Estimation of drought tolerance among maize landraces from mini-core collection

In order to evaluate drought tolerance of chickpea genotypes and identifying the best indices of drought tolerance, an experiment was conducted at two regions of research field in Mashhad Collage of Agriculture and Agricultural Research Station in Nishabour in 2003 growing season. The 34 genotypes were tested using a randomized complete block design under two irrigated (non stress) and rainfed (stress) conditions. Quantitive drought tolerance and susceptibility indices such as Stress Tolerance Index (STI), Stress Susceptibility Index (SSI), Mean Productivity (MP), Harmonic Mean (HM), Tolerance Index (TOL) and Geometric Mean Productivity (GMP) based on yield in stress and non stress conditions were calculated. Significant differences were found among the genotypes for drought tolerance indices with exception of TOL and SSI . The highest yield was found in genotype numbers of 4,5,16,17,18,19 and 31 respectively genotypes ICCV 93040, ICCV 93042, MCC 13, MCC 448, MCC 5, MCC 10, MCC 16 in non stress conditions but genotype numbers 4,16 and 19 showed merely the highest yield in stress conditions in two regions. Results of regression analysis showed that MP,GMP,STI and HM indices had positive and high significance correlation with yield in stress and non stress conditions . Theses results indicate that MP,GMP,STI and HM are the most suitable criteria for screening drought resistant genotypes. Base on these criteria , genotype numbers of 4,16 and 19 that have the highest yield in stress and non stress conditions and rest near to vectors of drought resistance indices like MP,GMP,STI and HM in multivariate biplot space, Therefore, these genotypes may be recommended as drought tolerant genotypes in this study.

Introduction Drought stress is one of the most important abiotic stresses all around the world. The aim of breeding studies and breeding for resistance to drought is that breeders seek to identify varieties and genetic resources to drought resistant and comparison of drought resistance among the varieties and the introduction of superior varieties to farmers. Drought or imbalance between supply and demand for water is one of the most important limiting factors affecting crop production which is very important in this context, effective and economic use of water resources especially for areas with arid and semi-arid climatic conditions which covers about two-thirds of the total area of Iran (Shahram & Daneshi, 2005). Breeders have been trying that by testing different varieties under normal and stress conditions to identify varieties and use them to plant breeding programs. Cowpea (Vigna unguiculata L. Walp), a member of the family leguminous (Fabaceae) is a crop grown under the tropical and sub-tropical areas covering Africa, Asia, South America, and parts of Southern Europe and United States (Singh et al., 1997). Dry seeds of cowpea contain 20-25% protein, 1.8% fat, and 60.3% carbohydrate and are rich sources of iron and calcium (Majnoon Hoseini, 2008). In this study, various drought tolerance indices were used to identify drought resistant in varieties. Indices included drought tolerance, Tolerance Index (TOL), Mean Productivity (MP), Geometric Mean Productivity (GMP), Stress Susceptibility Index (SSI), Yield Stability Index (YSI), Yield Index (YI), Stress Tolerance Index(STI), and Harmonic Mean (HM) (Ahmadi et al., 2000; Fernandez, 1992; Safari et al., 2007; Bouslama & Schapaugh,1984; Gavuzzi et al.,1997). Materials and Methods In order to study and determine the most effective traits, drought tolerance indices and identify tolerant genotypes in vegetative drought stress on the cowpea genotypes, All 32 cowpea genotypes were cultivated in a randomized complete block design with three replications which each replication consisted of 32 experimental units, each unit or plot, three lines with a length of two meters with line spacing of 70 cm were planted. The distance between rows of plants, 10 cm and 50 cm was considered the distance between each plot, in two separate experiments including normal irrigation and water stress conditions. The study was conducted at Experimental Research Farm, University of Tehran, Karaj Agricultural Research Institute at College of Agriculture and Natural Resources in Karaj, Tehran, Iran during 2014. Drought stress was imposed by doubling the irrigation time about 50 days after planting against normal irrigation on thirty-two cowpea genotypes. Evaluation of drought resistant in different genotypes was conducted using eight indices including Tolerance Index (TOL), Mean Productivity (MP), Geometric Mean Productivity (GMP), Stress Susceptibility Index (SSI), Yield Stability Index (YSI), Yield Index (YI), Stress Tolerance Index (STI), and Harmonic Mean (HM). Results and Discussion Analysis of variance showed that there is a significant difference between genotypes for all the indices of drought tolerance and grain yield in both normal and stress conditions (P0.01). This result suggested that the genetic variation among genotypes is capable of selection for drought tolerance. A simple calculation of statistical parameters (mean and standard deviation) for drought tolerance indices indicated that there is a great diversity among the study genotypes which it can be used as rich genetic resources to help breeders to improve and identify resistant varieties. The average yield of all genotypes under drought stress and normal irrigation condition was Ys = 83.57, and Yp =101.82, respectively. Significant differences between two different conditions indicated that cowpea plant has a high potential for tolerance under drought stress condition. TOL index revealed the lowest average value among various indices (TOL =18.24). The low level of stress tolerance index shows a high relative tolerance genotype. In fact, stress tolerance index showed the changes of stress condition in genotypes. It means that genotypes with low TOL index indicate less changes and genotypes with high TOL index show more changes. Correlation coefficient was calculated to determine the relationship between grain yield and drought tolerance indices. The STI, MP, HM and GMP indices which have the most positive and significant correlation with grain yield under stress and non-stress conditions were introduced as the best indices for screening tolerant genotypes to drought and high-yielding in both environmental conditions. Using Biplot scatter graph in 32 cowpea genotypes and according to genotypes situation in Biplot display, genotypes 998, 313, 291 and 7 were identified as tolerant genotypes with high-yield. Cluster analysis based on investigated indices and yield under drought stress and non-stress conditions showed that genotypes were grouped in four clusters and most of the drought tolerant genotypes with high yield were grouped in the second cluster، while most of drought sensitive genotypes were grouped in the fourth cluster. Conclusions In this study, genotypes showed high genetic diversity in terms of drought tolerance using drought tolerance indices. Based on the results obtained in this study genotypes 291, 7, 313, and the Mashhad cultivar (998) can be proposed as drought tolerant genotypes.

