with 4206 and 8872. 3 kg ha-1, respectively. Based on the results of this research, for weed control, especially rye, yield and yield components of WINTER WHEAT, the best method of seedbed preparation, is false seedbed preparation using chemical control of weeds. The best WHEAT cultivar, was Pishgam and best WHEAT seeding rate, was 200 kg ha-1.