IntroductionWHEAT ranks second among cereals in term of global production, but it has been affected by ongoing global climate changes. Drought stress is one of the important factors contributing to the reduction in WHEAT production. Developing drought-tolerant WHEAT varieties currently presents a major challenge for WHEAT breeders. Complex multigenic and multitrait genetic control, high genotype-environment interaction, low heritability, and challenges associated with high-throughput screening of plant traits and genes effective in drought tolerance due to the involvement of numerous traits and positive and negative correlations among them are some of the factors that have made WHEAT variety improvement for drought tolerance a challenging task. Selecting drought-tolerant genotypes as a cost-effective and biologically superior approach to increasing WHEAT production in low humidity areas has always been considered by breeders. Screening WHEAT genotypes to identify drought tolerance sources is essential and can be useful in selecting appropriate and desirable parents for implementing beneficial breeding programs. Local plant populations such as landraces are valuable resources for environmental stress tolerance, including drought stress. Local plant varieties are heterogeneous populations with local adaptation that provide genetic resources capable of meeting the needs imposed by new and emerging agricultural challenges under highly stressful conditions. The aim of this study was to identify WHEAT accessions tolerant to drought stress for use in future breeding programs.Materials and methodsA total of 512 WHEAT accessions from the National Plant Gene Bank of Iran, along with the varieties Kavir, Roshan and Mahouti as controls, were evaluated for drought stress tolerance in the research field of Agricultural and Natural Resources Research Center of Yazd, Iran. The experiment was conducted in two separate augmented designs, one of which was considered to drought stress and the other to normal irrigation conditions. Drought stress was induced by limiting the irrigation cycle. Considering that out of the total studied genetic materials, 141 accessions survived, the evaluation of traits was perfoemed on both those surviving accessions and their corresponding counterparts in the normal experiment. For data analysis, descriptive statistics including minimum, maximum, average, and coefficient of variation were calculated. Correlation coefficients were estimated and tested to study the relationship between traits. Stepwise regression analysis was used to determine the role of each trait and to identify the important and influencing traits on five-spike grain weight. K-means cluster analysis method was used to separate the accessions. All statistical analyzes were performed using R and SPSS softwares.Research findingsThe results of descriptive statistics showed that the highest coefficient of variation under normal and drought stress conditions were attributed to five-spike grain weight (23.35%) and number of fertile tillers per plant (31.67%), respectively. Five-spike grain weight had the highest decrease in range (51.3%) under drought stress compared to normal conditions, and the highest decrease in mean was observed for number of fertile tillers per plant (59.3%) and five-spike grain weight (40.5%), respectively. A large number of accessions showed superiority over control varieties under both normal and drought stress conditions, so that 97 accessions had five-spike grain weight more than the control varieties. The accessions KC12856, KC12776, KC12783, KC12767, and KC12697 with values of 6.77, 6.75, 6.22, 5.94 and 5.86 g, respectively, had the highest five-spike grain weight under drought stress conditions. Number of spikelets per spike, number of florets per spikelet, 100-grain weight and number of grains per spike had significant and strong correlation coefficients at 1% probability level with five-spike grain weight under drought stress conditions. Based on the results of stepwise regression analysis under drought stress conditions, three traits including number of grains per spike, 100-grain weight and spike length were the most effective traits on five-spike grain weight and explained 90.6% of it’s variation. The studied genetic materials were grouped into five separated clusters using K-means cluster analysis.ConclusionThe results of this experiment showed the valuable potential of the studied GERMPLASM to drought stress tolerance. Evaluating the relationships among traits revealed the significance of number of grains per spikelet, number of spikelets per spike, number of florets per spikelet, and 100-grain weight under both normal and drought stress conditions. A considerable number of accessions were superior to the control varieties under both normal and drought stress conditions, indicating the richness and valuable potential of these genetic resources for drought tolerance related traits. Therefore, it is recommended to continue screening and evaluating the WHEAT collection of National Plant Gene Bank of Iran to identify drought stress-tolerant genetic resources. Based on the results of cluster analysis, the control cultivars with different characteristics were grouped in the separate clusters, and a distinguished cluster of the studied WHEAT accessions with superior traits was also formed. The diverse GERMPLASM or superior accessions identified in this study can be used to develope the genetic base in crosses or as parents in breeding programs.