Ten wheat genotypes were tested in a randomized complete block design with three replications under two irrigated and rainfed conditions to identify drought tolerant genotypes. Indices of drought tolerance were calculated based on the potential (Yp) and under stress (Ys) yield. Analysis of variance of indices exhibited highly significant differences among the geometric mean productivity (GMP), mean productivity (MP) and stress tolerance index (STI) and non-significant differences between the stress susceptibility index (SSI) and stress tolerance (TOL) indices. This indicates the existence of genetic variation for the attributes studied and the possibility of selection for drought tolerance genotypes. The highest significant positive correlations were found among GMP, MP and STI indices and potential and under rainfed yield. The highest GMP, MP, and STI were related to the TV2 genotypes. Principal component analysis reduced five indices down to two components with 99.49% proportional cumulative variance. Correlation and principal component analysis indicated that the most suitable criteria for the identification of genotypes under irrigated and rainfed conditions were GMP, MP and STI indices. Three dimensional plots exhibited that TV2 was the best drought tolerance genotype. Results of biplot analysis also identified the same genotype as the highest yielding one in both conditions.

The objective of the present study was genetic analysis of yield-based drought tolerance indices using the diallel method. Twenty-one genotypes of sunflower (Helianthus annuus L.) derived from a half diallel cross between six inbred lines were evaluated in both stress and non-stress conditions using a randomized complete block design for each one. Eight drought tolerance indices comprising stress tolerance index (STI), mean productivity (MP), geometric mean productivity (GMP), harmonic mean (HM), stress susceptibility index (SSI), tolerance index (TOL), yield index (YI) and yield stability index (YSI) were calculated based on grain yield under stress and non-stress environments. Significant genotypic differences were observed in TOL, GMP, MPSTI, HM and YI. Diallel analyses revealed the importance of both additive and non-additive gene effects in GMP, STI, HM and YI. However, the Baker ratio supported the predominance of an additive effect in their expression. Our results demonstrated that SSI, YSI, TOL and MP are not reliable indices to select drought tolerant genotypes in sunflower breeding programmes because of their low heritability. Indices such as GMP, STI, HM and YI were moderately heritable and are usually able to select high-yielding genotypes in both environments and could be usefully employed in drought tolerance breeding programmes of sunflower.

