جستجوی مقالات مرتبط با کلیدواژه "stress tolerance indices" در نشریات گروه "زراعت"

Salinity stress is one of the main abiotic stress factors and environmental problems affecting crop yields worldwide, especially in arid and semi-arid regions. Land salinization is increasing, with 10 million ha of agricultural land destroyed annually. An increase in the concentration of salts in soil solution or irrigation water adversely affects plant growth and productivity, which can substantially reduce yield production. Maize (Zea mays L.) is the third most important cereal grain after rice and wheat, due to its high yield and nutritive value and also known as the queen of cereal crops and is moderately sensitive to salinity stress. Accurate screening of maize tolerant genotypes using selection indices for salinity stress tolerance is an efficient approach to improve salinity tolerant crop plant genotypes, as well as reduce the effect of salinity on this crop.

This study was conducted at the Urmia University Research Farm in 2017 to evaluate the influence of salinity stress (8 dSm-1) on the grain yield of 86 maize lines, as well as identify salt-tolerant maize lines based on selection indices for salinity stress tolerance. The pot experiments in normal and salinity stress conditions were set up in a randomized complete block design (RCBD) with three replicates. Ten selection indices for salinity stress tolerance including Stress Susceptibility Index (SSI), Tolerance Index (TOL), Stress Tolerance Index (STI), Mean Productivity (MP), Geometric Mean Productivity (GMP), Harmonic Mean (HM), Abiotic Tolerance Index (ATI), Drought resistance Index (DI), Modified Stress Tolerance Index in normal condition (MpSTI), and Modified Stress Tolerance Index in stress condition (MsSTI) were calculated based on grain yield of lines under normal and salinity stress conditions.

A wide range of genetic variability was obtained among the studied maize lines in terms of grain yield under normal and salinity stress conditions as well as in terms of selection indices for salinity stress tolerance, which provided suitable conditions for evaluating tolerance indices and selection of tolerant lines. STI, MP, GMP, and HM had the highest correlation with grain yield in both normal and salinity stress conditions and were suitable to screen salt-tolerant and high-yielding maize lines. The three-dimensional (3D) plot obtained from these indices showed that the lines Ma025, Ma010, Ma026, Ma011, Ma009 Ma015, Ma116, Ma012, Ma028, and Ma062, which were in group A, had high yields in both normal and stress conditions. The results obtained from the use of principal component analysis showed that the first two principal components account for 93% of the total variance. The first component, called yield potential, had a very significant correlation with STI, MP, GMP, HM, DI, MpSTI, and MsSTI and was able to separate high-yielding maize lines in both normal and stress conditions. The second component, called sensitive or tolerant to salinity stress, had a very high correlation with SSI, TOL, and ATI and was able to distinguish stable maize lines. According to the hierarchical cluster analysis, a total of 86 maize lines were grouped in three tolerant, semi-tolerant, and sensitive clusters somehow this clustering was completely consistent with the separation of maize lines by the first principal component. In addition, each of these clusters had two subclusters that were separated according to the second principal component, so that in each cluster, the lines that had high yield stability were placed in the first subcluster, and the lines that had lower yield stability were placed in the second subcluster. Thus, Ma010, Ma026, Ma009, Ma027, Ma023, Ma007, and Ma005 were introduced as salt-tolerant maize lines with stable yields to use in breeding programs.

Based on the available findings, the present study, as the first study on a large number of maize lines (86 lines) in the country, evaluated salinity stress tolerance using selection indices. The results of this study revealed the importance of using selection indices for stress tolerance as a reliable and useful tool to improve salinity stress tolerance in maize lines. Accordingly, STI, MP, GMP, and HM were identified as the most appropriate indices for the selection of tolerant and stable maize lines using multivariate statistical methods. It is recommended that the selected maize lines be considered as parent lines in future breeding programs in order to improve salinity stress tolerance and stable grain yield.

