جستجوی مقالات مرتبط با کلیدواژه « drought tolerance » در نشریات گروه « کشاورزی »

Cross breeding processes including targeted crossings to increase drought tolerance, can be considered as a safe and permanent solution to reduce the harmful effects of drought stress on plants. Therefore, two issues of pistachio as a strategic crop in the country and location of Iran in arid and semi-arid region necessitated research in order to achieve rootstocks drought-tolerant hybrids are necessary.

The experiment was conducted as factorial based on a Completely Randomized Design with four replications in the research greenhouse of Gorgan University of Agricultural Sciences and Natural Resources during 2018-2019. The treatments were consisted of 10 pistachio genotypes Ahmad Aghaei, Akbari, Sorkheh Hosseini, Garmeh, Fandoghi and interspecific hybrids (Ahmad Aghaei ×Integerrima, Akbari ×Integerrima, Sorkheh Hosseini × Integerrima, Garmeh × Iintegerrima and Fandoghi × Integerrima) and three levels of drought including control (field capacity), mild stress (65% of field capacity) and Severe stress (30% of field capacity) were applied on 3 months old the seedlings for 84 days.

According to the results, fandoghi genotype showed a higher malondialdehyde concentration in leaves (280.23 %), while the hybrid genotypes of Sorkheh Hosseini × Integerrima, Ahmad Aghaei ×Integerrima and Akbari × Integerrima showed a lower malondialdehyde concentration in leaves by 70.18, 76.70, 81.03 % respectively compared to the control. Several osmotic mechanisms are carried out by plants, especially pistachios, in stressful conditions to reduce the effects of drought stress. In fact, these mechanisms have enabled plants to withstand the damages caused by drought and have made plants able to recover their biochemical and physiological functions faster after removing the stress factor. For example, a general physiological mechanism adopted by plants to cope with abiotic stresses is the production of large amounts of low molecular weight, water-soluble, non-toxic organic compounds even in high amounts called osmolytes. One of the most important of them is proline. Therefore, the genotypes with higher amount of proline can be more tolerant to drought conditions. The next osmolyte is glycine betaine, which has a significant protective role in the stability of enzymes and the structure of plasma membranes when faced with drought stress. Therefore, glycine betaine plays a significant role in the resistance of plants to stress through the protection of enzymes, the photosynthetic apparatus, the elimination of free radicals, the preservation of membrane integrity, the protection of large molecules, and as a non-toxic compatible osmolyte. It has an environment. Carbohydrates also increase membrane stability in response to drought stress. Therefore, the accumulation of carbohydrates in the osmotic responses of plants is one of the factors that can prevent disorders in the cell membrane. In addition, phenols are also one of the antioxidant mechanisms of plants in drought stress conditions, because such compounds act as scavengers of reactive oxygen species and thus stabilize membrane, cells and prevent lipid peroxidation. Malondialdehyde is also a decomposition product of unsaturated fatty acids and hydroxides and is used as a suitable marker for lipid peroxide. Therefore, the amount of malondialdehyde obtained from the peroxidation of membrane lipids is used as an indicator for oxidative damage in most cases.

Based on the results of the present research, it seems that it is possible to use the hybrids of Sorkhe Hosseini × Integerrima, Ahmad Aghaei × Integerrima, and Akbari × Integerrima as drought-tolerant genotypes in dry areas. Therefore, based on the results of the present research, it seems that the plants in question can be used as drought tolerant genotypes in arid regions.

The water deficit is one of the most important problems in rice cultivation, particularly when the decrease in rainfall and dry season affects its vegetative growth and grain yield. Drought stress is known as one of the most effective factors of yield reduction in crops. Identifying and introducing tolerant genotypes is a good way to cope incompatible environmental conditions. For easier evaluation of genotypes under drought conditions and identification of drought tolerant genotypes, various indices have been suggested as criteria for selection of genotypes based on their yield under stress and non-stress conditions. The present study was conducted to evaluate some rice genotypes under drought stress conditions as well as to introduce drought tolerant genotypes using important tolerance and sensitivity stress indices.

