Background and Objectives: Nowadays, climatologists and researchers are interested in the long-term forecast of climatic variables to be informed about the extent of their variations and to take measures to mitigate the adverse effects of climate change. Accordingly, general circulation models (GCMs) of atmosphere have been developed to predict climatic parameters. LARS-WG is a model to downscale the output of GCMs. It was used in the present research to generate data of daily precipitation, radiation, and minimum and maximum temperature across the cotton cultivation climatic zones (Meteorological stations) in Iran. The objective of this study is to estimate climatic factors (rainfall, radiation and minimum and maximum temperature) in the future period in major climatic cotton cultivation areas in Iran, which may be used for optimized water resource preservation and management in these regions. Also, the 5th IPCC report was used in this study, in contrast with the majority of investigations that use the 4th report. Materials and Methods: In this research, the important areas under cotton cultivation in Iran are the target area. The data of 23 synoptic stations were used in these areas. The required meteorological data recorded in the stations were daily rainfall, minimum temperature, maximum temperature and sunshine. The present study assessed the performance of five different GCM models in simulating the data of precipitation, radiation, minimum temperature, and maximum temperature in nine synoptic stations (SABZEVAR, GHOOCHAN, GHOM, HASHMABAD, LAR, BILESOWAR, EDAREGORGAN, HASANABADEDARAB, and MASHHAD) from 2011 to 2016, firstly. Finally, two GCMs (MIROC5 and GFDL-CM3) were selected for the research purpose based on the results of t-test, F-test, and the Kolmogorov-Smirnov non-parametric test. Then, the parameters were predicted by the selected GCM models for 20 years (2041-2060) under the emission scenarios of RCP4.5 and RCP8.5. Results: According to employing the scenarios of RCP4.5 and RCP8.5, the predicted solar radiation does not show a significant change in the future period versus the base period of 1981-2010 in all studied regions based on both GCM models. The highest change (0.249 MJ / m2 / day) is based on the MIROC5 model and the RCP8.5 scenario in climate zone 6102 (HASHMABAD station). The predictions revealed that the parameters of maximum and minimum temperature would be ascending for all the climatic regions over the future period. The highest variations in the average long-term annual minimum and maximum temperatures versus the base period would be 2.67 and 2.75°C happening in Climatic Region 6002 Includes stations (HASANABADEDARAB, KHAF, HAJI ABAD and GONBAD) over the 2041-2060 period under Scenario RCP8.5. For both scenarios RCP4.5 and RCP8.5, the highest temperature increase was observed in the climatic zones where located in south of Alborz and the east of Zagros mountain chains as well as the Central Iranian Dry Plateau and the lowest increasing was in the climatic regions located around the Caspian Sea, the Persian Gulf and the south of Iran. For the total annual precipitation over the future period (2041-2060), the highest amplification was predicted by MIROC5 to be 98.5 mm under Scenario RCP4.5 in Climatic Region 6202 (EDAREGORGAN station), and the greatest loss of precipitation was predicted by the same model to be -29.8 mm in Scenario RCP8.5 in Climatic Region 6102. Conclusion: Given the prediction of rising average annual minimum and maximum temperature and the decline of precipitation over the future period (2041-2060) in the climatic regions leading to the arid plain of central and southern Iran, it can be concluded that the variations of meteorological parameters induced by climate change will be significant in the cotton-growing climatic regions of Iran over the future decades.
