فصلنامه علوم زراعی ایران
سال بیست و پنجم شماره 3 (پیاپی 99، پاییز 1402)

Plants are exposed to various environmental stresses during their life cycle. Considering the essential role of crop plants in the production of food, fodder, oil and biofuels, it is important to evaluate their responses to environmental stresses. Plants have developed complex molecular systems to respond and adapt to environmental stress conditions such as drought, salinity, cold and heat during evolutionary processes. The response to abiotic stress is significantly different in species and even in different cultivars of the same species. Identification of plant responses to abiotic stresses has caused a great revolution in post-genome era. Physiological and molecular analyses have helped to better identify plant responses, and in this regard, Arabidopsis genome sequencing has played an important role. Quantitative phenotyping system of plants using imaging technology and its combination with information technology has facilitated the understanding of complex responses of plants to abiotic stresses. Studies on new regulatory mechanisms including use of small RNA molecules, chromatin modulation and genomic DNA modification, have enabled researchers to recognize complex plant molecular systems in response to abiotic stresses. Researchers have found that plants have types of sensors and signaling systems to respond to environmental changes and stresses. The molecular patterns of these signals are transmitted for the proper induction of the downstream molecular events. Obtaining necessary information related to DNA function at gene levels, RNA transcription and protein products, requires the use of various functional genomics methods such as next generation sequencing and genome editing, with large amounts of data. These data, which are essential information for all genes, including gene products and their functions, transcription levels, cis-regulatory elements and alternative splicing patterns, are obtained as a result of accessing the complete genome sequence. With progress in functional genomics methods, many genes related to stress tolerance can be identified and used to improve the level of tolerance of crops to environmental stresses. In this article, studies related to functional genomics for identification of complex response systems in crop plants that cause adaptation to abiotic stresses have been reviewed.

Knowledge of spatial variation in yield as well as the factors that affect it, will improve field management. Geostatistical methods are very effective in identifying and describing the distribution patterns of soil variation in the field. In this regard, this research was conducted to study the spatial relationship of some important physical and chemical properties of soil with bread wheat cv. Pishgam grain yield under the conditions of competition with wild barley using geo-statistical method.

In 2019-2020 cropping season, a field experiment was conducted in Isfahan, Iran in the form of a grid system with a distance of 2 × 2 meters. At each grid point, soil properties, bread wheat cv. Pishgam grain yield and wild barley density were measured and recorded. Experimental variograms, model fitting, kriging estimation and drawing maps for different traits were done using GS+ software. To describe the spatial correlation between two variables, a cross-semivariogram was employed. Spearman's correlation coefficients were also calculated using SPSS software (Ver. 16).

The results showed that soil properties in the field varied from one place to another and were seen as patches with different sizes and shapes on the maps. The lowest (1.6%) and the highest (23.7%) of coefficient of variation (CV) for the studied soil properties were related to pH and nitrogen, respectively. The results indicated that the distribution of wild barley was not even or random, but had a patchy or cumulative distribution pattern. The interpolated maps by kriging showed that the weed patches generally tended towards the edges of the field. Wild barley had a strong spatial correlation with nitrogen (N) and phosphoreous (P) of the soil, while this weed was found in soils with low amount of clay and potassium (K). The cross-semivariogram showed that bread wheat cv. Pishgam grain yield had strong spatial correlation with N, K, pH, clay and silt properties of the soil with correlation coefficient of 75.0, 83.2, 83.6, 94.1 and 78.6%, respectively within the distances of 6.1, 3.7, 4.7, 14.0 and 3.2 meters. The results of cross-semivariogram, estimation of Spearman's correlation coefficients and also comparison of maps showed the negative relationship between bread wheat cv. Pishgam grain yield and wild barley density in the field. Spatial correlation between weed density and grain yield was 86.9% within the distance of 14.0 meters.

In general, the results of this research indicated that the spatial variation of soil properties and also weed density caused patchy patterns of bread wheat cv. Pishgam grain yield in the field. Knowledge of the spatial distribution of soil nutrients and weeds density in the field can be useful for site specific management of the breat wheat crop.

Among the cereal crops, barley is known as the fourth most important crop on a global scale and provides about 50% of the calories needed in the world. This plant can even make up to 70% of calories in less developed countries, especially in Africa and Asia. Terminal drought stress, as one of the consequences of climate change, has significant negative effects on the crop plants’ growth and production. Considering the importance of barley as livestock feed and its role in food industry, development and introduction of drought stress tolerant barley cultivars is very important. To increase the levle of terminal drough tolerance, breeders should combine the improvement of grain yield along with high level of terminal drought tolerance. To reach this goal first step in this way is to select potential germplasm that have genotypic variation for drought tolerance.