IntroductionDurum wheat (Triticum turgidum L. var. durum) or hard wheat, is the second most important wheat crop species. Since durum wheat is mainly cultivated under dryland conditions in the Mediterranean region, its yield is strongly affected by abiotic stresses, especially drought and salinity. Salinity stress causes osmotic stress and disrupts the ionic balance of the cells and plant physiologic processes such as seed germination and seedling growth. This study was conducted to identify durum wheat salinity tolerant genotypes at germination stage using multi-trait selection indices such as multi-trait genotype-ideotype distance index (MGIDI) and the ideal genotype selection index (IGSI). Materials and methodsThe plant materials of this research were 50 different durum wheat genotypes, which were evaluated for salinity tolerance at germination stage. The experiment was conducted as a factorial in a completely randomized design with three replications. To create salinity stress, sodium chloride (NaCl) was used at three levels including 0 (control), 150 mM (~15 dS.m-1), and 300 mM (~30 dS.m-1) concentrations. To evaluate the salinity tolerance of the studied genotypes, quantitative stress tolerance indices were first calculated based on root (radicle) and shoot (plumule) dry weight under non-stress conditions (Yp) and average salinity levels (Ys) for each genotype. Then according to the results of factor analysis based on principal component analysis (PCA), the MGIDI index was calculated using the factor scores of the first two factors with eigen values greater than one. The IGSI index for each genotype was also calculated using all stress tolerance indices. Research findingsThe results of factor analysis based on principal component analysis (PCA) showed that the first two factors with eigen values greater than one explained 99.6 of the total variance. The calculation of the MGIDI index based on the factor scores of the studied genotypes showed that in average salinity stress conditions, genotypes 6, 23, 5, 30, 34, 29, 31, 2, 10, 39, 13, 9, 47, 12, 52, 48, and 1 with lower values of MGIDI (between 0.90 and 2.50) and higher values of IGSI (between 0.65 and 0.80) were the best genotypes in term of salinity tolerance. In contrast, genotypes 46, 43, 19, 26, 4, 15, 42, 38,11, and 37 with the lower values of IGSI and the higher values of MGIDI, were considered as weak and sensitive genotypes to salinity. The coefficient of determination (R2) between these two indices for all genotypes was 92%, indicating a high correlation between these two indices and the selection of same genotypes. ConclusionThe results of the present study showed that there was a significant genetic diversity among the studied durum wheat genotypes for salinity tolerance at the germination stage, which can be used in the breeding programs of this valuable crop. IGSI and MGIDI indices were also effective in identifying superior genotypes based on all stress tolerance indices. Therefore, these indices can be recommended to select salinity tolerant genotypes based on different traits in breeding programs.

Rapeseed is a main oilseed crop in the world. Water deficiency is the main cause of reduced crop yield under drought stress. The highest rapeseed yield reduce was resulted when water deficit occurred at flowering and pod developmental stages (Kahrizi and Allahvarand, 2012). Knowing about the traits that affect grain yield, so that by improving these traits, grain yield can be increased, plays an important role for being successful breeding programs. Factor analysis of multivariate statistical methods is for a deeper understanding of the relationships between traits and is an effective statistical method in reducing data volume (Cooper, 1983). The aim of this study was to study the effect of late-season drought stress on some traits affecting the yield of studied rapeseed genotypes and to identify genotypes compatible with normal and drought stress conditions using some stress tolerance indices.

This experiment was carried out at the research field of Seed and Plant Improvement Institute, Karaj, Iran, on 2016-2018 growing seasons under full irrigation conditions and late-season drought stress (from beginning pod setting stage) on new winter rapeseed genotypes in a randomized complete block design with three replications. Some of morphological, physiological, phenological traits, yield and yield components were measured. Factor analysis was performed to determine the most influential variables. To identify drought tolerance genotypes, drought tolerance indices such as tolerance index (TOL), stress susceptibility index (SSI), mean productivity (MP), geometric mean productivity (GMP), harmonic mean (HMP), stress tolerance index (STI), Yield index (YI), Sensitivity drought index (SDI) and yield stability index (YSI) were used.

