Study of drought tolerance in a wheat mutant line at the germination and adult stages

Introduction The world population is predicted to increase beyond 8 billion by 2030 implying major challenges for agricultural sector to secure food availability (Smol JP , 2012).Wheat is one of the main cereal crops, cultivated to meet great demands of the population for human feeding. It is the most important staple for bread flour in Iran (Nour- mohamadi et al., 2009). A key challenge for plant growth is global water shortage (Flexas et al., 2013; Foley et al., 2011). A variety of strategies has been used to improve the drought tolerance of crops, including traditional selection methods and genetic engineering (Fleury et al., 2010). In this case, irradiation is an appropriate approach for improving the level of genetic variation a short time. Materials and methods This study was carried out to determine the response of mutant line# 'T65588' derived from 'Tabasi' radiated with Gamma rays to drought stress. Germination traits were investigated in osmotic stress induced by PEG and water related traits studied in drought stress at adult wheat stage both under completely randomized design with three replications. Results and discussion The results of analysis of variance indicated that germination features were intensely affected by the PEG treatment. Also genotypes differed significantly for germination rate, plumule length and radicle length. Significant drought stress × genotype effect in germination rate, plumule length, radicle length and plumule dry weight indicated that reaction of genotypes to polyethilenglycol was not simmilar. Drought significantly influenced water-related variables- RWC, RWL and ELWR- traits and caused depletion in RWL and increasing in RWC and ELWR. Conclusions Mutant line# 'T65588' in germination features had superiority on its wild genotype ('Tabasi') in drought stress conditions. Persistence in RWC content of cultivars in water stress conditions may serve as good indicator of drought tolerance. As mentioned above, the rate of increasing in RWC for mutant line#'T65588' was more than 'Tabasi'. RWC is closely related to cell volume, therefore it may more closely reflect the balance between water supply to the leaf and transpiration rate (Farquhar et al., 1989).  Schonfeld et al (1988) observed a decline in the amount of RWC in wheat due to drought stress and reported the highest RWC in the tolerant genotype. Several researchers have shown that low rate of water loss (RWL) from excised leaves are related to drought resistance, and may be used as screening criteria in breeding programs (Winter et al., 1988). Our result is consistent with Golestani Araghi and Asad (1998) findings, who observed decrease in the RWL under stress condition in wheat. Big reduction in RWL in  mutant line may indicate the more efficient use of water by 'T65588' mutant genotype. Based on Lonbani  and Arzani (2011) suggestion, among the plant water relation parameters, ELWR could be a superior indirect selection criterion for grain yield. This trait is moderately heritable (Clarke and Townley-Smith, 1986) and can be easily estimated in a large population (Dhanda and Sethi, 1998). The rate of increasing in ELWR in mutant line#'T65588' in comparison to its wild variety ('Tabasi') was more, which is an another validation for assertion of Mutant line# 'T65588' in germination features and also water-related variables in adult plant had superiority on its wild genotype in drought stress conditions.