This experiment was conducted in split plots based on randomized complete block design with three replications in Azadshahr, Golestan province, Iran. The main factor included two irrigation levels (drought stress and flooding as control) and the sub-factor included eight rice varieties. The experimental plots were three m2 with a distance of one m from each other. After randomly assigning the treatments to the experimental units, transplanting was done as four plants per pile. Each genotype was cultivated in six two-meter rows with a distance of 25 × 25 cm. Irrigation of the experimental field under both stress and non-stress conditions until the tillering stage of the genotypes was conducted as flooding. Then, under stressful conditions, irrigation was carried out from 40 days after transplanting (maximum tillering stage) until the end of the cropping season at an interval of 25 days, which according to the climatic conditions of the studied region, irrigation was done only once in stressful conditions. From the six rows planted in each plot, one row from around each plot was removed as border and the second to fourth rows were selected for sampling. After measuring traits and calculating different indices, the data were analyzed by SAS software. Two-dimensional biplot diagram was also drawn by STATGRAPHIC software.    
Research

The results of analysis of variance showed a significant difference between the genotypes for all studied traits under both drought stress and flooded (control) conditions. Comparison of means showed that the highest average grain yield under both control and stress conditions belonged to Fajr, IRAT216, Sang-Jo, and Sang-Tarom Gerdeh genotypes, and the lowest grain yield belonged to the Sepidrood variety. The results of the correlation coefficients showed that grain yield in control conditions had a positive and significant correlation with mean productivity (MP), geometric mean productivity (GMP), harmonic mean (HARM), and drought tolerance (TOL) indices, respectively, and the highest correlation was observed between grain yield and MP index (r = 0.918). Also, under drought stress conditions, grain yield showed a high correlation with the harmonic mean (HARM), geometric mean productivity (GMP) and mean productivity (MP) indices, the highest of which was related to harmonic mean index (r = 0.933). The results of principal component analysis showed that 94.31% of the total variation between data was justified by the first and second principal components. Cluster analysis based on drought stress indices separated rice genotypes into three groups, and the genotypes in the first cluster had the highest drought tolerance.

The results of biplot analysis and correlation between stress indices indicated that GMP, MP, and HM indices were the best indices for selecting high-yielding genotypes under both stress and non-stress conditions in this experiment. Based on these indices and biplot diagram, Fajr, Sang-Tarom Gerdeh, Sang-Jo, and IRAT216 genotypes were identified as high-yielding and drought-tolerant genotypes, and Sepidrood and Gharib Siah Reyhani varieties as low yielding and drought sensitive genotypes.

As one of the most important cereals, bread wheat is an essential part of food security in the world, which supplies one-fifth of the total calories of the world population. Nowadays, the yield of wheat has been affected by climate change-driven drought as one of the most important abiotic stresses that has become an important threat to food security in the world. Root and stomatal traits are especially important in breeding plants to withstand drought stress. Stomata play a key role in controlling carbon dioxide uptake and water loss through transpiration. Therefore, stomatal characteristics are used as indicators of water status and plant growth, especially in drought stress conditions. Having a wide range of physiological and morphological characteristics, roots play an essential role in absorbing water and nutrients. They are also the first organ that sends signals to control the stomata in response to dryness. Therefore, the difference in the structure of the root system can cause the difference between the performance in different cultivars. This study was conducted to investigate stomatal characteristics and their relationship with the root system and plant performance in 24 bread wheat lines and cultivars.

To investigate the relationship between stomatal dimensions and density with the root system, an experiment was conducted on 24 bread wheat genotypes in the form of a randomized complete block design with three replications in the rainfed conditions of the research farm at Zanjan University Faculty of Agriculture in the crop year 2018-2019. In this experiment, PVC pipes were used to study the root system. Twelve seeds were planted in each tube, which were thinned to seven after germination. In each experimental unit, there were two tubes for each genotype, one of which was used to evaluate traits and final yield, and the second tube was used for root studies. Stomatal traits, including the length and width of stomata and number of stomata per unit area, root traits including root length, root diameter, root volume, root surface, and root biomass, and seed yield were measured in the end. The resulting data from the measured traits were analyzed in the form of a randomized complete block design, and the averages were compared using the LSD method. The data were analyzed using multivariate statistical analyses, including regression analysis, path analysis, and factor analysis, and cluster analysis was used to group genotypes. Statistical calculations were done using SAS 9.0 and SPSS 21 software.