In this study, 40 genotypes of durum wheat (Triticum durum) originating from Iran and Azerbaijan Republic were evaluated in both water-stressed and well-watered environments in 3 years 2008 to 2011 cropping years. In each environment, the genotypes were evaluated using a randomized complete block design with three replications. From the grain yield data, drought tolerance indices comprising of stability tolerance index (STI), mean productivity (MP), geometric mean productivity (GMP), stress susceptibility index (SSI), tolerance index (TOL), yield index (YI) and yield stability index (YSI) were calculated for every genotype. The resulting data were analyzed as obtained from a randomized complete block design. Significant differences among genotypes were observed for all drought tolerance indices. High yield value in non-stress and stress environments was exhibited by genotypes ‘40 (4411.22 kg ha -1) and ‘32’ (4256.34 kg ha -1) respectively. The maximum value of STI (1.07), MP (3642.11) and GMP (3590.85) indices was by genotype ‘35’. The highest value for YI (1.24) was from genotypes ‘39’ and ‘21’. Correlation coefficients revealed that TOL, MP, GMP, STI, HM, and YI indices could effectively be used for screening of drought tolerant genotypes. Using MP, GMP, TOL, YI and STI indices, genotypes UPGMA classification was done and three clusters were established that is paralleled to biplot analysis results. According to results in this study, G10 and G35 were the most drought tolerant genotypes which were clustered as group A. We suggest that tolerance indices including MP, GMP and STI are suitable for durum wheat drought tolerant genotypes selection. Key words: Biplot, Triticum durum Desf., multivariate analysis, water-stressed condition, yield stability.

In this study, 21 genotypes of sunflower ( Helianthus annuus L.) derived from a half diallel cross between six inbred lines were evaluated in both water-stressed and well-watered environments. In each environment, the genotypes were evaluated using a randomized complete block design with three replications. From the grain yield data, drought tolerance indices comprising of stability tolerance index (STI), mean productivity (MP), geometric mean productivity (GMP), harmonic mean (HM), stress susceptibility index (SSI), tolerance index (TOL), yield index (YI) and yield stability index (YSI) were calculated for every genotype. The resulting data were analyzed as obtained from a randomized complete block design. Significant differences among genotypes were observed for all drought tolerance indices except for SSI and YSI. High yield value in non-stress and stress environments was exhibited by genotypes ‘LR4 × LR25’ (14.02 g) and ‘LR25 × C100’ (3.84 g) respectively. The maximum value of STI (0.93), MP (8.72), GMP (6.91) and HM (5.48) indices was by genotype ‘LR4 × LR25’. Correlation coefficients revealed that TOL, MP, GMP, STI, HM, and YI indices could effectively be used for screening of drought tolerant genotypes. Using MP, GMP, HM, TOL, YI and STI indices, genotypes UPGMA classification was done and three clusters were established that paralleled the biplot analysis results. According to results in this study, ‘LR4 × LR25’ is the most drought tolerant genotype which was clustered as group A. We suggest that tolerance indices including MP, GMP and HM are suitable for sunflower drought tolerant genotypes selection.

In order to evaluate and selection of drought tolerant chickpea (Cicer arietinum L.) genotypes and to identify the best indices for drought tolerance, an experiment was conducted at Agricultural Research Station of Neyshabour during 2005-2006 growing season. In this study, 150 Kabuli chickpea genotypes from Mashhad Chickpea Collection of Ferdowsi University of Mashhad, were evaluated in Augmented Design for Preliminary Yield Trials with 6 controls (including drought-sensitive variety, current cultivars and local check). Quantitative drought tolerance and susceptibility indices such as stress tolerance index (STI), stress susceptibility index (SSI), mean productivity (MP), geometric mean productivity (GMP), tolerance index (TOL) and harmonic mean (HM) were estimated based on seed yield in stress and non stress conditions. There were significant differences among genotypes for drought tolerance indices except for TOL and SSI. The highest seed yield in stress condition was found in genotypes MCC302, MCC427, MCC352, MCC1, MCC50, MCC62, MCC118 and MCC423 with 960, 905, 638, 625, 609, 602, 592, and 581 kg/ha, respectively. The highest seed yield in non-stress condition was observed in genotypes MCC312, MCC380, MCC304, MCC50, MCC117, MCC427, MCC301 and MCC311 with 2185, 1856, 1820, 1636, 1622, 1567, 1520 and 1514 kg/ha, respectively. According to the results of regression analysis, MP, STI, GMP and HM indices in chickpea were the best indices for selection drought tolerant genotypes of chickpea. Based on these results, genotype numbers of MCC50, MCC352 and MCC427 are recommended as drought tolerant chickpea genotypes. Key Words: Augmented design, Chickpea, Drought stress, Drought tolerance indices