Background and objectives: Sunflower (Helianthus annuus L.) is one of the most important oil plants, which is cultivated due to the high seed oil and adaptation to different climatic and soil conditions in a wide range of arid and semi-arid regions of the country. Due to the possibility of drought stress in these areas, it is essential to take action to cope with these stresses. One of the methods to reduce drought stress is the use of plant growth regulators. Considering that brassinolide is the plant growth regulating steroidal substance that can affect the increase of plant resistance against different stresses. Therefore, the aim of this study was to investigate the effects of brassinolide foliar application on some physiological and agronomic characteristics of sunflower in one of the semiarid areas of the country. Materials and methods: The experiment was conducted in the Noorabad area of Fars province using split-plot in a randomized complete blocks design with three replications and nine treatments in 2018. The main factor of the experiment included irrigation at three levels which consisted of without stress (100 percent of full irrigation), moderate stress (75 percent of full irrigation), and severe stress (50 percent of full irrigation) according to evaporation from class A pan, and sub-factor including the application of brassinolide hormone at three levels (0, 0.1 and 0.5 mg/L). Results: The results showed that yield, number of seeds per head and weight of 1000 sunflower seeds were affected by experimental treatments, using 0.5 mg/L brassinolide foliar application under severe drought stress conditions can significantly increase chlorophyll content and number of leaves per plant, therefore, the yield, number of seeds per head, 1000-seed weight and oil yield increased compared to control treatment. The highest grain yield (313.3 g/m2) was obtained in complete irrigation treatment and 0.5 mg/L brassinolide foliar application, so that 55% of the grain yield was higher than the control treatment. Also, the percentage and yield of oil were reduced under drought stress but the amount of these two traits was increased with brassinolide hormone application. The highest leaf proline content observed in 0.5 mg/L brassinolide foliar application and the lowest of this trait was obtained in the control treatment. Conclusion: The results of this experiment showed that the use of brassinolide foliar application under severe drought stress conditions can increase drought tolerance by 63%. Therefore, under severe stress conditions, the use of brassinolide foliar application can be a solution to increase the production of sunflower .
Background and objectives: Barley (Hordeum vulgare L.) is one of the most important plants in the cereal family after wheat, rice and corn. Barley is the second most important crop in Iran after wheat in terms of agricultural value and nutrition. The purpose of this study was to evaluate and select superior lines with high yield, early maturity and dormancy resistance in warm regions of the south and north of the country using the selection index of ideal genotype (SIIG). Materials and methods: In order to selection of pure barley lines with high yield and desirable agronomic characteristics in the warm regions of the south and north of the country, 108 pure lines in the non-repeating Augment design with four controls (Norooz /Sahra, Auxin, Nobahar and WB-96-19) in three blocks, in the Centers for Agricultural Research and Education and Natural Resources Fars (Darab), Ahvaz, Sistan (Zabol) and Golestan (Gonbad) were evaluated during 2019-20 cropping year. Results: The results of restricted maximum likelihood (REML) analysis showed that the heritability of grain yield in Gonbad, Ahvaz, Darab and Zabol were 0.993, 0.258, 0.498 and 0.063, respectively. The results of correlation analysis showed that there is a positive and significant correlation between SIIG index and plant height, 1000-kernal weight and grain yield in all regions. SIIG index showed that 21, 28, 16 and 5 lines in Darab, Ahvaz, Zabol and Gonbad, respectively, with high SIIG index value (0.6-0.9) were the best lines. Based on the results of the average SIIG index of lines 68, 102, 44, 66, 13, 47, 16, 34, 46, 99, 25, 65 and 35, respectively, with SIIG value higher than 0.500 were the best lines in most regions, so they are recommended for cultivation in later years and for advanced testing and compatibility. In order to evaluate the efficiency of SIIG index in selecting the best lines in terms of grain yield, 1000 kernel weight, plant height and early maturity, the studied lines were grouped based on SIIG index in different regions. The studied lines were classified into 6, 7, 8 and 7 groups in Darab, Ahvaz, Gonbad and Zabol, respectively. Conclusion: Based on the results of the average SIIG index in all regions, 16 lines with the highest average value of the SIIG index were top lines in most regions. Selected lines in each region can be recommended for experiments in that region, and lines with the highest SIIG values in most regions for additional testing in all introduced regions in later years.