The results of analysis of variance and mean comparison showed high variability among genotypes for all measured traits. The results of the mean comparison of genotypes showed that genotypes 2, 5, 8, and 16 had the highest yield, and genotype 23 had the lowest yield among the examined genotypes. The highest number of stomata on the upper and lower leaf surfaces belonged to genotypes 5 and 2. In terms of root traits, the highest diameter, volume, length, root surface, and root dry weight at a depth of 0-25 cm were recorded for genotypes 2, 3, 18, and 5, respectively. There was a high and significant correlation between the yield and the number of stomata on the upper and lower leaf surfaces, the length and width of  the stomata on the upper leaf surface, diameter, volume, dry weight, and root surface at a depth of 0-25 cm in the soil. Based on the results of stepwise regression analysis, two variables, the number of stomata on the lower leaf surface and root dry weight at a depth of more than 25 cm explained 91.4% of the changes in grain yield. According to the results of the causality analysis of the number of stomata on the lower leaf surface, the most direct effect had a positive effect on seed yield. The results of factor analysis grouped the studied traits into three factors with 82.48% variability justification. The shares of the first, second, and third factors to explaining data changes were 48.86%, 24.62%, and 8.99%, respectively. Based on the plot obtained from factor analysis, genotypes 2, 5, 8, and 16 had high values for the first and second factors. According to the coefficients of the factors, it can be claimed that the genotypes located in this area have high performance, a high number of stomata, and strong root traits, which were found at the soil depth of 0-25 cm. For this reason, these are the genotypes that could produce high yields by absorbing water from the surface layers of the soil by having a large number of stomata and carrying out more photosynthesis. Moreover, the investigated genotypes were divided into three groups from cluster analysis by the ward method and Euclidean distance. Genotypes 2, 5, 8, and 16 were placed in the first group and had the highest mean values for grain yield traits, number and width of stomata on the upper and lower leaf surfaces, and root traits including diameter, volume, and dry weight at a soil depth of 0-25 cm, and root diameter at a depth greater than 25 cm. The lowest values for stomatal length were observed in both leaf surfaces. These were the best genotypes for cultivation in dry conditions.

A strong superficial root system can provide the plant with water from scattered rains that occur with low frequency at the end of the growth period. On the other hand, the increase in the number of stomata along with their smaller size reduces leaf pores and enables a faster response of the stomata, and the rapid response of the stomata maximizes water use efficiency. Therefore, having a strong superficial root system along with high stomatal density can increase seed yield in dry conditions.

 Drought is one of the most important global threats to food production, in addition to that, climate change and the increase in the global population also widen the dimensions of this problem. One of the ways to solve this problem is to create new cultivars with greater tolerance to drought stress. Wheat has been one of the most important sources of human food all over the world and it is used in various food products and processing industries. Wheat together with rice and corn provide more than 60% of calories and protein needed for human nutrition. In areas like Iran, where most of the rain occurs in winter and early spring, wheat will face water shortage and drought stress at the end of the growing season. In crops, one of the effective methods that can minimize the effect of this phenomenon in combination with other methods of water deficit management is the use of high-yielding and drought-tolerant cultivars. Despite the numerous scientific sources published in this field, there are still many gaps in these studies, so studying the effects of drought stress is always a research priority. Ilam province, as one of the irrigated wheat production areas, suffers from the lack of cultivars that are resistant or tolerant to low irrigation conditions, so investigating the response of different wheat genotypes in low irrigation conditions as low input production systems is very important and is addressed in this study. 

In order to evaluate some bread wheat genotypes under normal and drought stress co ditions, 36 wheat genotypes were evaluated in the form of a randomized complete block design in three replicates in the crop year of 2019-2019 in Darehshahr city located in Ilam province. The examined traits include spike length, spike number per plant, spike length, peduncle length, sub-peduncle axis, flag leaf length, flag leaf width, number of stem nodes, plant height, number of spikes per plant, number of seeds per spike, number of seeds per plant. plant, number of tillers, hundred seed weight, single plant seed weight and seed yield. Based on performance under stress (Yp) and normal (Ys), drought tolerance indices such as average productivity tolerance index, harmonic mean, geometric meanproductivity (GMP), stress sensitivity index, stress tolerance index, performance stability index (YSI) and Relative Stability Index (RSI) and Performance Index (YI) were calculated. The mean comparison test was performed using Duncan's method and using R software. Simple correlation (Pearson), decomposition into components, decomposition into factors were also performed between the tested traits. SAS 9.1 statistical software was used for statistical analysis of traits. 

The results of the analysis of variance in drought and normal stress conditions showed that there was a significant difference between genotypes in all traits at the probability level of 1%. The most important significant correlation coefficient in both conditions between seed yield was related to the seed weight of a single plant and the number of seeds per plant. Considering the high and significant correlation of grain yield under stress and non-stress conditions with drought tolerance indices, higher productivity indices, geometric mean productivity (GMP), geometric mean  and stress tolerance index  as the best indicators. were chosen. It seems that in order to evaluate stress tolerance, the selection of genotypes should be based on several indicators. Factor analysis at the drougth stress condition indicated that the two first factors expalined a total of 97. 57% of the variance. The first factor was called the performance stability factor and the second factor was named theStability Factor. The biplot diagram also showed that the genotypes of no. 13 and 47 were placed in the vicinity of the ranges related to drought resistance indices (STI, MP, GMP, and HM) and were introduced as superior genotypes. 