The combined analysis of variance showed that the effect of drought stress on all evaluation traits was significant except for height of the first branch, days to end of flowering, flowering period and oil percentage. The results showed that drought stress decreased Grain yeald, Pods per plant, Seeds per pod, 1000 Seed weight, plant height, Chlorophyll a and b, Cartenoid, Relative water content and Days to maturity; while it increased Chlorophyll Index (SPAD).The results of factor analysis exhibited three factors in normal and drought stress conditions, which explained 79.7% and 82.51% of the variation, respectively. This factors in normal conditions were named "Yield", "Plant pigment", "Phenological traits" respectively, and in stress conditions were named " productivity", "Plant pigment" and " sink" , respectively. It seems that its seams possible to use these traits as selection criteria in breeding programs for improve grain yield of winter rapeseed genotypes results showed that GMP, MP, HMP and STI indices were positively correlated with grain yield under both stress and non-stress conditions. Therefore, they can be exploited not only to screen drought tolerance but also to identify superior genotypes for both stress and non-stress field conditions (Fernandez, 1992). Principal component analysis using grain yield under both conditions and drought tolerance indices showed that the genotypes Nafis, Vesuvio, Medea, HL3721 and HL2012 were the most tolerant genotypes to drought conditions, while the genotypes Extorm, Excalibur, Danube and Expower were the most sensitive genotypes. With cluster analysis using WARD procedure based on drought tolerance, the studied genotypes were grouped in 3 separate clusters. The first group consisted of genotypes that have high yield and drought tolerant and had appropriate and reliable values of indices such as STI, MP, GMP, HMP. Therefore, this group (genotypes Nafis, Vesuvio, Medea, HL3721 and HL2012) are drought tolerant group. The second group had genotypes with low values of STI, MP, GMP, HMP as well as Ys and Yp and higher values of SSI. Therefore, genotypes Danube, Excalibur, Expower, Harnus and Extorm with low yield and drought sensitivity were placed in this cluster. The next group (Okapi, Ahmadi, Nima, Natalie, SLM046, Artist) with average yield in both non-stress and stress conditions, and less sensitivity to drought stress condition, were stable in yield, and therefore considered as semi-resistant cultivars.

The cow cockle (Vaccaria hispanica (Mill.) Rauschert) is an annual plant of the Caryophyllaceae family with a chromosome number of (2n=2x=30). This plant grows upright to a height of 30 to 100 cm with several branches and has great potential for producing medicinal products due to its triterpenoid saponins. In arid and semi-arid regions, plants experience periods of lack of moisture during their growth period and must be able to tolerate these periods to produce a proper yield. This experiment was aimed at investigating the drought stress responses of different V. hispanica ecotypes and evaluating their drought stress tolerance.

This experiment was performed as a split-plot experiment based on a randomized complete block design with three replications in 2020-2021 at Parsabad Agricultural Station. The main plots were allocated to three treatments of non-stress, moderate and severe stress (irrigation cycles of 7, 10, and 14 days, respectively), and sub-plots were assigned to eight native cow cockle ecotypes collected from different northwestern regions of Iran. Seeds were sown directly in the soil at a rate of 5.5 to 8 kg per hectare with a depth of 1-2 cm, and a row spacing of 20 cm. Irrigation operations were performed similarly for all experimental units up to the beginning of stem elongation, after which the irrigation intervals for applying stress were increased. At maturity, seed yield, biomass, and harvest index were recorded and various tolerance and sensitivity indices were calculated using the yield of each ecotype under non-stress conditions (Yp) and stress conditions (Ys).