Eighteen barley promising genotypes were evaluated for adaptation, grain yield  and yield stability under none-stress and terminal drought stress condtions (withholding irrigation from the 50% spike emergence stage)  using randomized complete blocks design with three replications in three research field stations; Varamin, Birjand and Yazd, Iran, in two cropping seasons (2020-21 and 2021-22). None-stress and stress experiments were carried out separately. In non-stress conditions, full irrigation was applied, and in terminal drough stress conditions, irrigation was withheld at the 50% spike emergence stage. The barley promising genotypes were selected from the advance barley grain yield comparison trial genotypes in the temperate zone stations of the country in the previous cropping season. After determining the grain yield in two conditions of none stress and drought stress, the stress indices including; MP, GMP, TOL, HARM, STI, YI, YSI, RSI and SSI as well as their correlation with grain yield were calculated using the iPASTIC program and the three-dimensional distribution diagram of genotypes in A, B, C and D ranges was drawn using Grapher software. Combined analysis of variance was performed to study genotypic variation and genotype × year interaction effect. Least significant difference (LSD) test was employed for mean comparison at the 5% propbabilty level. Different stability statistics as well as their relationships were calculated using Pearson correlation using STABILITYSOFT program.

The results showed that YI, HM, GMP, STI and MP indices can be used to select barley genotypes adapted and suitable for areas that are prone to terminal drought season stress. In non-stress areas MP, STI, GMP, HM, TOL and SSI indices can be used for selection of suitable and adapted cultivars. According to the biplot diagram, genotypes 2, 3, 11, 12 and 15 had higher grain yield and terminal drough tolerant. Considering mean grain yield, yield stability statistics, and standard deviation of the rank of each of these statistics, genotypes 11, 8, 3, 6 and 15 had higher grain yield stability.

Considering mean grain yield, all stability statistics and stress indices, genotype no. 11 with pedigree of GS679.82/SHYRI//LAUREL/4/CERISE/SHYRI//… /5/MALOUH//Aths/ Lignee686/6/Nik, genotype no. 8 with pedigree  of Anoidium//Alanda/Hamra-01/3/Lignee527/NK1272//JLB70-63/4/Nik, genotype no. 3 with pedigree of 82S:510/3/Arinar/Aths//DS 29/4/Sahra, genotype no. 6 with pedigree of Bgs/Dajia//L.1242/3/(L.B.IRAN/Una8271//Gloria'S'/3/Alm/Una80//....)/4/Sahra and genotype no. 15 with  pedigree of Ashar/Beecher/5/Lignee 527/Chn-01//Gustoe/4/Rhn-08/3/Deir Alla 106//Dl71/Strain 205 as superior genotypes that are suitable for cultivation in none-stress as well as terminal drought stress conditions in temperate agro-climate zone.

Climate change is a very serious threat to crops production in all regions around the world. Heat stress is a consequence of climate change that affects biochemical, physiological and molecular processes of crop plants, causing alterations in crop growth, development, and productivity. Terminal heat stress is the most widespread and type of heat stress in the world that limits crop productivity and ultimately food security. Sunflower is moderately tolerant to heat stress. It can tolerate higher temperatures without suffering from heat stress. However, sunflower is more susceptible to heat stress from early flowering to grain filling. Hence, it may be severely damaged when exposed to terminal heat stress. Biochemical and physiological responses in crop plants are modified under heat stress. It has been shown that tolerance to heat stress in crop plants is associated with an increase in antioxidant enzyme activities. The physiological and biochemical responses to heat stress vary among crop plant species and genotypes which can be used for development of cultivars with high temperature tolerance in crop plants.

This experiment was carried out in 2017-2018 growing season in Ahvaz, Iran, using as split-plot arrangement in randomized complete block design with three replications. Main plots consisted of three sowing date including; 11th November, 11th December and 11th Janauary, and five sunflower cultivars including; Qasem, Fantasia, Shams, Lakomka and Progress were randomized in sublpots. Sowing on 11th November was considered as normal sowing date, and sowing on 11th December and 11th January were delayed and late sowing dates, respectively. In the two latter sowing dates, flowering and grain filling periods were exposed to moderate and severe terminal heat stress.

Terminal heat stress in delayed and late sowing dates caused significant reduction in carotenoid content (27% and 56%, respectively), seed yield (30% and 32%, respectively) and oil yield (18% and 28%, respectively), but increased catalase (63% and 55%, respectively), peroxidase (107% and 56%, respectively) and superoxide dismutase (43% and 67%, respectively) enzyme  activities, carbohydrate concentrations (18% and 30%, respectively) and malondialdehyde concentration (46% and 98%, respectively), when compared to normal sowing date. There was significant differences among sunflower cultivars for most of studied traits. Lakomka cultivar with the highest values of biochemical and physiological indices such as chlorophylle content, antioxidant enzyme activities and carbohydrates concentration and with the lowest malondialdehyde concentration had the highest seed yield (1579 kg.ha-1) and oil yield (608 kg.ha-1) under terminal heat stress.

Exposure to moderate and severe terminal heat stress differently influenced physiological and biochemical traits in sunflower cultivars. The severity of terminal heat stress played an important role in the cultivars responses. Progress cultivar had the lowest reduction in oil and seed yield under terminal heat stress, however, cv. Lakomka showed highest seed and oil yield in all three sowing dates. Therefore, it can be concluded that cv. Lakomka is suitable for being sown in normal, delayed and late sowing dates due to least variability in its seed yield.