According to the data obtained from analysis of variance in both normal and drought stress conditions, the genotypes were significant in terms of all traits. The significance of the studied traits indicates the existence of diversity between genotypes in terms of the studied traits, and some of these traits can be used to evaluate stress tolerance. The best genotypes had the best averages for peduncle length of genotype 33, for the number of seeds per plant of genotype 5, for seed weight of a single plant and seed yield of genotype 1. The heat map shows the relationship between drought tolerance based on different yield and drought stress toleranceindices. Considering the high and significant correlation of grain yield under stress and non-stress conditions with drought tolerance indices, average productivity indices, GMP, geometric mean and stress tolerance index were selected as the best indices that are able to distinguish tolerant genotypes from other Screen the genotypes. The yield index (YI) had the highest correlation coefficient with grain yield under stress conditions. Based on biplot results, genotypes No. 13 and 47 were the most tolerant genotypes under drought stress conditions more than other genotypes and were introduced as superior genotypes.

Drought is one of the most important abiotic stresses that affects the growth and production of crops. Therefore, the need to breed cultivars that have high compatibility and low water demand is strongly felt. This study was conducted to evaluate the effect of irrigation levels on cultivars and promising lines of cotton, to use the stress tolerance and susceptibility indices for identification and selection of drought tolerant genotypes, as well as to compare cotton promising lines (KD-92-11, KD-92-17 and KD-92-19) with control cultivars of Aria and Ghoze Ghermez (which are suitable for cotton growing areas in Khorasan and Isfahan provinces). For this purpose, an experiment was performed according to the split-plot design with three replications under four irrigation levels (normal, 25, 50 and 75% deficit irrigation compared with normal) in 2020 at Kashmar. The results showed that the irrigation level had a significant effect on all traits except for keel percentage and earliness. The trait of single boll weight decreased by 7, 24 and 32% at the irrigation levels of 25, 50 and 75%, respectively, compared to the normal regime. In the same conditions, the total yield also decreased by 3, 34 and 48%, respectively. There was a significant difference between genotypes in terms of all studied traits (except for keel percentage and earliness) and drought tolerance and susceptibility indices, which indicates high genetic diversity among the genotypes and can be effective in improving selection in the breeding programs. Mean comparison of traits in the four irrigation levels showed that with the reduction of irrigation levels from 25 to 75%, the average of all traits decreased and the greatest decrease was observed in the 75% moisture regime. In each of the four irrigation levels, control cultivars were superior to promising lines in terms of single boll weight, second harvest yield, and total yield. However, in terms of the traits of keel percentage, early maturity, number of vegetative and reproductive branches, and number of open bolls, the promising lines were superior to the control cultivars. In each of the three moisture stress regimes, the control cultivars of Ghoze Ghermez and Aria did not show any difference in stress tolerance, but compared to hybrids, the promising lines had between 5 and 25% more stress tolerance in terms of various traits.

Drought is one of the most important abiotic stresses that limit the growth and production of agricultural plants and affects all morphological, physiological, biochemical and metabolic aspects of plants (Blum, 2011). Changing the cultivation pattern and identifying heat and drought tolerant plant species and cultivars with high adaptability and low water requirements are among the main objectives of plant breeding in arid and semi-arid regions of the world. Cotton, as a strategic plant and the most important fiber plant, is one of the most important agricultural plants that provides the connection between the two sectors of agriculture and industry and plays a valuable role in the economy of some countries. It shows greater tolerance to abiotic stresses than other major crops. However, extreme environmental conditions such as drought are severe threats to the sustainability of cotton crops in dryland agriculture and affect the growth, productivity, and quality of cotton fibers (Barzali et al., 2016). This study was conducted to evaluate the effect of irrigation levels on cultivars and promising lines of cotton, to identify and select the drought-tolerant cultivars, and to compare the cotton lines with control cultivars.