A study was carried out to evaluate the effect of drought stress on pod yield and other traits of groundnut genotypes to select the ten best performing genotypes using indices. Ninety six genotypes including 90 F2:3 progenies, 4 parents and 2 checks were planted under well-watered (WW) and water-stressed (WS) conditions at the International Crops Research Institute for the Semi-Arid Tropics ICRISAT, Mali. Six selection indices including mean productivity (MP), tolerance (TOL), geometric mean productivity (GMP), stress tolerance index (STI), drought tolerance index (DTI) and reduction (%) (RED) were used. The indices were adjusted based on pod yield under WW and WS conditions. High DTI, STI, MP, and GMP values under both well-watered and water-stressed conditions were more effective in identifying high yielding cultivars under water limited conditions. Based on these indices, the F2:3 progenies ICGV-IS 13012F2-B1-297, ICGV-IS 13012F2-B1-40, ICGV-IS 13005F2-B1-46, ICGV-IS 13005F2-B1-252, ICGV-IS 13012F2-B1-29, ICGV-IS 13005F2-B1-205, ICGV-IS 13005F2-B1-287, ICGV-IS 13012F2-B1-525, ICGV-IS 13012F2-B1-576 and ICGV-IS 13005F2-B1-91 were identified as the most drought tolerant genotypes with high yield stability in the well-watered and drought stress conditions. The indices STI, MP and GMP were positively correlated with pod yield under WW and WS conditions and breeding for drought tolerance. Key words: Groundnut, breeding, selection indices, drought stress.

به‌منظور ارزیابی تحمل به خشکی در ارقام مختلف کلزا براساس شاخص‌های تحمل به خشکی در تنش انتهای فصل رشد، آزمایشی در قالب طرح بلوک‌های کامل تصادفی با سه تکرار در سال زراعی 88-1387 در مزرعه پژوهشی موسسه تحقیقات اصلاح و تهیه نهال و بذر کرج اجرا شد. نتایج بررسی با استفاده از شاخص‌های متفاوت تحمل به خشکی نشان داد که براساس شاخص تحمل به تنش (STI)، میانگین هندسی بهره‌وری (GMP) و بهره‌وری متوسط (MP) ارقام Zarfam، Talaye و GKH 305 به‌عنوان ارقام با عملکرد بالا در هر دو شرایط تنش و بدون تنش و هم‌چنین متحمل به تنش‌خشکی انتهای فصل محسوب شدند. همچنین با توجه به همبستگی مثبت و معنی‌دار شاخص‌های MP، GMP و STI با عملکرد دانه در شرایط مطلوب و تنش، در مجموع این شاخص‌ها به عنوان معیارهای مناسب جهت شناسایی ارقام متحمل به تنش شناخته شدند. نمودار بای‌پلات نیز نشان داد که شاخص‌هایMP، GMP و STI نسبت به یکدیگر دارای بالاترین ضریب همبستگی بودند و ارقام متحمل در مجاورت شاخص‌های تحمل قرار گرفتند. همچنین براساس نتایج به‌دست آمده از نمودارهای پراکنش سه بعدی ارقام Zarfam، GKH 305 و Tassilo به‌عنوان ارقام متحمل به خشکی و ارقام ES Astrid، GK Helena، Modena و Okapi به‌عنوان ارقام حساس شناسایی شدند.