This research was performed with the purpose of screening of WHEAT genotypes and identification of resistance sources to yellow (stripe) rust disease. A total of 284 accessions from BREAD WHEAT collection of National Plant Gene Bank of Iran, which were previously received from 19 countries, were evaluated at adult plat stage under natural incidence of the disease in field condition of Sari, Iran. Based on components of resistance, 116 genotypes were selected for study in the second year at the same condition, among them 52 accessions were then chosen for evaluation at seedling stage in greenhouse. This evaluation was performed by four races 38E158A+, Yr27, 174E10A+, Yr27, 6E2A+, Yr27 and 238E190A+, Yr27. The results showed that 9 genotypes including 8252 and 8320 (Iran), 8395 and 8396 (Korea), 8103 (Afghanistan), 8150 (Portugal), 8348 (Algeria), 8426 (India) and 8472 (Turkey) were resistant to all the studied pathotypes. The presence of Yr1, Yr4, Yr10, and YrSP genes were postulated for these genotypes. One genotype from each country of Portugal, Iran, Japan, Korea, Italy and five genotype with unknown origin were resistant only against pathotype 6E2A+, Yr27, which are likely to carry YrSD or YrND. The comparison of resistance reactions in genotypes 8257, 8237, 8259 and 8332 (Iran), 8105 and 8108 (Afghanistan), 8169 (Portugal), 8458 (India), 8152 (Portugal) and 8362 (Australia) and virulence factors in the studied pathotypes suggested the presence of some unknown resistance genes in regarding genotypes. In the present study some genotypes with adult plant resistance were also identified. The total results of this research indicated the potential of BREAD WHEAT collection of National Plant Gene Bank of Iran to identify new sources and genes for resistance to yellow rust.

Due to WHEAT cultivation in semi-arid regions of the world, much attention is paid to the production these days and introduction of cultivars that do not have a significant yield reduction during drought condition. The healthy and developed roots increase the efficiency of water and nutrients absorption that increase the yield. In this research, root length and number, total length of roots and shoot in embryo stage, root fresh and dry weights, volume, length, shoot length and weight, number of leaves and tillers and also root traits like fineness, diameter, water content, root length, length density, specific mass, texture density, mass density, surface area and density indices in seedling were measured. Descriptive statistics of traits estimated and genotypes were classified into nine groups based on the root depth and texture density. Also, analysis of variance of different groups was estimated. Based on the results, 20 genotypes had dense and deep roots, the best indices for drought tolerance. Most traits, except embryonic stage traits, showed significant differences among genotypes. Discriminant function was performed and the amounts of functions were calculated for each group.

In this research a total of 352 local WHEAT accessions of National Plant Gene-Bank of Iran were evaluated in salt stress condition. The accessions were received from 24 countries and were studied in research field of Ardakan station in Yazd province, Iran with soil EC of 10 ds/m. The seeds of the accessions were planted in an augmented statistical design with three check cultivars of Kavir, Yazd and Mahooti and irrigated by EC=12 ds/m water. Twelve agro morphological traits were recorded according to IPGRI descriptor. The result showed that the highest coefficient of variation (31.27) belonged to number of tillers. Five traits as independent variables including number of seeds per spikes, 100-seed weight, number of florlets per spikelets, number of stem nodes and plant height entered the stepwise regression model and justified 98% of variation in seed weight of five spikes. Based on favorable values of principal components and comparison with check cultivars, 14 accessions were identified as superior. The relationship among the origin of the accessions was investigated by cluster analysis and the countries were located in two groups. The total results of this research indicated the existence of suitable genetic diversity in the studied traits. Besides, BREAD WHEAT GERMPLASM of National Plant Gene Bank of Iran proved to be a rich genetic resource to be exploited for salt tolerance.