In this study, three promising lines resulting from the crossing of Herbaceum and Arboreum species (KD-92-11, KD-92-17 and KD-92-19) along with two diploid control cultivars (Aria and Ghoze Ghermez) were cultivated according to the split-plot design with three replications at four irrigation levels (normal or control, 25, 50 and 75% deficit irrigation compared with normal) in 2020 at the field of the Research and Training Station of Agriculture and Natural Resources in Kashmar. Then, in order to select for drought tolerance, a set of morphological traits (height, number of vegetative and reproductive branches, number of opened and closed bolls, and crown diameter) and agricultural traits (single boll weight) along with yield, earliness and keel percentage were measured. Some drought tolerance and susceptibility indices were also calculated based on the yield of genotypes under normal and drought stress conditions.

Drought stress had a significant effect on all traits except for keel percentage and earliness. There was a significant difference between the studied genotypes in terms of all traits (except for keel percentage and earliness) and indices, which indicates high genetic diversity among the genotypes. The mean comparison showed that with the reduction of irrigation level from 25 to 75%, the average of all traits decreased, and the greatest decrease was observed in the 75% moisture regime. In all four moisture regimes, control cultivars were superior to the lines in terms of single boll weight, the yield of the first cut, the yield of the second cut, and total yield. However, in terms of the other traits, promising lines were superior to the control cultivars. In all three moisture stress regimes of 25, 50, and 75%, the control cultivars of Ghoze Ghermez and Aria did not show any difference in stress tolerance, but compared to the lines, they had more drought tolerance.

Based on the results of this study, there was high genetic diversity between the studied genotypes, which can be used in the breeding programs. Drought stress negatively affected all traits and reduced their diversity. Most significant decrease was observed in the 75% moisture regime. In all of the moisture environments, control cultivars were superior to promising cotton lines in terms of yield and single- boll weight. However, promising lines were superior to control cultivars regarding the remaining traits. Moreover, in all three moisture stress regimes, the control cultivars of Ghoze Ghermez and Aria did not show any difference in terms of stress tolerance, but compared to the promising lines (KD-92-11, KD-92-17, and KD-92-19), they showed more drought tolerance.

In order to compare 25 genotypes of bread wheat in terms of morpho-physiological and biochemical traits, an experiment was conducted in a randomized complete blocks design with three replications in the rainfed and irrigated conditions at Razi University, Iran, in 2016-2017. GT-biplot was used to evaluate genetic diversity and to identify stable genotypes with high yield and drought tolerance. Combined variance analysis showed that there was high variability among genotypes for the most of traits. Examining the correlation of traits in two environmental conditions showed that morpho-physiological traits; especially yield components, were the most related to yield. The results of the GT-biplot method showed that the first and second principal components explain 41.7% and 40.1% of the total changes in rainfed and irrigated conditions, respectively. Based on the GT-biplot analysis diagrams of genotypes 10, 15, 6, 13, 2, 14, and the Pishtaz cultivar in terms of physiological traits, yield and its components and the traits related to stem and spike in irrigated conditions, and genotypes 10, 15, 6, 18, and 17 in terms of biochemical traits, yield and its components, and traits related to stem and spike in rainfed conditions were recognized as superior genotypes. The genotypes 2 and 6 in irrigated conditions and the genotype 6 in rainfed conditions had the lowest genotype×trait interaction. Finally, the genotypes 10, 15, and 6 were superior in two environmental conditions and the genotype 6 had the least interaction effect in both conditions. Therefore, these genotypes can be used in breeding programs.