تنش خشکی انتهای فصل از مهم‌ترین عوامل محدودکننده تولید محصولات کشاورزی است. به‌منظور شناسایی ارقام متحمل به خشکی جو از بین 79 رقم خارجی و یک رقم شاهد ایرانی و نیز تعیین ارتباط بین اجزای عملکرد با شاخص‌های تحمل به تنش، آزمایشی تحت شرایط آبیاری نرمال و تنش آبی در مزرعه تحقیقاتی دانشکده کشاورزی دانشگاه شیراز انجام شد. از بین شاخص‌های مختلف تحمل به خشکی،MP، HMP، GMPو STIبیشترین همبستگی مثبت و معنی‌دار را با عملکرد در هردو شرایط آبیاری نرمال و تنش آبی نشان دادند و به‌عنوان بهترین معیارهای تعیین ارقام متحمل تعیین گردیدند. بعلاوه، عملکرد بیولوژیک، تعداد سنبله و وزن صد دانه در هر دو شرایط همبستگی مثبت و معنی‌داری را با شاخص‌های تحمل نشان دادند. با توجه به نتایج تجزیه به مؤلفه‌های اصلی، دو مؤلفه اول توانستند درمجموع 97 درصد از تغییرات را توجیه نمایند که مؤلفه اول به‌عنوان مؤلفه مقاومت و پایداری عملکرد و مؤلفه دوم به‌عنوان مؤلفه حساسیت معرفی شدند. با توجه به آنالیزهای آماری مختلف انجام‌شده ارقام 88 و 145 به‌عنوان متحمل‌ترین ارقام شناسایی شدند. تجزیه خوشه‌ای بر اساس شاخص‌های تحمل تنش و عملکرد در هر دو شرایط تنش و بدون تنش 80 رقم موردبررسی را در چهار گروه مجزا قرارداد. نتایج این تحقیق منبع مناسبی برای استفاده در برنامه‌های اصلاحی ارقام جو پاییزه برای افزایش تنوع ژنتیکی ژرم پلاسم ایرانی و نیز تولید ارقام متحمل به خشکی فراهم می‌آورد.

In order to study the effect of drought stress on eight cultivars corn (Zea mays L.), an experiment was conducted in a factorial experimental on the basis of randomized complete block design under two irrigated conditions during 2010-2011 cropping season. Twelve drought tolerance/resistance indices including stress tolerance index (STI), stress susceptibility index (SSI), tolerance index (TOL), geometric mean production (GMP), mean production (MP), yield index (YI), yield stability index (YSI), drought resistance index (DI), relative drought index (RDI), stress susceptibility percentage index (SSPI) and modified stress tolerance (K1STI and K2STI) were calculated based on grain yield under drought and irrigated conditions. Yield in stress and non-stress conditions were significantly and positively correlated with STI, GMP, MP, YI, TOL, DI, RDI, YSI, SSPI, K1STI, and K2STI and negatively correlated with SSI. Yield in stress and non-stress conditions were significantly and positively correlated with STI, GMP, MP, YI, TOL, DI, RDI, YSI, SSPI, K1STI, and K2STI and negatively correlated with SSI. Screening drought tolerant cultivars using ranking method, three dimensional plots discriminated cultivars ‘KSC720’, KSC 710GT and ‘KSC 700’ as the most drought tolerant. Cluster analysis classified the cultivars into three groups i.e., tolerant, susceptible and semi-susceptible to drought conditions. In general, Results of this study showed that among drought tolerance indices STI, YI, SSPI, K1STI, and K2STI can be used as the most suitable indicators for screening drought tolerant cultivars and ‘KSC720’, KSC 710 GT and ‘KSC 700’ had the highest tolerance to drought in our studies condition.

In order to find the best drought tolerant inbred lines, experiment was performed at the Agricultural College of Islamic Azad University, Shoushtar Branch, Iran during 2010. Experiment treatments were compared in a split-plot design by a randomized complete block design with 3 replications. Main factors included non-stress, drought stress in 6 to 7 leaves (vegetative) stage, drought stress in pollination stage and drought stress in grain filling stage. Sub factors were 7 inbred lines. Five stress tolerance indices, including mean productivity (MP), stress tolerance (TOL), stress susceptibility (SSI), stress tolerance index (STI) and geometric mean productivity (GMP) were used in this study. Drought stress in grain filling stage had the minimum grain yield that showed severe effects of drought stress at this stage of growth. Data analysis revealed that the MP, GMP and STI indices were the more accurate criteria for selection of drought tolerant and high yielding inbred lines. The positive and significant correlation of STI and grain yield under all conditions revealed that this index is more applicable and efficient for selection of parental inbred lines in producing hybrids tolerant to drought in vegetative, pollination and grain filling stages and high yielding under non-stress and stress conditions. Based on the STI, GMP and MP indices, K166B proved to be the most drought tolerant line. Biplot analysis allowed us to distinguish groups of tolerant and sensitive inbred lines. Based on the results of this study, the inbred line K166B can be recommended in future breeding programs for production of drought tolerant hybrids. Key words: Biplot, drought stress, maize, tolerance indices.