Oilseeds have high nutritional value and importance among agricultural crops for providing calories and energy needed by humans, and are the second food source in the world after grains. Since more than 95% of the vegetable oil consumed in Iran is supplied by imports, research in various agronomic practices, especially applied research on rate and application methods of fertilizers in oilseed crops is necssary. Camelina (Camelina sativa L.) is an annual plant and belongs to the Brassicaceae family. Biofertilizers are considered as new achievements in organic farming. Today, the use of biofertilizers with the aim of increasing soil fertility and producing products in sustainable agriculture is considered as an alternative to chemical fertilizers. Considering limited studies that have been done on Camelina (Camelina sativa L.) in Iran, the purpose of this research is to investigate the effect of combining nitrogen, phosphorus, potassium, sulfur and biofertilizers on the seed yield and yield components of this oilseed crop.

This experiment was conducted with the aim of investigating the effects of growth-promoting bacteria and chemical fertilizers on the yield of camelina. The experimental design was factorial arrangements in randomized complete block design with 18 treatments and three replications in 2021-2022 at Research Farm of Shahid Chamran University of Ahvaz, Iran. Experimental treatments included; nitrogen fertilizer levels based on chemical fertilizer (N0-P0-K0-S0) (C1) and (N50-P50-K40-S100)(C2) and (N100-P100- K80- S200)(C3) and biological fertilizer levels or growth promoting bacteria at six levels included: no inoculation/ control (B1), Nitroxine (B2), Phosphate (Barvar2) (B3), Thiobacillus (B4), Nitroxine+Phosphate (Barvar2) (B5) and Nitroxin + Phosphate (Barvar2) + Thiobacillus (B6). Camelina cv. Soheil was used in this experiment. Urea fertilizer was used as nitrogen, potassium sulfate as potassium, triple superphosphate as phosphorus, and bentonite sulfur as sulfur source. Camelina seeds were inoculated with biological fertlizers.

Results showed that the highest seed yield (2120 kg.ha-1) and biological yield (5803 kg.ha-1) obtained in Nitroxin + Phosphate (barvar2) treatment. In all three levels of chemical fertilizers, biological fertilizers increased seed oil content. The highest seed oil content (45.1%) was obtained in the control treatment without chemical fertilizers and application of Nitroxin. Compared to the control (no inoculation), biological fertilizers had less effect on camelina plant traits, but in combination with chemical fertilizers, they improved the growth and seed yield of camelina.  

According to the results of this experiment, the best fertilizer treatment to increase the seed yield of camelina was the combined treatment of Nitroxin fertilizer + Phosphate (Barvar2) in all three levels of chemical fertilizers.

Different environmental and genetic factors such as variety, climate, soil and agronomic practices factors are effective in increasing root sodium content and reducing the yield and quality of sugar beet roots. Therefore, in this research, using meta-analysis, the effect of these factors has been determined and agronomic practices for reducing the sodium content of the roots and increasing the quality of produced sugar. The purpose of this meta-analysis was to determine management practices with significant effects on yield and quality of sugar beet roots in Iran.

This study was conducted on data collected from the experiments carried out at Sugar Beet Seed Institute (SBSI) in Karaj and Agricultural and Natural Resources Research and Education Center in different provinces in Iran for the period of 1997 to 2020. Data were analyzed from 33 final technical reports of research projects of the the experiment that had appropriate agronomic management treatments. The data and information of these reports were created as a database containing 450 rows in 26 columns. The corresponding data to the investigated treatments were considered from the database and then the reaction ratio, average of the reaction ratio, standard deviation and the significant effect of each factor on sugar beet root yield and quality traits were determined.

The results of meta-analysis of agronomic practices factors in the period of 23 years of research showed that lack of irrigation in the early season after crop establishment caused significant decrease in root sodium content (α=0.05). The effects of row and plant spacing, land preparation methods, crop rotation, late season moisture stress, mild and severe drought stresses, on root sodium content were not significant. Crop rotation caused significant increase in root, sugar and white sugar yields by 17.5%, 23.7% and 26.7%, respectively. Early and late season drought stresses and severe drought stress caused significant decrease in root yield by 21%, 42%, 33%, respectively. Reduction in white sugar yield were 18%, 43% and 32% under above mentioned drought stresses conditions.

The crop rotation of legumes-wheat-sugar beet compared to the conventional rotation of wheat-sugar beet increased sugar beet root yield by about 20%. The best method of soil preparation was detrmined as plowing or using sub-soiller in autumn and carrying out other operations including disc and furrower in spring. Increasing the planting row spacing to 60 cm caused significant decrease in root, raw sugar and white sugar yields by 6% to 10% due to the decrease in plant density. Changing plant spacing within rows from 20 cm to 15 cm did not have significant effect on sugar beet traits. Water deficit at the early season and after the establishment of sugar beet crop decreaseed the sodium content of sugar beet roots during the season, and also reduced root, sugar and white sugar yields, but the amount of yield reduction was lesser than drought stress at the end of season. Therefore, it is recommended to continue irrigation during the sugar beet technological ripening stage. Irrigation could be applied after 70% decrease of the soil moisture content to reduce water use without any significant reduction in root yield.