جستجوی مقالات مرتبط با کلیدواژه « terminal drought stress » در نشریات گروه « زراعت »

Hormones play an important role in grain filling regulation (as a reproductive sinks) and the demand for assimilates from current photosynthesis and remobilization sources as well. The objective of this study was to improve sink strength through GA3 application, measuring remobilization and yield under terminal drought stress. Twenty wheat cultivars were cultivated in a split split plot arrangement based on RCBD design with three replications, full irrigation and 40% of field capacity being main plots, GA3 foliar application (60 μM) and control (No GA3) were regarded as sub-plots and wheat cultivars were sub-sub-plots. Grain yield, biological yield, yield components and remobilization (by internodes) were estimated. Significant variation among cultivars was observed under both full irrigation and stress treatments. However, the response of the cultivars to the gibberellin application was almost the same. Drought stress reduced grain yield (33%), biological yield (20%), 1000-seed weight (14%), number of grains per spike (14%) and remobilization (8%), but application of gibberellin increased these traits under both conditions. Gibberellin foliar application at the wheat pollination stage had a positive effect on sink strength and remobilization, especially under full irrigation conditions. Under drought stress conditions, the positive effect of gibberellin application on the studied traits was less due to the reduction of grain filling period. Based on the results of present experiment, foliar application of gibberellin is not recommended under drought stress conditions.

Drought stress is one of the results of climate change that has a negative impact on the growth and yield of crops. Breeding for drought tolerance and production stability are important goals of crop breeding programs in arid and semi-arid regions.

In order to evaluate the stability of grain yield and drought tolerance at barley genotypes in temperate climates of Iran, 20 cultivars and barley lines, in a randomized complete block design with three replications during the two cropping years 2016-2017 and 2017-97 in four stations including Karaj, Varamin, Birjand and Yazd were evaluated under two conditions, normal irrigation and drought stress at the end of the season (irrigation interruption in 50% of heading).

Combined analysis of variance showed that the effects of genotype, year × location, location × genotype and genotype × year × location on grain yield was significant. In order to study the interactions of genotype × environment more precisely and to determine genotypes with stable and drought tolerant yield, different stability parameters and drought tolerance and susceptibility indices were calculated for each genotype. Calculation of stability parameters showed that lines 20, 4, 16 and 15 were recognized as genotypes with stable yield and suitable adaptation, respectively. In terms of drought tolerance indices in the first year, lines 4, 17, 16, 20 and 11 and in the second year, lines 7, 3, 16, 4, 20 and 5, the top genotypes were drought tolerant at the end of the season.

The use of drought tolerance and susceptibility indices, three-dimensional charts and biplot in the first and second years showed that lines 4, 16 and 20 were jointly selected as the best genotypes in terms of drought tolerance in both years, so this the results showed that these lines had good repeatability for drought tolerance. On the other hand, stability statistics also indicated the stability of yield of these lines. so due to grain yield stability, drought tolerance and high yield potential, three lines 4, 16 and 20 were superior and adaptable  lines for normal and terminal drought stress conditions in the temperate climate of Iran that after supplementary  tests can be considered to help production in these areas.

Stem water soluble carbohydrates are one of the major sources of assimilates for seed filling in photosynthesis limitation conditions. The objective of this study was to evaluate the remobilization potential of wheat varieties by potassium iodide. 22 wheat cultivars as sub plots were cultivated in a split plot design with three replications in two growing seasons 2015- 2017 and application and no application of potassium iodide (KI) were main plots. Yield, the number of seed per spike, remobilization, and contribution of remobilization in grain yield were estimated. Significant genotypic variation among cultivars was observed under both normal and KI application. Current photosynthesis elimination decreased the average seed weight per spike by 46%. Grain yield per spike in some cultivars such as Shoosh, Pishgam and Arta and Zare was decresed significantly (up to 65%). The average of grain number per spike was 38 in control, but the application of potassium iodide reduced it to 24% (29 grain per spike). The results of this study showed that the inhibition of current photosynthesis increased the remobilization of assimilate from 3% to 44% in different cultivars. According to the results of cluster analysis, Karim, Shebrang, Hamoon, Pishgam and Dena cultivars had high and also Zare, Chamran and Shush cultivars had low remobilization potentials.