The results of the analysis of variance showed that the effects of irrigation regime, ecotype and their interaction were significant in terms of seed yield, biological yield and harvest index. Ecotype 6 had the lowest decrease in grain yield per unit area and harvest index under stress conditions. In terms of yield stability and drought tolerance indices, harmonic mean yield, geometric mean yield and mean productivity, the lowest values in moderate and severe stress conditions were related to ecotypes 7 and 1, respectively, and the highest values of these indices were related to ecotype 6 in both stress conditions. Estimation of SIIG index for different ecotypes showed that ecotype 6 had the highest amount of the SIIG in both moderate and severe stress conditions. Ecotypes 4 and 3 in moderate and severe stress conditions were in the next rank and were classified as ecotypes with relatively high drought tolerance. In moderate stress conditions, ecotypes 7 and 8 and in severe stress conditions, ecotypes 1 and 7 with the lowest SIIG showed high sensitivity to drought stress. Factor analysis based on principal component analysis (PCA) showed that the first two factors with specific values greater than one, in both moderate and severe stress conditions had 95.58% and 97.18% of the total variance, respectively. According to the MGIDI index, in moderate stress conditions, ecotype 6 had the lowest value and was considered the most tolerant ecotype to drought stress, followed by ecotypes 4 and 3. In severe stress conditions, after ecotype 6, ecotypes 3 and 4 were in the next rank.

Estimation of the ideal genotype selection index (SIIG) and the multi-trait genotype–ideotype distance index (MGIDI) for different ecotypes based on all tolerance indices showed that ecotype 6 had the highest SIIG and the lowest MGIDI in both stress conditions followed by ecotypes 4 and 3. Ecotypes 1, 7, and 8 with the lowest SIIG and the highest MGIDI showed high sensitivity to drought stress. Therefore, among the studied ecotypes, ecotype 6 can be considered as the most tolerant ecotype to drought stress. At all, it can be concluded that the studied ecotypes have sufficient genetic diversity to be used in breeding programs with the aim of obtaining lines with higher tolerance to drought stress. The use of SIIG and MGIDI indices in crop selection programs can also be considered more.

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.

Today, wheat is grown on more land area than any other commercial crop and continues to be the most important food grain source for humans. Its production leads all crops, including rice, maize and potatoes. Wheat is the most widely grown crop in the world and provides 20% of the daily protein and of the food calories for 4.5 billion people. It is the second most important food crop in the developing world after rice. Drought is a major environmental stress threatening wheat productivity worldwide. Global climate models predict changed precipitation patterns with frequent episodes of drought. Although drought impedes wheat performance at all growth stages, it is more critical during the flowering and grain-filling(terminal drought) and results in substantial yield losses. So drought stress is one of the most common environmental stresses that makes production limitation in wheat. According to the FAO, 90 percent of Iran is located in dry and semi-arid areas. Iran, with an average rainfall of about 250 mm, has an average of about one-third of the world's rainfall. At present, the population of Iran is about 80 million and according to forecasts, the Iranian population will pass 120 million by 2020, based on a growth rate of 2% in 1400. Therefore, increased wheat production is inevitable. In order to identify drought stress tolerant wheat genotypes in greenhouse and field, 30 genotypes were studied as a sub factor in split plot experiment in a completely randomized design with randomized complete block design with three replications under normal and drought stress conditions in 2016-17. and discussion Analysis of variance showed a significant difference between genotypes in terms of grain yield under stress and non-stress conditions. In terms of seed yield in the field, genotypes cd-1, c-93-10 and Mihan with mean of 290.535, 282.835, 311.229 g/m2 were the most tolerant and in the greenhouse, Urom and C-93-8 genotypes with an average of 5.769 and 5.236 g in 5 plants per plant were identified as the most susceptible genotype for drought stress. Also, based on the genotypic groupings based on the stress tolerance indices in field and greenhouse experiments, genotypes were located in four clusters and genotypes of cd-7, c-94-4, cd-2, c-93-5, c-93-9, cd-10, cd-11, cd-5, c- 94-6, c-94-8, cd-9, c-94-7, cd-1, c-93-3, c-93-10, and Urom were known as the most susceptible which were suitable for crosses or introductions for farmers in the target area. Considering that the use of an index is not effective for introducing the most tolerant figure and based on this principle, the results of genotypic grouping based on all indices, showed that the genotype was considered as the most tolerant genotype under greenhouse conditions due to low TOL, SSI and YP, YS, MP, GMP, HMP, STI, YI and YSI. Also, under field conditions, genotypes cd-7, c-94-4, cd-2, c-93-5, c-93-9, cd-10, cd-11, cd-5, c-94-6, c-94-8, cd-9, c-94-7, cd-1, c-93-3 and c-93-10, according to most indices, are most susceptible under field conditions. And are applicable in breeding programs for the production of high tolerance cultivars to end-of-season stress.