Background and objectives: Undoubtedly, one of the biggest human challenges in the present age is food security, and salinity stress is one of the main obstacles to achieve this goal. In this regard, this experiment was conducted with the aim of selecting tolerance barley cultivar(s) to salinity stress and identifying tolerance mechanisms in new and old barley cultivars. Materials and Methods: This experiment was carried out during the two years of 2016-17 in the Milshbar Ardakan region located in Yazd province. Experimental treatments included 9 six-rowed barley cultivars including Nik, Mehr, Khatam, Reyhan, Goharan, Nosrat, Morocco, Afzal and Fajr 30 cultivars in three levels of irrigation water salinity including 4, 10 and 14 dS/m were evaluated as a split plot experimental design so that water salinity as the main plots and cultivars as a sub-plots were randomly placed. The studied traits included yield and yield components. At the maturity stage, several plants were selected from each experimental plot and sodium and potassium were measured. Results: The results showed that salinity and cultivar treatment had a significant effect on the yield and yield components including number of seeds per spike, number of spikes per square meter and 1000-kernel weight. Salinity stress reduced grain yield components and among the studied cultivars, Nik, Mehr, Khatam and Reyhan cultivars had higher yield and yield components. Among the salinity treatments, the highest grain yield was obtained at 4 dS/m with 5770.64 kg/ha. With increasing salinity to 10 and 14 dS/m, grain yield decreased by 18.04 and 27.55%, respectively, and reached to 4729.29 and 41.8080 kg/ha. Among the studied cultivars, the highest grain yield was obtained in Nik with 5317.7 kg/ha and Mehr, Khatam and Reyhan were not significantly different with this cultivar. In salinity of 10 dS/m, the lowest grain yield variation were obtained in Goharan and Mehr cultivars and in salinity of 14 dS/m it was in Mehr and Afzal cultivars. The highest STI index in salinity of 10 compared to 4 dS/m was calculated in Nik and Mehr cultivars with 0.922 and 0.921, respectively. The highest value of this index in salinity 14 compared to 4 dS/m was also obtained in Nik and Khatam cultivars with 0.882 and 0.858, respectively. Conclusion: Considering the amount of sodium and potassium absorbed by the plant and the K/Na ratio, it seems that tolerant cultivars cope with salinity stress by the mechanism of potassium uptake and excretion of sodium and regulation of cell osmotic potential. In general, among the studied cultivars, Nik, Mehr and Khatam cultivars had higher stress tolerance indices of STI, MP, Tol and these cultivars can be used for cultivation in saline lands of the region as well as for hybridization and breeding programs.
Background and objectives: Biotic stresses affect the yield and yield components of cotton. Alternaria leaf spot (caused by Alternaria alternata) is one of the most common foliar diseases of cotton (Gossypium spp.) and occurs in most cotton-growing regions of the world. Control of the disease through genetic resistance is not possible at present because no cotton cultivars with high levels of resistance to A. alternata are commercially available. In the past decade, the effectiveness of resistance-inducer salts against plant pathogens gives an environmentally friendly option for disease control. Therefore, the impact of salicylic acid on disease control, plant growth and some biochemical constituents of two cotton cultivars (Gossypium hirsutum L.), Golestan and Sahel under A. alternata stress, were evaluated. Materials and methods: Treatments, four levels salicylic acid (0, 0.05, 0.1 and 0.5 mM) and two level inoculation factor (control and pathogen) as a factorial experiment in a completely randomized design with four replications were studied in field condition. 20-day old cotton plants were sprayed with different concentrations of salicylic acid and the treatment were repeated two times at 14 days intervals. Effect of salicylic acid on the differences in growth traits (plant height and number of sympodial branch), yield and disease index in two cotton cultivars (Gossypium hirsutum L.), Golestan and Sahel, were evaluated. Also, changes of total phenol, peroxidase activity and malondialdehyde contents were measured by chlorometric analysis. Results: The results showed that the isolate of A. alternata tested in this experiment were pathogenic to cotton cultivars. Although, Golestan cultivar were more susceptible to alternaria leaf spot than Sahel cultivars. Foliar applications of salicylic acid have been shown to significantly affect yield, disease index, total phenol, peroxidase activity and malondialdehyde contents in two cotton cultivars. 5 mM salicylic acid by significant increasing total phenol contents and peroxidase activity, alleviated the malondialdehyde contents and oxidative stress lead to low disease severity in all cultivars. Yield and oxidative stress affected significantly in Sahel in comparison to Golestan cultivar. The relationship between disease index and yield and leaf phenol accumulation, peroxidase activity and malondialdehyde contents in relation to disease index in the presence of salicylic acid concentrations was described as regresional models. Conclusion: Overall, this research revealed that seedlings treatment with salicylic acid has provided most optimal performance against A. alternata infection and oxidative stress. Although, the effect was different in two cotton cultivars. Hence, using of salicylic acid as a biotechnologic approach be suggested for improve plant to alternaria leaf spot resistance.