Barley (Hordeum vulgare L.) is known as the fourth most important grain crop in the world. Drought stress is also one of the main factors that reduce the growth and yield of barley, and grain yield is directly related to the morphological characteristics of the flag leaf.. In order to identify the main and epistatic genomic regions and investigate their interaction with the environment for morphological traits related to flag leaf, including length, width, area, and flag leaf sheath length, an experiment was conducted with 136 doubled haploid lines of barley along with their parents 'Nure' and 'Tremois' using an alpha lattice design with two replications under normal and drought stress conditions at the Zabol Agricultural Research Station, Iran, in 2015-16 growing season. The genetic map of the target population comprised 543 markers (including DArT, SSR, SNP, and AFLP markers) for the QTL analysis. In this study, single-locus and two-locus QTL analyses were performed using the composite interval mapping (CIM) and mixed-model based composite interval mapping (MCIM) methods, respectively. Based on a single-locus analysis, five QTLs were identified, including three putative QTLs, Q1FLW-1H.SZ, Q1SHFLL-1H.NZ and Q2SHFLL-1H.NZ at bPb-6343-bPb-8081, bPb-1419-bPb-9180, and bPb-9108-bPb-6343 marker intervals, and two suggestive QTLs, on chromosomes 1H and 5H for the traits of flag leaf width (FLW, cm) and flag leaf sheath length (SHFLL, cm). Based on a two-locus analysis, eight additive (M-QTL) QTLs and 15 pairs of epistatic effects (E-QTL) were detected for different traits, among which two pairs of epistatic QTLs for the FLW trait showed significant QTL × environment interactions (AAEI). All detected M-QTLs for flag-leaf-related traits across two environments, without additive × environment interactions (AEI), were identified as stable QTLs, and the highest number of stable QTLs was associated with chromosome 1H. In this study, drought stress-tolerant QTLs were identified in all barley chromosomes except chromosome 2H. Most of the QTLs associated with the investigated traits in the Nure/Tremois population in the present study have not been reported previously and, therefore, are novel. The stable and putative QTLs controlling flag-leaf-related traits in this study, along with the markers linked to these QTLs, can be utilized in marker-assisted selection (MAS) and gene pyramiding breeding programs after confirmation and validation in different environmental conditions and genetic backgrounds to create high-yielding and drought-tolerant barley cultivars. Additionally, these findings will accelerate the understanding of the genetic relationships among spike-related traits at the molecular level.

This study aims to prepare a paternal parent (pollinator) tolerant to drought stress using full sib families in the Karaj region in Motahhari's station of Sugar Beet Research Institute in 2015 in conditions without stress (based on water needs) and drought stress. For this purpose, an experiment in the form of a split-plot design was conducted with 13 full sib families, two drought-tolerant cultivars (IR7) and (stable), and a normal genotype (191) as control cultivars, with the main factor consisting of two levels (irrigation with drought stress and irrigation without stress) and the sub-factor of all sister families and control genotypes implemented in four replications for one year. After emergence, irrigation treatments were used in both instances (at least twice irrigation). At a probability threshold of 1% and 5%, respectively, the results revealed a statistically significant difference between irrigation treatments for root production and gross sugar output. As a result, a stable cultivar has the largest production of these two qualities.Furthemore, in the two modes of regular watering and stress, the mean root output in the examined families revealed a significant difference at the one percent probability level. Drought stress (SI = 0.72) lowered root and sugar yields. Cultivar 3, origin S1-930637, also has the greatest percentage of gross sugar and the highest drought tolerance index.

Drought stress is one of the most limiting abiotic stresses affecting growth, production and survival of plants in many areas of the world, and is expected to intensify considering the trend of climate change. Grass species are important for the sustainability of agricultural systems, forage resources for animal farming and landscapes. Grass species adapt to water deficit by different morphological and physiological responses such as changes in the root growth, photosynthetic pigments, activation of antioxidant enzymes and accumulation of osmotic compounds as well as other specific characteristics, such as summer dormancy, post drought recovery, and persistence, which lead to their drought adaptation following suffering prolonged water stresses. Summer dormancy is one of the important drought avoidance mechanisms in cool-season perennial grasses which lead to decreasing of forage yield during hot and dry summer, and increasing of recovery and survival potential of grasses after suffering from a prolonged drought stress. The results of the studies have indicated that most of plant traits in grasses have high narrow-sense heritability and positive correlation with drought tolerance, therefore can be considered as effective and useful indices in identification and selection of drought tolerance cool seasons grasses genotypes. Using molecular techniques and tools along with the conventional breeding methods in grasses have increased the accuracy and speed of breeding programs for producing drought tolerant cultivars. These techniques in grasses have been instrumental in assessing genetic diversity, molecular identification of paternal parents in the open pollinated populations, determining the gene loci, genome sequencing, and genes associated with drought tolerance.