To evaluate the effect of deficit irrigation and within row spacing on grain yield and yield components of grain sorghum promising lines, an experiment was conducted as split plot-factorial arrangement in randomized complete block design with three replications in 2015 and 2016 at the research field of Seed and Plant Improvement Institute, Karaj, Iran. Main plots consisted of three irrigation regimes (irrigation applied after 60, 120 and 180 mm cumulative evaporation from Class A pan) and sub-plots included factorial combination of three levels of within row spacing [8, 12 and 15 cm (21, 14 and 11 plant.m-2, respectively)] and three promising lines of grain sorghum (KGS23, KGS32, and KGS36). Combined analysis of variance showed that the sorghum prmising lines differed significantly for grain yield. The highest (5333 kg.ha-1) and lowest (4011 kg.ha-1) grain yield obtained from promising lines KGS23 and KGS32, respectively. The results showed that the response of the grain sorghum promising lines to the irrigation regimes was different, and KGS23 was significantly superior in comparison with the other two lines for most of the studied traits. In addition to high grain yield and desirable morphological traits, KGS23 showed adaptibility to deficit irrigation conditions. KGS36 ranked next to KGS23 for grain yield and tolerance to deficit irrigation. The effect of within row spacing on forage yield and biological yield was significant. Decreasing the within row spacing increased the forage and biological yields. Considering the stress tolerance (STI), geometric mean productivity (GMP) and grain yiled, KGS23 promising line which had higher grain yield in all irrigation regimes was identified as tolerant line with high grain yield.

In order to study the response of 120 genotypes of rapeseed (including 100 hybrids and 20 parents) in terms of cold stress tolerance, an experiment was conducted in α-lattice design with two replications under normal (September) and late sowing (October) conditions during two years. Combined analysis of variance showed that genotypes were significantly different at 1% and there was a significant genetic variation among the studied genotypes. In addition, there was a significant difference between the environments (normal and late sowing) at 1% in both years and the effect of late sowing on the yield of rapeseed was different from that of normal sowing. Total mean of seed yield in non-stressed condition was 4.9 ton/ha and in cold stress condition was 2.72 t/ha (34% reduction compared to normal sowing conditions). Principal component analysis (PCA) using six indices of cold stress tolerance (MP, GMP, HARM, TOL, SSI and STI) showed that the first two components justify about 99.85% of the variation in the population. The biplot of first and second components divided the genotypes into four different groups and identified 29 high yielding and cold tolerant genotypes. Similarly, cluster analysis divided the genotypes into four different groups and grouping of genotypes using cluster analysis showed good agreement with the results of principal component analysis. Correlation between different indices of stress tolerance and yield in stress (YP) and non- stress (YS) condition showed that TOL and SSI had positive correlation with YP and negative correlation with YS. Furthermore, the four indices of MP, GMP, HARM and STI showed positive and significant correlation with yield in both stressed and non-stress conditions. The results of this study showed that the STI index has a high efficiency in selection of rapeseed genotypes for cold tolerance and can be successfully applied in breeding programs.

