Study of seed germination indices in bread wheat genotypes (Tritium aestivum L.) under drought stress simulated with polyethylene glycol

Introduction Wheat is a major crop among cereals and plays a critical role in the national economy of developing countries. In Iran, grain yield of wheat reduced by terminal drought stress. Drought stress is one of the most important factors limiting the growth and yield of crops such as wheat as the most important crop in arid and semi-arid regions of the world as well as in Iran. It is growing in a wide range of climatic conditions and plays an important role in Supplying human food needs. This plant is exposed to drought stress at the germination stage and the end of the growth season. Genotypes that can react to drought stress at the germination stage have a better growth in seedlings. The aims of this research is to Investigate the response of the germination components to different levels of drought stress in bread wheat genotypes and also finding drought tolerant genotypes. Materials and methods This research was conducted to study of drought stress treatments on seed characteristics and seedling growth of wheat Thirty wheat genotypes including Mihan, Aroom, Navid, Alvand, Zarrin, Zare, Sison, Alamoot, Gascogen, Heydari, Rizhav, Baran, Karim, Koohdasht, Pishgam, Star, Pishtaz, Qods, Marvdasht, Sardari, Kavir, Dez, Virinak, Alborz, Hirmand, Roshan, Zagros, Bezostaya, Azar and Sirvan. For this propose, a factorial experiment was conducted using 4 levels of osmotic potential (0, -4, -8, -12, -16 bar) using poly ethylene glycol. Seeds were sown on laboratory and data were recorded and analyzed for percent and speed of germination, length of root and shoot, vigor index and fresh and dry weight of seedling. Data analysis was carried out using SAS (Statistical Analysis System ver 9.1), MSTAT-C, SPSS 18 and means were compared using by Duncan's multiple range tests (P< 0.05). Results and discussion In agreement with other studies, drought stress condition significantly decreased All Germination traits with increasing levels of stress. The results showed significant differences among genotypes, drought stresses and genotypes × drought stress interaction for most of traits. In this study, 30 wheat genotypes were exposed to drought stress at flowering stage. The genotype Heidari had higher performance for length of root and percent and speed of germination whereas Azar genotype was the worse. Genotype Sardari had higher performance for seedling vigor index and length of shoot whereas Azar genotype was the worse. Genotype Roshan had higher performance for fresh and dry weight of seedling, while Alvand genotype was the worse. The results in control condition was showed that length of root had the highest positive and significant correlation with percent and speed of germination and germination index and under drought stress condition between all of traits were positive and significant correlation. According to principal component analysis, two main components were selected that in total 72 percent of the total variation was explained. Factors analysis was performed using the studied traits, and two factors( based on specific values larger than one) justify about 72% of the variations in the total data, of which the first factor justifies about 53% of the variations, including traits Root length, stem length, percentage and speed of germination, seed index and germination index, and the second factor, which justifies about 19% of the variation, includes somewhat two traits and seedling dry and fresh weight. Therefore, selection based on these two factors showed the most effect on germination of seeds. In order to determine the variation between different genotypes of different types and determine the relationship between genotypes, cluster analysis using Ward method was performed based on 8 indicators and component of the study. Genetic types of wheat were grouped in 4 clusters with similar intra-group characteristics and non-similar groups. It indicated that 9 genotypes in the first cluster, 14 genotypes in the second cluster, 6 genotypes in the third cluster and Karim genotype were placed alone in the fourth cluster. Information contained in each cluster Groups have led to the identification of genotypes with unique traits and will help us select parental cross-breeds.The fourth cluster (including Karim genotype) had the highest mean and deviation from the mean for root length, percentage and speed of germination, seedling fresh weight and germination index. The third cluster included six genotypes such as Rijaw, Starr, Ghods, Marvdasht, Sardari And bright in terms of stem length, vigor index and seedling dry weight had the highest mean. It can also be argued that the Karim and Heidari genotypes can be used for cross-breeding programs in two separate clusters and maximum genetic distance between them.