A bread wheat breeding line that led to release of Tallaei cultivar introduced from International Research Center for Maize and Wheat (CIMMYT) to Iran through an international nursery in 2009 and was evaluated in a primary trial in Islam Abad-Gharb research station and due to its favorable characteristics was selected for further evaluation. This line showed grain yield of 6967 and 5370 kgha-1 under normal irrigation and terminal drought conditions, respectively, while mean grain yields of four check cultivars: Parsi, Sivand, Bahar and Pishtaz for those two conditions were 6857 and 3850 kgha-1, respectively, Aforementioned line showed grain yield of 4851 kgha-1 in advanced yield trial of temperate regions breeding program under water deficit conditions compared to 4631 khha-1 of drought tolerant check cultivar "Sirvan" in three locations, hence selected for final evaluation in adaptation trial. Grain yield of this line which was presented as M-91-18 at the adaptation trial was 7563 and 6385 kgha-1 against 8022 and 6200 kgha-1 of Parsi check cultivar under normal and water stress conditions, respectively, during two cropping seasons 2012-13 and 2013-14. This line showed overall mean grain yield, of 9583 and 8042 kgha-1 in normal irrigation and water deficit conditions under extensional farmer fields, respectively. For these two conditions check cultivar Parsi showed 7875 and 6828 kgha-1 records. Grain yield potential of this line was recorded as 10070 and 10670 kgha-1 in Alborz and Kermanshah farmers' fields, respectively. According to the latest evaluations the response of this line to yellow and leaf rusts was moderately resistant under severe artificial infection. Wheat line M-91-18 has considerable earliness and good bread making quality and based on its good agronomic characteristics in 2017 this line was released as Tallaei, for cultivation under normal and terminal moisture stress conditions in temperate agro-climatic regions.

Oilseeds are undoubtedly one of the most strategic agricultural products; their production is of basic needs for food security in any society. Sunflower with the scientific name of Helianthus annuus L. is an annual, monoecy, dicotyledonous plant that belongs to composite family. This genus consists diploid, tetraploid and hexaploid species, and common sunflower is a diploid species with a base chromosome number of x=17. Sunflower is grown mainly for its edible oil. Environmental stresses such as drought, salinity, unusual temperatures, heavy metal and UV radiation are serious threats to plant growth, metabolism and productivity. In recent years, astonishing advances in biotechnology, genetic engineering, and computer science have made breeding programs much faster, more accurate, and more efficient than ever before. New techniques, if properly incorporated into breeding programs, can dramatically increase the speed and accuracy of these programs and can reduce costs by an extraordinary amount. In this article, while briefly referring to conventional breeding methods, new methods and their application in sunflower breeding are discussed. In the last 10 years, the science of genomic has expanded the genetic information of quantitative traits, and marker assisted selection has become a practical tool.

Torabi wheat cultivar introduced to iranian wheat breeding program through an international nursery from CIMMIT (28th SAWSN) in 2010 and was evaluated under terminal drought stress implemented from the flowering stage in 2010-2011 cropping season. Then in 2011-2012 cropping season it was tested in the preliminary regional wheat yield trial under terminal drought stress in Karaj and was selected based on its average grain yield of (4878 kgha-1) compared to the average grain yield of (3939 kgha-1) Parsi check cultivar. This cultivar was further studied in the advanced regional wheat yield trial in the temperate regions of the country during 2012-2013 and with average grain yield of 6634 kgha-1 under drought stress condition compared to 6073 and 6768 kgha-1 yields of check cultivars Parsi and Sirvan, respectively, was selected for evaluation in the adaptability and yield stability. The average grain yield of Torabi (line M-92-20) in adaptability experiment during the years 2013-2015 under drought stress conditions was 6516 kgha-1 compared to 6110 kgha-1 of Sirvan check cultivar and 5697 kgha-1 of Parsi check cultivar and also its total grain yield mean was 3% higher than the average grain yields of all genotypes. Due to the resistant reaction of the line M-92-20 to stripe and leaf rust diseases, as well as the early maturity and very good bread making quality, this line was selected for evaluation in the on-farm trials in farmer’s fields. Overall in farmer’s fields, this line had grain yield mean of 8637 kgha-1 under normal irrigation, and 5672 kgha-1 under water deficit conditions compared to the average yield of check cultivars with 6150 kgha-1 under optimal conditions and 5104 kgha-1 under water deficit conditions.

In the present study, chlorophyll fluorescence technique was used as a non-destructive tool to compare the drought tolerance of rootstocks and to estimate the performance of photosystem II. In this regard, this research was conducted as a factorial Completely Randomized Design with four replications in the research greenhouse of Gorgan University of Agricultural Sciences and Natural Resources during 2018-2019. The experimental factors were consisted of ten pistachio rootstocks of Ahmad Aghaei, Akbari, Sorkheh Hosseini, Garmeh, Fandoghi and interspecific hybrids of Ahmad Aghaei × integerrima, Akbari × integerrima, Sorkheh Hosseini × integerrima, Garmeh × integerrima and Fandoghi × integerrima, and three levels of drought stress including control (Field Capacity), mild stress (65% of Field Capacity) and Severe stress (30% of Field Capacity) were applied on 3 months old seedlings for 84 days. The results showed that with increase in drought levels, the maximum fluorescence (Fm), variable fluorescence (Fv), maximum efficiency of photosystem II (F / Fm) and seed biomass were decreased and minimum fluorescence (F0) was increased. The highest amount of these indices except F0 index was observed in the control and there was a significant difference with severe stress. Based on the results, different rootstocks showed different physiological responses in response to the applied stresses. Sorkheh Hosseini × Integrima, Ahmad Aghaei × Integrima and Akbari × Integrima hybrids showed the highest and the Fandoghi rootstock showed the lowest quantum performance (photosystem II) compared to other rootstocks. In terms of fresh and dry weight of stems, roots and leaves, Sorkheh Hosseini × Integrima, Ahmad Aghaei × Integrima and Akbari × Integrima hybrid rootstocks were less affected by drought stress. Based on the results of the present study, it seems that these three rootstocks can be used as containing drought tolerant genes for breeding cultivars with high yield potential in arid regions.