Drought is the most important limiting factor for durum wheat production in the Mediterranean and other regions. Iran is located in arid and semi-arid parts of the word. In order to identify the most effective stress tolerance indices and the most tolerant durum wheat genotypes, this study was conducted as two separate experiments (one under normal irrigation conditions and the other cut off  irrigation after 50% spike) on 20 promising durum wheat lines in a randomized complete block design at three replications. The research was implemented at Neishabour Agricultural Research Station for two cropping seasons. Stress tolerance indices were calculated using the two-year average yield, which were MP, GMP, STI, SSI, TOL, YI, YSI, RDI, DI, MRP and REI. Biplot correlation equations could explain relation between grain yield and calculated indices where GMP, MP and STI were the best ones under both conditions. Lines 7 and 8 were identified as superior genotypes based on GGEBiplot polygon. Keeping in view both yield and stability adopting GGEBiplot, line 7 was favorable. Also Line 7 was ideal genotype in relevant biplot. Generally, results showed that GGEBiplot was suitable methods for identifying superior genotypes based on biplot indices considering both yield and stability.

Wheat, bread and durum, is most important crop of Iran and durum wheat has a historical cultivation background in country. Pasta and macaronis industries of country need 400000 ton of durum annually. To cover this tonnage, releasing and introducing new and high yielding durum cultivar to wheat growers is crucial. On other hand, drought stress, especially terminal drought stress, TDS, is one of the most important factors affecting cultivation of wheat in various environments (Kilic and Yagbasanlar, 2010) and usually happened during filling period in Mediterranean countries (Golabadi et al., 2006). Totally, drought resistance is an erratic and complex trait and its effects depend on growth stage of crop. Lack of drought tolerance cultivars plus drought periods during wheat growing season are main reasons of Iran wheat production fluctuation. Drought resistance indices widely used by scientist to screening and selection drought tolerate wheat genotypes (Bennani et. al., 2017). So to combating these hazard and mitigate effects of water shortage and drought stress on durum wheat production, identifying and releasing new terminal drought tolerate durum wheat cultivars, present study was conducted. The154 durum wheat lines originated from International Maize and Wheat Improvement Center (CIMMYT) plus Syrian4 (Saji) cultivar as durum check were investigated under normal irrigation and TDS conditions at Islamabad Agricultural Research Station over 2013-14 and 2014-15 cropping period. Each plot consisted of 2 rows, 2 m length with 0.3m inter row spaces. Cropping density was 450 seed per m2. Sowing was done by hand. Irrigation cut at boating stage (Z = 4.5) of crop. The grain yield, GY, (Kg/ha) of two years was used to calculating 21 drought tolerance indices namely MP, TOL, SSI, STI, GMP, YI, DI, ATI, SSPI, SNPI, MRP, REI, MSTIk1, MSTIk2, HARM, Red, RDI, GM, DTE. The SPSS software was used for cluster analysis and drawing of bipolot. High variation was observed among the studied lines for GY and drought resistance indices. The cluster analysis by using UPGMA method and square of Euclidean distance, sorted evaluated lines in 6 groups. According to most drought resistance indices and the performance in both environments, the 12 genotypes namely g29, g38, g41, g46, g50, g93, g105, g116, g123, g157, g159 and g199 located at first group and showed remarkable advantages over other groups. The results of the analysis of the main components indicated that g116, g199, g41 and g123 lines were the best genotypes for TDS, which showed good performance under irrigated conditions also. On the other hand, the g50, g46 and g38 lines were the best ones for optimal conditions that showed TDS resistance also. The g29 and g157 lines were among superior lines with less resistance to TDS suitable for optimal conditions, whereas g105, g93 and g159 lines were relatively resistance to TDS with low yield under normal irrigation. Totally four genotypes, g41 (STORLOM/3/RASCON_37/TARRO_2//RASCON_37/4/ D00003A…), g116 (SIMETO/4/DUKEM_1//PATKA_7/YAZI_1/3/PATKA_7/YAZI_1…) g123 (ADAMAR _15/PLATA_18/3/SORA/2*PLATA_12//SOMAT_3/6/LIRO…) and g199 (PLATA_10/6/MQUE/4/ USDA573//QFN/AA_7/3/ALBA-D…), with emphasis on g116 lines, showed potential to mention as candidates to releasing as new cultivars, recommending and presenting to wheat growers of TDS conditions of area of study and similar condition.