Although the non-Iranian primary tritipyrum lines (NIPTLs) have been produce and have shown potential to be a new slat tolerant cereal, however, have a few undesirable traits such as brittle rachis, keep in tiller production and late maturity. In order to remove these traits, the crossing of NIPTLs with Iranian bread wheat cultivars led to new recombinant Iranian secondary tritipyrum lines. In this study the 13 non-Iranian primary tritipyrum lines (NIPTLs: 2n = 6x = 42; AABBEbEb) and Iranian secondary tritipyrum lines (ISTL: F6-F7; 2n=6x=42, AABBD(1-6)"Eb(1-6)"), 6 Iranian bread wheat cultivars and 1 promising triticale line were evaluated at two research centers using an alpha lattice design with two replications under normal (1 dS m-1) and salinity stress ( 12dS m-1) conditions during growing seasons of 2014-2016 at Kerman province of Iran. The results indicated grain yield was strongly affected by salinity with reduction ratio of 11.06, 9.37, 4.30, 4.98, 7.98, 12.58, in Iranian chromosomally recombinant secondary individuals tritipyrum plants obtained from crosses such as (Cathlicum × Ma/b), (Falat× Ma/b), {Omid × (Ka/b)(Cr/b)}, {Niknejad × (Ka/b)(Cr/b)}, (Shotordandan × ka/b), (Roushan × Az/b), respectively, in comparison with Non Iranian Primay Ttritipyrum Lines (NIPRLs) (3.48), Iranian bread wheat cultivars (19.90) and promising triticale line (15.87) The evaluation of stress tolerance indices showed that STI could effectively be used for screening of salinity tolerant genotypes because it had the highest correlation coefficients with grain yield. The (Cr/b) × (Ka/b) line of NIPTLs and the lines obtained from Niknejad × (Ka/b)(Cr/b) and Omid × (Ka/b)(Cr/b) crosses showed the highest average breeding value which will be suitable for breeding programs of ISTLs lines with high yield potential in saline soils and brachish waters.

This study was carried out in laboratory and field in Maragheh Dryland Agricultural Research Station. The field experiment was in split-split plots based on randomized complete block design (RCBD) with three replications performed for three cropping seasons (2010-2013). Drought stress levels as main plots were one time irrigation (immediately after planting), two times (after planting flowering) and three times (after planting flowering time pods filling), four chickpea genotypes (Arman, Azad, ILC 482 and a landrace from Turkey) were in sub plots and three seed sizes (large with > 8 mm, medium with 6-8 mm and small with

To evaluate and compare different rice genotypes under salinity conditions, two separate experiments under two salinity and non-salinity fields were conducted in randomized complete block design with three replications in west of Guilan province (Astara) during 2009-2010. Results of the analysis of variance showed that there were significant differences between the salinity conditions, varieties and variety × stress interaction effect for grain yield at the 1% probability level. Mean comparison of the total grain yield indicated that the varieties Gharib-Siahreihani and Hashemi had the highest and IR29 the lowest grain yield. Mean comparison of variety × salinity interaction effect showed that the highest grain yield under non-salinity condition belonged to Gharib-Siahreihani and Hasansaraei-Atashgah while under salinity condition, Hashemi produced higher grain yield. In contrast, the lower grain yield under both stress and non-stress conditions belonged to IR29 variety. Hashemi variety had the higher stress tolerance index than the other varieties. Principal component analysis based on grain yield and stress tolerance and susceptibility indices identified two principal components with eigen values greater than one explaining 99.9 % of the total variance in the studied population. Distribution of the studied cultivars based on biplot of the grain yield and these indices presented Hashemi, Tarom-Amiri, Tarom-Pakotah and Garib-Siahreihani as tolerant varieties and IR29 as sensitive variety to salinity stress. Tolerant varieties are recommended to improve salinity tolerance in the rice breeding programs.

In order to evaluate drought tolerance of some Aegilops triuncialis ecotypes a factorial experiment based on a completely randomized design was conducted under non-stress and drought stress (irrigation until 50% of heading) condition in the greenhouse of Mohaghegh Ardabili University in 2012. Drought tolerance and susceptibility indices for grain yield were calculated and principal component analysis was performed based on these indices. The results showed that based on the stress susceptibility index (SSI) and stress tolerance index (TOL) Horand and Karaj ecotypes are less sensitive to water stress. In terms of stress tolerance index (STI) and geometric mean productivity index (GMP) which a high values of them indicates tolerance of studied ecotypes، Hashtrood ecotype were identified as a tolerant ecotype. Grouping of ecotypes in a three dimensional graph based on the yield the in non-stress (Yp)، yield the in stress condition (Ys) and stress tolerance index (STI)، showed that Maku and Hashtrood ecotypes under both non-stress and drought stress conditions، and Horand ecotype under stress condition have higher performance. With Principal components analysis and biplot diagram، Hashtrood، Maku and Horand ecotypes were identified as drought tolerant. According to significant correlation between STI، GMP، MSTI1 and MSTI2 indices with yield under stress and non-stress conditions، these indices can be used for determination of tolerant ecotypes.