Salinity stress is one of the major abiotic stresses in arid and semi-arid regions of the world, such as Iran. High genetic diversity for salinity tolerance has been observed in Iranian BREAD WHEAT genotypes. In order to analyze genetic diversity and determine the most effective characteristics on salinity tolerance, 110 BREAD WHEAT genotypes were evaluated in two conditions (non-stress and saline stress) at the research field of the National Salinity Research Center (NSRC). The salinity of water used in irrigation in stress and non-stress conditions was 10 and 2 ds. m-1, respectively. The results showed that there was a significant genetic variation between studied genotypes. According to cluster analysis based on agronomical and morphological traits, genotypes were divided into 4 categories in both non-stress and stress conditions. According to the results of the means comparison of the groups in non-stress and saline stress conditions, the genotypes No. 2, 5, 7, 8, 9, 10, 11, 12, 13, 31, 35, 38, 73, 81, 97 and 98 were identified as the most salinity-tolerant genotypes. These genotypes can be utilized for salt-affected areas and also as donor parents in WHEAT breeding programs for further improvement of GERMPLASM for salinity tolerance. Also, the results of factor analysis in saline stress condition indicated a positive relationship between biological yield, harvest index and chlorophyll content with seed yield. Generally, it can be concluded that chlorophyll content trait due to the low cost and easy and non-destructive measurement than other traits could be used as a suitable criterion in selecting for increased seed yield in saline stress conditions in field.

Chromosomal arm 1RS of rye (Secale cereale) is one of the most successful foreign resources which was transferred into BREAD WHEAT (Triticum aestivum) and have significant effects on WHEAT breeding. Identifying of two 1AL. 1RS and 1BL. 1RS translocations in WHEAT GERMPLASM had important role in breeding programs. In order to study of distribution of 1RS arm in 956 genotype of BREAD WHEAT three specific primers were used. The O-SEC primer identified 1BL translocation by amplification of 1530 and 710 bp bands in 63 genotypes (6. 68 percent of genotypes) and amplified 900 and 1530 bp bands in two genotypes that can be attributed to the translocation of 1AL. The PAW161 primer was able to amplified 366bp band in 21. 86% and 750bp in 14. 85% of genotypes and the RyeR3/F3 primer amplified 1451 bp band in 11. 29% of the genotypes which indicates the presence of rye arm (1RS) in these genotypes. These primers has amplified several new bands including 1200bp, 1500bp, 800and 400bp in this population. The Agropyron intermedium species has produced 366, 750 and 1200 bp bands by PAW161 primer. Probably this species also carries pieces of 1RS that transmitted into WHEAT. Generally, these three primers divided the studied genotypes into two groups; 686 genotypes not produced any bands and 270 genotypes produced at least one band. Cluster analysis based on molecular data divided 270 genotypes into five groups, at a genetic distance of 15. The range of rescaled distance was from 10 to 25. In general, because of relationship between these markers and various stresses tolerance, the results of this study can be used to improve WHEAT cultivars for resistance to biotic and abiotic stresses and as well as high yield.

Root and crown rot of WHEAT is caused by the fungus Gaeumannomyces graminis var. tritici. "Take-all" is an important disease affecting WHEAT, and its incidence has been reported in several provinces of Iran. To identify resistant cultivars, BREAD WHEAT GERMPLASM should be evaluated. To evaluate BREAD WHEAT GERMPLASM in response to Iranian isolate fungus (T-41) of Gaeumannomyces graminis var. tritici, 333 genotype of BREAD WHEAT, collected from different locations of Iran and other countries were evaluated to take-all in greenhouse conditions. Two experiments were conducted, the first with 89 and the second with 244 genotypes. The measured traits were amount of root and crown infection, disease intensity, wet and dry biomass, and height of shoots. Analysis of variance and means comparison for the parameters indicated that in the first experiment, two genotypes were resistant to the disease, and the rates of disease intensity in these genotypes were 0.13 and 0.06. In the second experiment, five completely resistant genotypes were identified with disease intensity ratings of ' 0'. The identified resistant genotypes screened from both experiments were re-evaluated, and the results were the same. Mean comparison between winter and spring types for dry weight and disease intensity showed that winter WHEAT is more resistant than spring type. The results of this research showed that there is resistance resource to take-all (T-41 isolate), in this GERMPLASM.Since the experiment was conducted in greenhouse conditions, these genotypes should be tested against this disease in infected conditions at field.