Chickpea is one of the most important protein producing crops in the world and drought is the greatest limiting factor for its growth. In addition, chickpea plays crucial role in soil fertility because of the nitrogen fixation in its roots. The chickpea is mostly grown in semi-arid and arid zones or in the rain fed condition. Hence, more than 90% of chickpea growing area is drought prone. Under such conditions, usually the last part of reproductive phase of chickpea, faces water deficiency. Generally terminal drought stress is responsible for reduction in yield and biomass as well as physiological traits such as CO2 assimilation, stomatal conductance, transpiration rate, membrane stability index (MSI) and water use efficiency (WUE). In this condition, stress avoidance ability, tolerance or stress escape is essential for drought resistance. Significant genetic variation exists in chickpea germplasms for terminal drought stress. Nowadays, different breeding methods used for improving chickpea drought tolerance such as Marker assisted selection, omics and mutation breeding. Besides these techniques, enough information about traits affected by drought stress, their genetic parameters and relationships with economic yield is necessary for breeding programs.
 

According to estimation of genetic variation, heritability and relationships between agronomic, morphological and physiological traits, 64 Kabuli type chickpea genotypes were sown under two normal and terminal drought conditions in two-separated 8×8 lattice design in Shahid Bahonar University of Kerman during 2015-2016 growing season. Normal irrigation applied until flowering stage. Water withdrawing was done at 50% of flowering stage. Agronomic traits such as days to secondary branch, days to flowering, days to maturity, plant height, leaflet numbers, seed yield, yield components, harvest index, seed filling period, seed filling rate measured. Chlorophyll content measured by the SPAD chlorophyll meter. Stomatal conductance and net photosynthesis were measured by CI-340 Handheld Photosynthesis System apparatus from Bio-Science Company. Data was analyzed by SPSS ver. 22. Estimation of genetic parameters and path analysis were performed for all significant traits in both normal and terminal drought stress.
 

Analysis of variance for genotypes determined significant differences for day to secondary branch, day to flowering, day to pod setting, 100 seed weight and seed filling period in normal condition. Genotypes showed significant difference for all traits except number of seeds per pod, biological yield, seed filling rate and the SPAD index in stress condition. According to the results of genetic parameter estimation for normal condition the highest amount of CVg was belonged to seed filling period, leaflet number and 100 seed weight, which were 11.1, 9.13 and 8.4, respectively. The highest amount of heritability in normal condition also was belonged to days to flowering and days to secondary branch, which were 68.47 and 68.44, respectively. The highest amount of CVg obtained in terminal drought condition for stomatal conductance and net photosynthesis, were 33.14 and 31.76 respectively. Stomatal limitation and reduction in photosynthesis are the most important factors for loss of yield during stress condition. Therefore, the usage of mentioned genetic diversity may improve future breeding program for drought condition. However, marker assisted selection methods might be helpful, according to moderate heritability of these traits (29.58 and 24.08, respectively). Result of path analysis in normal condition determined that seed-filing period had the most magnitude direct effect (0.527) and the large indirect effect (0.365) via number of seeds per plant on seed yield. The highest amount of direct effect (0.702) on seed yield belonged to rate of filling in drought condition as well. It seems that during terminal progressive drought stress, the ability of filling the seed rapidly is the key trait for tolerant genotypes according to limitation in the seeds filling period.
 

Terminal drought stress is one of two reasonable factors reducing chickpea yield. The result of analysis of variance for genotypes indicated significant differences for days to secondary branch, days to flowering, days to pod setting, 100 seed weight and seed filling period in normal condition. In addition to mentioned traits, significant difference was achieved for days to maturity, seed yield, and number of pods per plant, harvest index, net photosynthesis and stomatal conductance. The highest amount of CVg belonged to seed filling period, leaflet number and 100 seed weight. However, highest CVg belonged to stomatal conductance and net photosynthesis in drought stress condition. In practice, relatively high genetic variation for these traits might be a new insight for improving drought tolerance in chickpea. The high direct and indirect effects of seed filling rate on seed yield in path analysis suggested a strong relationship between these characters. Moreover, the magnitudes of both direct and indirect effect of seed filling rate via number of seed per plant were increased during stress condition. According to the results, some physiological traits such as stomatal conductance, net photosynthesis and seed filling rate might be valuable in future breeding programs.