In order to study and determine the most effective traits, drought tolerance indices and identify tolerant genotypes in terminal drought stress on the cowpea, an experiment was carried out based on an augment design in two separate conditions in the Karaj Farm, Faculty of Agriculture, Tehran University in 2009. Drought stress was imposed by cutting irrigation after flowering against normal irrigation on 238 cowpea genotypes. Evaluation of studying genotypes under drought conditions was conducted using nine indices, including mean productivity (MP), Harmonic Mean (HARM), Tolerance Index (TOL), Stress Susceptibility index (SSI), Stress Tolerance index (STI), Geometric Mean productivity (GMP), Yield Index (YI), Yield Stability Index (YSI) and Yield Reduction percent (Yr). To determine the relationship between grain yield and indices, Pearson correlation coefficient was calculated. The MP, GMP, HARM and STI indices which have the most significant correlation with yield in stress and non-stress conditions were introduced as the best indices for screening tolerant genotypes to drought and high-yielding in both environmental conditions. Using Biplot scatter graph in 238 cowpea genotypes and according to genotypes status in Biplot scatter graph, 4, 149, 180, 6, 147, 151, 160, 55, 9 and 189 genotypes were identified as tolerant genotypes with high-yield. Cluster analysis based on investigating indices and yield under drought stress and non-stress conditions showed that genotypes was grouped in four clusters and most of drought tolerant genotypes with high yield were grouped in third cluster, while most of sensitive genotypes to drought stress were grouped in the second cluster.

IntroductionDurum wheat (Triticum durum L.) is grown on 10% of the world’s wheat area. In spite of its low acreage, durum wheat is an economically important crop because of its unique characteristics and end products. Drought stress is one of the most devastating environmental stresses that depresses wheat yield productivity in many parts of the world. Breeding for drought tolerance is critical for sustainable wheat production in these areas. Different indices, including tolerance (TOL), mean productivity (MP), geometric mean productivity (GMP), stress tolerance index (STI), stress susceptibility index (SSI), harmonic mean (HAM), yield index (YI), and yield stability index (YSI) have been employed for screening the stress tolerant genotypes. The objectives of the study were to assess durum wheat genotypes under stress and non-stress conditions and to evaluate drought resistance indices in identifying genotypes adapted to the conditions.Materials and methodsThe experiment was carried out at the research farm of Faculty of Agriculture, Razi University, Kermanshah, during 2015-2016 cropping season. In this study, 23 durum wheat genotypes originally from Iran and ICARDA were evaluated using a randomized complete block design with three replications under stress (rain-fed) and non-stress (irrigated) conditions. Irrigated plots were watered three times at flowering and grain filling stages. Rain-fed plots received no water other than rainfall. Grain yield (g/m2) was measured. Tolerance indices were calculated for genotypes based on the grain yield. Combined analysis of variance appropriate to RCBD was carried out using SAS. Environments (rain-fed and irrigated) were considered as fixed effects. Least significant difference (LSD) test was used for the mean comparisons. Orthogonal comparisons and correlation analysis were performed by SAS software. Principal component analysis (PCA) and biplot diagram were carried out by MINITAB 17 and Stat graphics 18.1.01, respectively.Results and discussionThe results of combined analysis of variance showed significant differences between environments (rain-fed and irrigated) and genotypes for grain yield. Orthogonal comparisons showed that there was a significant difference between Iranian genotypes (contrast 1) in both conditions. Also, there were significant differences between ICARDA genotypes (contrast 2) and Iranian and ICARDA genotypes (contrast 3). Results showed that water stress reduced the grain yield of all genotypes and mean grain yield in rain-fed conditions was 32% lower than that in irrigated conditions (the stress intensity was 0.32). Based on all calculated drought indices, in most cases genotypes 15, 10, 18, 12 and 19 were tolerant and genotypes 2, 9, 17, 4 and 7 were susceptible to drought stress. The results of correlation analysis showed that TOL, MP, GMP, STI, YI and HAM had significant (P≤0.01) and positive correlations with grain yield under non-stressed condition. The MP, GMP, STI, YI and HAM revealed a significant (P≤0.01) and positive correlations with yield under stressed condition. Positive and significant correlation were observed between Ys and Yp and also with MP, GMP, STI, YI and HAM indicated that these indices are the most suitable indices to screen genotypes in drought stress conditions. Principal component analysis showed that the first component explained 71% of the variation with Ys, Yp, MP, YI, GMP, STI and HAM. First dimension can be considered as the yield in both environments and drought tolerance. Second component explained 28% of the total obtained variation and can be named drought susceptible dimension. Hence, selection of genotypes with high PCA1 and low PCA2 are suitable for both stress and non-stress environments. Thus, Genotypes 18, 22 and 23 with rather higher PCA1 and lower PCA2 are superior genotypes under both stressed and non-stressed conditions (Group A). Genotypes 19, 14, 3, 16, 21 and 20 could be known as Group B. These genotypes are suitable for non-stressed conditions. Genotypes 4, 7, 17 and 13 are drought susceptible and had low yield in both conditions (Group D). Genotypes 15, 10, 12, 11 and 6 with high amount of yield stability index (YSI) had a relatively low yield in both conditions, but they were more stable genotypes than the others (Group C).ConclusionWhat can be concluded from these results are: 1) Identifying the genotypes with high and stable yield in both conditions which are 18, 22 and 23 originated from ICARDA.2) Identifying genotypes with low yield in both conditions and susceptible to drought which are 4, 7, 17 and 13.3) Suggesting genotypes 19, 14, 3, 16, 21 and 20 for non-stress conditions.