Germination is one of the most important stages of plant growth that determines the durability, establishment and final yield of crops and in regions that due to drought conditions the growth of plant encounters with problem, improving germination traits count as one of the important breeding strategies. The present study was designed to determine the effect of different levels of osmotic stress on germination and seedling traits of some bread wheat cultivars cultivated in cold regions of Iran.

In order to investigate the effect of different levels of osmotic stress on germination characteristics of bread wheat cultivars cultivated in cold regions of Iran, a factorial experiment was conducted based on a completely randomized design with 3 replications in which, the first factor consisted of 20 bread wheat cultivars (including rain fed cultivars as well as end-of-season water stress tolerant varieties) and the second factor consisted of 3 levels of osmotic stress (non-stress, -3 and -6 bar stress). Seedling traits such as coleoptile length, shoot length, shoot weight, root length, root weight, root / shoot ratio, root growth angle, germination speed and the germination stress index (GSI) were evaluated. For the experiment concerning the yield comparison, 20 cultivars mentioned above were compared under non-stress and terminal drought stress conditions.

The results showed that the ratio of root/shoot length and weight and shoot weight had the highest sensitivity and the lowest number of roots to osmotic stress. Increasing root length as root weight decreased with increasing stress showed that roots became longer and thinner due to stress. Among the genotypes, Saein, Zare, Pishgam, Sadra, Baran and Mihan had desirable traits and CrossMV17, Homa, Orum and Cross Azar2 had no desirable germination traits. In non-stress conditions, 11 genotypes had high coleoptile length including Hashtrood, Azar 2, Saein, CD62-6, CD91-12, Mihan, Baran, Heydari, Homa, Cross Azar 2 and Zare genotypes. At 3 bar stress, 11 genotypes had the highest coleoptile length, with the highest values being assigned to Hashtrood, Heidari and Saein. At 6 bar stress, CD91-12 and CD62-6 lines, Hashtrood, Homa, Pishgam, and Zare had the highest coleoptile length. At 3 bar stress cross Azar 2, Saein, CD62-6, Gascogen and HD2985 demonstrated the highest germination rate. Furthermore, Cross Azar2, HD2985, Gascogen, CD62-6 and Saein led to the best results, respectively. However, in both 3 and 6 bar stress conditions Saein, Cross Azar2, CD62-6 and HD2985 were superior for germination stress index (GSI). For grain yield under normal conditions, Gascogen, Heidari, Pishgam, Orum and Zarrineh had the highest yield and Baran, HD2985, C-88-4, C-9011 and Cross Azar2 were placed next. Under stress conditions Baran, Gascogen, HD2985, Cross Azar2, Heidari and Zarrineh consisted the highest performance. According to STI index Gascogen, Heidari, HD2985 and Zarrineh were the most tolerant genotypes to drought stress. Cluster analysis grouped the studied genotypes into 2 clusters, the first cluster comprising 13 genotypes Heidari, Mihan, HD2985, Baran, Pishgam, Hashtrood, Cross Azar 2, CD62-6, Gascogen, Azar 2, Saein, Sadra and Zare. The second cluster consisted of 7 genotypes C-88-4, Zarineh, C-90-11, Orum, CD91-12, CrossMV17 and Homa. Genotypes of cluster 1 were superior in terms of germination traits such as shoot length, coleoptile length, root length and root weight and reduced root/shoot ratio.

Significant differences in all studied traits among genotypes indicated sufficient genetic variation for selection in germination traits. Results showed that Saein, Zare, Pishgam, Sadra, Baran and Mihan cultivars had desirable germination traits and were superior to other genotypes.