Barley cultivar Goharan with pedigree of "Rhn-03//L.527/NK1272", was selected among barley genotypes from ICARDA and was identified as is a suitable cultivar for temperate regions under both terminal drought stress and non-stress conditions with different irrigation water management. Preliminary, advanced and elite yield trialsof this cultivar under two conditions (terminal droughtstress and non-stress) were carried out at Karaj, Birjand, Isfahan and Varamin stations. The results of the experiments showed that under non stress conditions, Goharan cultivar had a mean grain yield of 6269 kgha-1 versus 5244 kgha-1 of Rihane ( 20% increase), and under terminal drought stress had mean yield of 4720 kgha-1 versus 4035 kgha-1 of Rihane ( 17% increase). This cultivar, had a mean protein content of 12 percent which indicates its good quality. Study on status of irrigation water use productivity in some drought tolerance barley genotypes showed that cultivar Goharan had the highest amount of water use productivity among genotypes. Results of on-farm trials showed that in average Goharan had 1196 and 623 kgha-1 higher grain yield than Nosrat and Yousef cultivars, respectively under both drought stress and non-stress conditions.Based on importance of water in recent years, drought and lowering of groundwater resources, especially in arid and semi-arid regions of the country,where, there is a competition for irrigation water to cultivate spring products,cultivar Goharan was released for cultivation in non- stress areas and under drought stress in the temperate zone of the country for the sustainability of the barley production.

Terminal drought depending on the geographical area and climatic conditions during the growing season reduces 30 to 60 percent of the chickpea grain yield (Kanouni et al., 2003). By developing new crop management practices and irrigation methods and also using drought stress tolerant varieties, we can compensate the reduction in chickpea yield due to drought stress (Saman et al., 2006). One of the agricultural management is the use of antitranspirate substances such as chitosan (Jan- Mohammadi et al., 2014) and drought stress ameliorators in plants that can tolerate plant stress through physiological activities and intensification of defence mechanisms. The main purpose of this study was to investigate the effects of antitranspirants substances and drought stress ameliorators on grain yield of chickpea under different irrigation regimes. This experiment was conducted in Ekbatan Research Station in Hamedan during the 2014-2015 growing season. A factorial split plot experiment based on CRD design with three replications was used. Four irrigation regimes including non-irrigation, irrigation at flowering stage, irrigation at podding stage and two irrigation flowering + podding stages in main plots and anti- transpiration substances (kaolin 5%, chitosan 200 ml-1) and stress ameliorators (chloride calcium 5 mM, sodium selenate 40 mgL-1) with non spray (control) treatments were placed as factorial in subplots. Seeds were planted with 30 cm row spacings and 31 plants per m2 density at 5 cm depth of soil on March 5th. Weed control was done by hand. Application of stress ameliorators was performed in two stages before and after flowering. Spraying of anti-transpiration substances in the middle of the podding stage was done by hand sprayer on the leaves. In this investigation, the traits related to yield were studied. The results of analysis of variance showed that in addition to the effects of two-way interaction factors, the three-way effects of studied factors on pod length, diameter of grain, and leaf area duration at l% level and the number of pods per plant, number of seeds per plant, grain protein, grain yield, biological yield and water use efficiency traits were significant at 5% level. Twice irrigation regime with chitosan and calcium chloride applications had the highest leaf area duration, and then the once irrigation in podding or flowering stages with chitosan and calcium chloride applications had the maximum leaf area duration. Also, the highest grain diameter, number of pods per plant and number of seeds per plant were obtained in two irrigation regimes with the use of chitosan and calcium chloride. The maximum percentage of grain protein in non-irrigation (dryland) regime was obtained by chitosan and calcium chloride consumption, and then by sodium selenate treatment. The grain protein content of seeds in once irrigation at flowering or podding and two irrigation regimes in flowering + podding stages with spraying chitosan and calcium chloride had 4, 8 and 12 percentage reduction, compared to non-irrigated conditions, respectively. In general, in different irrigation regimes, the spray of chitosan and calcium chloride was more effective than kaolin and sodium selenate on most of the studied traits. The chitosan along with calcium chloride protects the leaf water content and has a positive effect on the development of leaf area which prevents the earlier senescence of the leaves during reproductive stages under drought. Also, their application improves the leaf area duration at the end of the growing season and increases the water use efficiency of the plant. In addition leaf area duration, the highest grain yield and water use efficiency were obtained by irrigation regimes during flowering + podding stages and chitosan spray with calcium chloride. The podding stage irrigation to amount 1910 m3 with chitosan spray and calcium chloride application increased the grain yield by 192% and water use efficiency by 65% compared to the non-irrigation regime. As a result, due to the shortage of atmospheric precipitation during the growing season of chickpea, especially the occurrence of drought at the end of the season, once irrigation regime in the podding stage and spray of chitosan and calcium chloride with mentioned concentrations can be beneficial to increasing the grain yield of chickpea, although in the case of water supply, two irrigation is recommended during flowering and podding stages.