To achieve favorable outcomes in breeding programs, selection of parents based on General Combining Ability (GCA) and Specific Combining Ability (SCA) is so important. In order to study the genetic parameters, general and specific combining abilities and the type of disease resistance genes action against take-all disease in BREAD WHEAT, 6 WHEAT genotypes (729, 1622, 2109, 1528, 1546 and 1526) were crossed in one-way diallel cross. Seeds of F1 generations (F1s) and parents were planted in the research greenhouse of Vali-e-Asr University of Rafsanjan, Iran and take-all disease tolerance, stem and root dry weights, tiller number and elements such as manganese (Mn), zink (Zn), potassium (K) and iron (Fe) concentrations in plant tissue were measured. The results of Griffing analysis showed that general and specific combining abilities were significant for all traits except tiller number and K element. In terms of Take-all disease resistance, the best general combiners were 1622 and 729 genotypes, respectively. The best resistant hybrids were 2109×1546, 546×1528 and 1622×1526 that had the highest specific combining ability. Evaluation of genetic parameters by Hayman method for disease index and disease score confirmed the results of Griffing analysis and showed that the dominance and over dominance of gene actions had the greatest importance in genetic control of the resistance to take-all disease (T-41 isolation). Finally, due to low narrow sense heritability and low genetic ratio in resistance to take-all disease, it can be concluded that selection for resistance to take-all disease does not respond well in early generations, so selection after purity, that done by bulk, single-seed descent and double haploid methods can be effective in WHEAT breeding.

The resistance of 72 WHEAT genotypes from collection of National Plant Gene Bank of Iran was assessed to yellow rust in two hot spots of Sari and Karaj, Iran. Both experiments were performed in augmented design and traits of infection type, disease severity, area under disease progress curve (AUDPC) and coefficient of infection were recorded. Based on t-test, two hot spots were significantly different for disease severity (at the first and third evaluations), infection rate (first, second and total), coefficient of infection (first and third) and AUDPC (second and total). Standard deviation of the resistance traits increased by time at both hot spots. Cluster analysis of resistance components grouped AUDPC distinctly at both hot spots. The results of regression analysis indicated strong association of AUDPC with disease severity, infection type and coefficient of infection at both hot spots. Infection rate had higher broad-sense heritability compared to other components of resistance, totally in two hot spots of Karaj and Sari. The results of Mantel test for consistence of distance matrices of accessions based on resistance components at two hot spots along with other results of the research indicated the importance of each components of partial resistance in reaction of the studied accessions to yellow rust. Cluster analysis by resistance components placed the genotypes in two groups of susceptible and partially resistant.

To enhance GERMPLASMs of BREAD WHEAT, a gene, encoding the smallest y-type High Molecular Weight Glutenin Subunit (HMW GS) gene (12.4t) from the D-genome using synthetic hexaploid approach was introgressed into BREAD WHEAT. Tetraploid WHEAT (T. turgidum cv. Langdon) was crossed with T.tauschii accession, AUS24092. Immature embryos were rescued and placed onto Bs regeneration media. Hybrid F1 plants (ABD) were treated with colchicine. Synthetic hexaploid L/24092 was isolated and used in further crossing programs. BREAD WHEAT cvs Baxter and Sunvale were crossed with synthetic hexaploid L/24092. Doubled haploid lines were produced using Fl seeds and phenotyped for the presence of the HMW GS Dy12.4t protein, using SDSPAGE of polymeric proteins. The doubled haploid lines were divided into 17 groups with different combinations of HMW GS, with and without the HMW GS (Dy12.4t) protein for functional studies. This research is a valuable step in evaluation and determination of quality characteristics of WHEAT flour considering storage proteins.