In order to study of drought stress on physiological and agronomical characteristics of rapeseed varieties، an experiment was carried out as split plot based on randomized complete block design with three replications at Yazd region during of 2011-2012. Irrigation treatments was designed in two levels as main plot including irrigation after 80 mm evaporation from evaporation pan، class A (control treatment) and drought stress as withholding irrigation from flowering stage، and varieties lilian، Cooper and Savannah as sub plots. Sampling stages was done 7، 12 and 26 days after treatment. The results indicated that drought stress significantly decreased the stomatal conductivity، relative water content (RWC)، plant height، silique per plant، 1000 grain weight and grain yield، whereas، in comparison with control SPAD value was higher. Lilian indicated the higher stomatal conductivity (196 mmol m-2 s-1) and RWC، silique per plant (300 silique)، 1000 grain weight (4. 06 g) and grain yield (1411 kg. ha-1). In this study، Geometric mean productivity (GMP) and Stress tolerance index (STI) had the high correlation with grain yield in normal and drought stress conditions. Also، Bi-plot diagram based on two principal components indicated that Lilian variety with higher GMP and STI indices in addition with higher GMP and STI both in stress and non stress environment had the highest grain yield.

A field study was carried out in 2007 to determine the response of promising genotypes of Mung bean to late season drought stress at zabol climatic condition. The experiment was conducted in a randomized complete block design with three replications at two locations (with and without drought stress). Treatments were 6 different genotypes of Mung bean. All treatments in two fields were irrigated normally until 50% heading stage. The last irrigation in drought stress conditions was done at 50% heading stage and then plants were developed under stress conditions until harvesting. Comparisons of traits in both conditions showed that water stress have negatively affected plant growth. The stress conditions had the highest effects on yield and the least effects on number of slinked pod. For evaluation of drought stress tolerance indices such as mean productivity (MP)، geometric mean productivity (GMP)، stress tolerance index (STI)، tolerance index (TOL)، stress sensitivity index (SSI)، harmonic mean of productivity (HARM)، were used. According to these indices، genotype PUSA was the most tolerant and the genotypes MN22 and MN92 were the most sensitive genotypes to drought stress. Principal component analysis used to study the relationship between indices. Two first components could explain more than 99% of variations of indices. Also، biplot of PC1 and PC2 showed the genotype PUSA was the most tolerant and the genotypes MN22 and MN92 were the most sensitive genotypes to last season drought stress between evaluated genotypes of Mung bean in zabol climatic conditions.

In order to evaluate terminal drought tolerance in different Canola cultivars based on drought tolerance indices, an experiment was conducted based on randomized complete block design (RCBD) with three replications at experimental field of Seed and Plant Improvement Institute (SPII), Karaj in 2008-09. Results using stress tolerance index (STI), geometric mean productivity (GMP) and mean productivity (MP) indices revealed Zarfam, Talaye and GKH305, were as cultivars with highest yield in both optimum irrigation and terminal drought conditions. High and positive correlation between STI, GMP and MP indices with yield in optimum and drought conditions indicated that they were as the best indices for introduction and characterization of drought tolerant canola cultivars. Biplot graph showed that MP, GMP and STI indices had high correlation coefficient with each other, and tolerant genotypes were located near tolerance indices. Also results of three dimensional scatter plot indicated that cultivars Zarfam, GKH 305 and Tassilo were recognized as tolerant genotypes to drought stress, and cultivars ES Astrid, GK Helena, Modena and Okapi were identified as sensitive genotypes.