The present study was conducted in the agricultural research farm of Islamic Azad University, Ardabil Branch, to investigate genetic variation of some bread wheat genotypes for some morpho-physiological traits under separate environmental conditions (drought stress and without drought stress). Results from analysis of variance showed that the interaction of “irrigation levels × genotypes” on traits like plant height, infertile tillers number, spike length, peduncle to plant height ratio, spike number per m2 and grain yield were significant. Genotype No. 35 (4057) produced the highest (6.3 ton/ha) grain yield. Linear multivariable regression revealed that traits such as grain numbers per spike, node number and spike weight accounted for about 58% of overall mean yield among the genotypes under terminal drought stress condition. Node number had the highest direct effect (0.438) on grain yield. The results, also, showed that the direct effect of grain number per spike on yield was positive (0.135) while spike weight on yield was negative (-0.345). Direct effect of node number on yield by spike weight was higher than indirect effect of spike weight by node number. Based on the factor analysis, 75.80% of total variations were explained by 6 factors. The first up to the sixth factors accounted for 21.32, 18.13, 9.72, 9.62, 9.4 and 7.6% of the total variations respectively. Furthermore, cluster analysis, based on Ward method and by using Euclidian squared distance, classified the genotypes into five groups. Results from this study suggest that traits such as grain number per spike, node number and spike weight can be used as a selection criteria in breeding programs for higher grain yield of bread wheat in the regions where plants may be subject to terminal drought stress.

Occurrence of drought stress at grain filling period is the prominent and inevitable characteristic of arid and semi-arid regions. The objectives of this research were to determine the effect of water deficiency and the role of current photosynthesis on grain filling, photosynthesis and gas exchange. Therefore, an experiment was carried out in a split-plot design based on a randomized complete block design with three replications at the Research Farm of Razi University in Iran during 2010-2011 cropping season. The irrigation treatments including non water stress (full irrigation over the whole season) and water deficiency stress (irrigation cessation after anthesis stage) were considered as main plots, while the factorial combination of eight wheat cultivars including Bahar, Parsi, Pishtaz, Pishgam, Chamran, Zarin, Sivand, Marvdasht and DN-11 line and the source manipulation treatments including control (Non source limitation), defoliation of flag leaf, defoliation of all leaves except the flag leaf, removing awns and shading over ears, were considered as sub-plots. The results showed that, post-anthesis water deficiency significantly decreased grain yield (22.2%) and 1000-seed weight (18.6%) compared to the control treatment and Removal of photosynthetic sources of assimilates reduced grain yield owing to grain weight reduction. The contribution of spike photosynthesis to grain filling (35.4%) was greater than the flag leaf (18.6%) and lower leaves (18.5%) and also, awns had the lowest contribution to grain filling (3.3%). Grain filling period was shortened during water deficiency stress, so that it reduced from 35 days under control conditions to 28 days under stress conditions, whereas it caused an increase in seed filling rate. Moreover, results indicated that photosynthetic source limitations caused an increase in photosynthetic rate and gas exchange. This increase reflects the compensatory role of photosynthetic rate of remained leaves in preventing yield loss.