وجود تنش خشکی در ابتدای فصل رشد یکی از مهم‌ترین عوامل تهدیدکننده تولید گندم کشور ‌است. طول کلئوپتل مهم‌ترین صفت مورفولوژیک در تعیین عمق کاشت، قدرت سبز کردن و استقرار گیاهچه‌ است. به منظور ارزیابی تعدادی از ژنوتیپ‌های بومی گندم نان تحت تنش خشکی در مرحله گیاهچه‌ای، آزمایشی با 35 لاین خالص در سه شرایط رطوبتی (شاهد، تنش خشکی با پلی‌اتیلن گلیکول 6 هزار در غلظت‌های 10 و 15 درصد) در قالب طرح کاملا تصادفی با سه تکرار در دانشگاه علوم کشاورزی و منابع طبیعی گرگان انجام شد. اجرا شد. صفت طول کلئوپتیل پس از هشت روز اندازه‌گیری شد. بر اساس مقادیر طول کلئوپتیل در شرایط شاهد (Yp) و شرایط تنش (Ys) شاخص‌های MP، GMP، HM، STI، SSI، YI، TOL، RSI و YSI محاسبه شدند. ضرایب همبستگی شاخص‌های تحمل به خشکی نشان داد که شاخص‌های MP، GMP، HM و STI مناسب‌ترین شاخص‌ها برای انتخاب ژنوتیپ‌های متحمل به خشکی بودند. نتایج تجزیه به مولفه‌های اصلی نشان داد که دو مولفه اول در مجموع 78/99 درصد تغییرات را در شرایط تنش خشکی 10 درصد و 99.80 درصد را در شرایط تنش خشکی 15 درصد توجیه کردند. بر اساس شاخص‌ها و نمودار سه بعدی، ژنوتیپ‌های شماره 3، 6، 11 و 24 (به ترتیب بومی کشور‌های ترکیه، افغانستان، ایران و افغانستان) به عنوان ژنوتیپ‌های متحمل به تنش خشکی در مرحله گیاهچه‌ای شناسایی شدند در حالی که ژنوتیپ‌های شماره 14، 15، 21، 30 و 35 به عنوان حساس‌ترین ژنوتیپ‌ها معرفی شدند. نمودار چند متغیره بای پلات نیز نشان داد که ژنوتیپ‌های متحمل به خشکی در مجاورت بردار‌های مربوط به بهترین شاخص‌های تحمل به خشکی قرار داشتند. از ژنوتیپ‌های بومی شناسایی شده در این پژوهش می‌توان در برنامه‌های اصلاحی گندم نان تحت شرایط تنش خشکی در مرحله گیاهچه‌ای بهره برد.