The effect of late planting heat stress on yield and yield components was studied in 11 barley lines from ICARDA and one cultivar from Iran (Izeh) during two years (2005-2007) in Gachsaran Dry-land Agricultural Research Station. Each line was planted in a 6-rowed plot at two dates: normal planting (middle of November) and late planting (end of December) with three replications using a randomized complete block design. Results showed that heat stress (late planting) significantly decreased the number of spikes per unit area, grains per spike, thousand-grain weight and grain yield by 25.2%, 6.3%, 3.6% and 34.8%, respectively, while grain filling period did not show a significant reduction under heat stress. The number of days to heading showed the highest correlation with yield (-0.65). Mean product (MP), geometric mean productivity (GMP) and stress tolerance index (STI) were the best tolerance indices showing the highest correlation with grain yield under both normal and heat stress conditions. Based on two years data of STI, GMP, MP and yield, line 6 turned to be the most tolerant line and could be recommended for cultivation in tropical areas of Iran.

In order to compare the efficiency of multivariate statistical methods (cluster analysis and Principal Component Analysis: PCA) with a new method known as "2- step screening method" for selection of wheat genotypes with high yield potential and good drought tolerance, this study was performed. For this, 180 hexaploid wheat genotypes were studied during 2005/2006 cropping season under two conditions of well irrigation and shortage of water (from anthesis on wards) in Karaj. Drought resistance indices including stress susceptibility index (SSI), tolerance index (TOL), mean productivity (MP), stress tolerance index (STI) and geometric mean productivity (GMP) were calculated for all investigated genotypes. Study of correlation coefficients among these indices and grain yield in two conditions for all genotypes showed that STI is better than other indices for screening genotypes with favorable yield in both conditions. But, because the STI value was still significantly affected by higher grain yield in normal conditions, identifying favorable genotypes followed using 3 methods. Study of grain yield under normal and stress conditions and tolerance indices showed that "2-step screening method" is more efficient than the other two methods. This method is based on completing cluster analysis with application of a defined cut off line for SSI index (through establishing a relationship between SI and SSI) to screen out stress susceptible genotypes among first step selected genotypes, hence suggested to be applied in breeding programs.

Sugarcane (Saccharum officinarum L.) is one of the most important sugar crops that provides the major part of consumed sugar of the people worldwide. Because of the excessive demand for sugar and its byproducts, cultivation of sugarcane is expanding rapidly in subtropical arid and semi-arid regions such as south-west of Iran. Salinity is an important abiotic stress that causes reduction in sugarcane yield under saline and sodic conditions of soil and water in Khuzestan province. This study was conducted to evaluate seven commercial and promising sugarcane cultivars at formative stage for different stress tolerance indices and distribution of genotypes and indices in 3-D plots and biplots by using a complete randomized design with three replicates and four salinity treatments (0, 0.25, 0.5, 0.75 % NaCl) in a hydroponics system at research greenhouse of Isfahan University of Technology (IUT). Different tolerance and sensitivity indices for dry weight yield of sugarcane cultivars showed that NCO-310 genotype had high dry matter yielding potential in all stress levels. Also CP82-1592 genotype in medium and high level stress intensities had potential to yield relatively high dry matter and low sensitivity to salinity stress. Based on stress tolerance index (STI) revealed that NCO-310 (a commercial cultivar) and CP82-1592 (a promising line) at all salinity levels were the most tolerant cultivars.

To determine the genotypes with high yield and tolerance to drought stress and find the best drought stress indices, a field experiment was carried out in a randomized complete block design with three replications. In this experiment six genotypes of sunflower Azargol, Allstar, Record, Mehr, CMS60/52*R82 and CMS19*R256 were evaluated at Islamabad Research Station in 2002-2003. Genotypes were planted in two separate experiments, one with normal irrigation and the other with three irrigations in planting, buding and flowering stages. Results showed that drought stress caused a severe reduction in leaf area index, grain and oil yield, stem diameter and plant height. Under normal irrigation condition the highest grain yield obtained from Mehr and Record with 3908 and 3901 kgha-1, respectively. In drought stress conditions, the highest grain yield obtained from Azargol and Record with 2850 and 2634 kgha-1, respectively. It appeared that stress tolerance index (STI) and geometrical mean (GMP) might be the best indices to evaluate the genotypes for drought stress tolerance