To assess the effects of terminal drought stress on phenological traits, grain yield, yield components, and to determine phenotypic variation and relationship between grain yield with other traits in 64 Kabuli genotypes an experiment was carried out using simple lattice design (8×8) under two conditions (terminal drought stress and normal) in 2011 at Research Field of Faculty of Agriculture, University of Tehran, Karaj, Iran. Results showed that there were significant differences among chickpea genotypes which revealed genetic variation for different traits. According to the results of phenotypic correlations, stepwise regression, path analysis for both normal and stress conditions, it can be concluded that, expected that biological yield and harvest index, seed and pod weight, number of filled pods, number of seed.plant-1, 100 seed weight and number of seed.pod 1 were the most important and effective traits affecting yield. Therefore selecting and breeding for these traits could be considered for improving grain yield in Kabuli chickpea. Based on factor analysis using data in both conditions four factors were selected that explained 78.96% and 81.6% of total variation under normal and drought stress conditions. The first and second factors were introduced as yield and yield component factors. Genotype grouping in both conditions was conducted using UPGMA method and the square Euclidean distance. Genotypes were grouped in three clusters in both conditions.

In order to evaluation the effect of terminal drought stress on 5 bread wheat cultivars and for determining their relative tolerance using old (SSI، TOL، MP، GMP، STI، HARM، RDI) and new (SSPI and SNPI) indices, two separate experiments bases on randomized complete block design (RCBD) with 3 replications, were conducted. The results showed positive and significant correlation among stress and non-stress yield (YS and Yp) and indices of SNPI, STI, MP, GMP and HARM. Therefore, the above-mentioned indices are the best and suitable index for relative resistance selection. These results indicated that, Pishgam and Tous were relatively resistant, Sayson was semi-resistant and Alvand and Navid were semi-sensitive cultivars. The results of principal component analysis demonstrated that SNPI and RDI were the best indices and SNPI could select resistant cultivars better than the other ones.

Heritability and gene actions of some important quantitative agronomic traits were studied in the progenies of a cross between a drought tolerant and a susceptible barley lines in normal irrigation and terminal drought stress conditions. A cross was made between two genotypes EC 84-12 and 1-BC-80455 susceptible and tolerant to drought، respectively. Parents as well as F1، F2، BC1 and BC2 generations were evaluated under field conditions in two separate experiments using randomized complete block design (RCBD) with three replications. These experiments were carried out in the research field station، Seed and Plant Improvement Institute، Karaj، Iran in 2005-2006 and 2006-2007 cropping cycles. In normal irrigation and terminal drought stress conditions، irrigation was applied until physiological maturity and anthesis stages، respectively. Plant height، spike length، awn length، grain yield plant-1، 1000 grain weight (TGW)، harvest index (HI)، number of days to heading، number of days to physiological maturity were measured and recorded. Analysis of variances in both environments indicated that significant differences were found between generations for all traits; therefore، generation mean analysis could be performed. Results revealed that under both normal irrigation and terminal drought stress conditions، all traits، except harvest index، were controlled by additive، dominance and epistatic gene effects. For traits as grain yield plant-1، TGW، HI، the contribution of dominance gene effects under terminal drought stress conditions was higher، considering the dominance/additive ratio، as compared to normal irrigation conditions. Comparison of gene actions in both normal irrigation and terminal drought stress conditions indicated that the contribution of dominance genes effects has been increased as compared to the additive gene effect for grain yield plant-1، and harvest index، number of days to physiological maturity، and decreased for plant height، spike length، awn length. In general، for traits showed high ratio of additive to dominance gene effect، selection could be effective in early generation، however for traits with high dominance to additive gene effects selection should be made in later generations till desirable genes are fixed. The broad and narrow sense of heritabilities for the traits under normal irrigation ranged between 0. 43 to 0. 69 and 0. 31 to 0. 43، respectively. In terminal drought stress conditions، heritabities ranged between 0. 41 to 0. 81 and 0. 36 to 0. 45، respectively. The maximum number of genes for the traits under normal irrigation and terminal drought stress conditions was estimated 1. 51 and 4. 32 genes، respectively.

