Title: Screening of EMS mutant lines for drought tolerance in the seedling stage
Author: Leila Khazaie
Abstract: Abiotic stresses, especially drought, have a negative effect on crop growth and production. Non-availability of high-yielding varieties suitable for cultivation under drought condition lead to a sharp decline in rice yield. Induce mutation is an auxiliary breeding approach along with conventional breeding to produce stress-tolerance rice variety. The current study was aimed to identify mutant rice genotypes as drought-tolerant using growth parameters in the seedling. First, Hashemi rice seed treated with 0.8% ethyl methanesulfonate (EMS) for 8 hours, and Mutant seeds of Hashemi local cultivar (M1) were sown separately in the form of a single plant with control cultivar (non-mutant) and at the end of the crop season, the seeds of each plant were harvested separately. Then, Mutant seeds (M2) with parent cultivar were sowed in the form of the observational design at the research fields of the Rice Research Institute of Iran and 309 M2 plants were evaluated in terms of the phenotypic diversity of traits and due to select the appropriate plants. After evaluation, 41 of the M3 mutant plants were selected with optimal genetic diversity compared to Hashemi parents. Then, Study the effect of drought stress on some of the morphological traits of M3 41 selected mutant seedling along with Hashemi parent cultivar by polyethylene glycol 6000 in -10 bar level was performed in a completely randomized factorial design. Results of analysis of variance showed that the effect of drought, genotype, and genotype on drought interaction on shoot length, root length, root fresh weight, stem fresh weight, stem dry weight, root dry weight and root length to stem ratio, root fresh weight to shoot fresh weight ratio and root dry weight to shoot dry weight ratio was significant. Based on the results of the phenotypic evaluation of the mutant genotypes was found that these genotypes are appropriate diversity to drought stress and respond to environmental stress. Due to the positive, significant, and high correlation of indices STI with HMP and MP with GMP in both environments, it seems that the use of these indices can help the selection of tolerant mutant genotypes under water deficit conditions. According to M29, M122, M284 mutant genotypes had the best yield in the fresh and dry root, fresh and dry stem weight, stem length, and root length at stress level and were identified as the most tolerant genotypes. Also, M31, M106, and M204 mutant genotypes were introduced as the most susceptible genotype with the lowest tolerance at stress level.
Drought, EMS, Phenotypic Diversity, Polyethylene Glycol, Mutation, Rice, Stress Index