To evaluate terminal drought tolerance in promising lines of spring rapeseed، using stress tolerance indices، this research was conducted in 2008-09 and 2009-2010 growing seasons in Safiabad Agricultural Research Center، Dezfoul، Iran. Eleven promising lines of spring rapeseed as well as Hyola401 (check) were evaluated in two separate field experiments using randomized complete block design with three replications in non-stress and terminal drought stress conditions. Results revealed that L5 and L4 were more tolerant than other lines using Stress Susceptibility Index (SSI) and Tolerance Index (TOL). However، Stress Tolerance Index (STI) and Geometric Mean Productivity identified Hyola401 and L1 line as genotypes with higher yield in both non-stress and drought stress conditions. Considering all drought tolerance indices، Hyola401 and L1 were suitable and adapted genotypes in terminal drought stress conditions. Study of correlation coefficients between seed yield in non-stress and terminal drought stress conditions and STI، GMP and MP showed that these indices are suitable for identification of terminal drought tolerant promising lines of spring rapeseed.

In order to determination the effect of amount, efficiency and contribution of dry matter translated from different aerial organs, on grain yield in advanced wheat genotypes under normal and water stress after anthesis, an experiment carried out at agricultural and natural resources research station of Ardabil in 2008-2009. Eight advanced winter and facultative wheat genotypes compare with Shahriyar and C-80-4 were evaluating in two separated experiment under normal irrigation and after anthesis drought stress condition in a randomized complete block design with three replications. There were observed significantly differences among genotypes in term of remobilization parameters such as amount, efficiency and contribution dry matter on grain yield in both of normal and water stress experiments after anthesis stage. There were observed significantly interaction effects at almost of remobilization parameters between genotypes and water levels. The genotypes with 6 and 10 without different significant have the highest amount of dry matter translated to grain (10.2 and 10.4, respectively) under water stress condition, while there were observed the lowest value of this parameter under drought stress in genotypes with Shahriyar, C-80-4, 3 and 7. Maximum and minimum efficiency in DMT were obtained by genotype 6 in stress condition and genotype 7 under normal condition, also the genotypes with 6 and 10 without different significant had the highest contribution of dry matter translated total, whereas the lowest value of this parameter belonged to 7 genotype which obtained under normal condition. Lowest increasing percent for amount, efficiency and contribution of Dry Matter Translated related to Shahriyar and C-80-4 and highest increasing percent obtained from 4, 5, 6 and 10 Those are satisfactory for cold climates of Iran in terminal drought stress.

To evaluate terminal drought tolerance in barley genotypes and to study the relationship between morpho-physiological traits and grain yield in terminal drought stress conditions, 214 barley genotypes as well as two checks were examined at three locations; Varamin, Birjand and Esfahan Research Field Stations in 2002 -2003 growing season. Morpho-physiological traits including: days to anthesis, days to maturity, plant height, peduncle length, spike length, number of fertile tillers, grain.spike-1 and 1000-grain weight were measure and recorded in three locations. Results indicated significant differences between Six row and two row genotypes for grain yield components (number of fertile tillers, grain.spike-1 and 1000 grain weight), days to heading and spike length. Correlation, stepwise regression and path analyses studies indicated that days to anthesis, peduncle length and 1000 grain weight not only had the highest correlation with grain yield, but also had the highest direct effects on grain yield in both six row and two row barley genotypes. However, these correlations and effects were more pronounced in two row barley genotypes.

To study the response of 180 genotypes of hexaploid wheat to terminal drought stress for grain yield and baking quality properties, a field experiment was conducted at reasearch field station of Seed and Plant Improvement Institute (SPII), Karaj, Iran in 2005-2006 cropping season. Genotypes were planted in two separated experiments simulating non-stress and stress (applied from anthesis to physiologic maturity) conditions using an unreplicated systematic experimental design. Following identification and classification of genotypes in three groups: tolerant genotypes with reasonable yield potential (group A of Fernandez), genotypes with reasonable yield potential and susceptible to drought stress (group B of Fernandez) and moderately tolerant genotypes, genotypes of these three groups were evaluated for baking quality properties. Results of this experiments showed the theory of ''improving bread quality properties of bread wheat under stress conditions'' is only applicable to susceptible genotypes and to some extents to moderately tolerant genotypes, due mainly to increased grain protein content followed by reduction of 1000 grain weight in stress conditions. This theory is not relevant to drought tolerant genotypes, because in these genotypes no considerable change in proportion of protein content to carbohydrates was observed, under stress conditions. The results of this study suggested that identification and selection of genotypess with high grain yield and desirable baking quality properties under non-stress and stress conditions practicable. In this study 7 drought tolerant genotypes with good baking quality were identified in both non-stress and stress conditions. Although susceptible genotypes may gain better baking quality properties under stress conditions, but this is usually compensated by yield penalty.

In order to evaluate rice genotypes for tolerance to terminal drought stress and to identifying tolerant and sensitive genotypes to this stress, 49 rice genotypes were studied in two environments (stressed and non – stressed conditions) using randomized complete blocks design with three replications in Research Field, Faculty of Agricultural Sciences, Guilan University in 2006 cropping season. The studied traits were included: plant height, panicle number plant, grain number panicle, spikelet number panicle, paddy yield, harvest index, relative water content, etc. Analysis of variance showed that there were significant effect (p < 0.01) of genotypes on all traits in two environments, which implies genetic variation among genotypes. Mean comparison of genotypes showed that in two environments, the highest paddy yield belonged to Nemat cultivar (7.31 and 7.07 t/ha respectively), whereas the least paddy yield in non - stressed environment belonged to Dom - sefid,s cultivar (2.74 t/ha) and in drought stressed environment to Diwani,s cultivar (1.46 t/ha). Considering yield components (panicle number/ plant, spikelet number/ panicle, grain number/panicle in Nemat contributed to its higher paddy yield in stressed and non - stressed conditions. Percentage of reduction in traits means by drought stress showed that the paddy yield (40%) was the most affected trait. According to drought resistant indices, the highest mean productivity (MP), geometric mean productivity (GMP), harmonic mean (HM), stress tolerance index (STI), relative water content (RWC) and the least stress susceptibility index (SSI) and tolerance index (TOL) belonged to Nemat,s cultivar. Relationship between drought resistant indices and paddy yield in stressed and non - stressed environments showed that MP, GMP, HM, STI and RWC indices had positive and significant correlation with yield in stress and non - stress environments and would be suitable indices in both environments for selection of drought tolerant cultivars. It is concluded that STI, is the most suitable index among drought indices.

In order to study the response of different winter and facultative wheat (T. aestivum L.) genotypes to terminal drought stress, this experiment was conducted in the Experimental Field of Cereal Research Department, Seed and Plant Improvement Institute at Karaj in 1999/2000 and 2000/2001 cropping seasons. Twenty winter and facultative wheat genotypes were evaluated in two separate experiments, one with non-stress and in the other one, stress was applied from anthesis to physiological maturity. A randomized complete block design with three replications was used. Results of combined analysis of variance of grain yield showed significant difference between genotypes. Genotype x year and genotype x irrigation interactions were significant at 5% probability level, however, genotype x irrigation x year was not significant. Stress tolerance index (STI), stress susceptibility index (SSI), geometric mean productivity (GMP), mean productivity (MP) and tolerance (Tol) were calculated based on the grain yield of the genotypes in both conditions. Among the genotypes number 8 (Pck/Vee) was outstanding. Grain yield of this genotype in non-stressed and stressed conditions was 9320 and 7079 kgha-1, respectively. MP, GMP, STI and SSI for this genotype were 8200 kgha-1, 8123 kgha-1, 0.85 and 0.98, respectively. Results showed that correlation coefficients between STI, GMP and MP indices and grain yield (under both conditions) were positive and highly significant, therefore, these indices can be used to identify high yielding and tolerant genotypes under non-stressed and stressed conditions. Finally, using cluster analysis based on indices and grain yield (in both conditions), genotypes were classified in five groups.