Exploring the suitable concentration and time of EMS mutagen on chia seed germination (Salvia hispanica L.)

Introduction: Chia (Salvia hispanica L.) is an annual, diploid (n=۱۲) and self-pollinated herbaceous plant from the Lamiaceae family (Bochicchio et al., ۲۰۱۵). Its main origin is between Mexico and Guatemala. It is an expensive plant that natives have used for medicine, food and oil since the past, but its cultivation is due to short day flowering, high sensitivity to changes in photoperiods and weakly cold tolerance, stopped and became an unknown species within a hundred years (Jamboonsri et al., ۲۰۱۲). Chia mature seeds contain ۲۵-۴۰% oil, of which ۶۰% is alpha-linolenic acid or omega-۳ (ω۳) and ۲۰% is linoleic acid or omega-۶ (ω۶), ۶-۲۶% protein and ۳۶-۴۰% of total dietary fiber. Also, chia seeds contain carbohydrates and fiber, vitamins including B vitamins (B۱, B۲, B۳, B۶, and B۹), A, C, K, and E, minerals such as magnesium, zinc, iron, calcium, potassium and phosphorus (Mehta et al., ۲۰۲۰; Suri et al., ۲۰۱۶). There are many techniques for breeding plants. Breeding by mutation is one of these methods. Usually, physical and chemical mutagens are widely used to create new changes in germplasm or induce random genetic changes in crops (Siddique et al., ۲۰۲۰). Alkylating agents have been used as chemical mutagens in plants for many years because they are the most successful chemical mutagens for generating new plant mutants. Considering the low genetic diversity of chia germplasm, other methods such as mutation can be used to create new cultivars and find genetic diversity. Ethyl methane sulfonate (EMS) is the most widely used chemical mutagen to induce mutations in seeds and loci that regulate essential economic traits. It generates high-frequency random point mutations, some of which can create new stop codons in the target genes. Additionally, it can knock down genes and it will help researches that identify the role of genes through analysis of mutant phenotypes (Arisha et al., ۲۰۱۴). In separate studies, Jamboonsri et al. (۲۰۱۲), Hildebrand et al. (۲۰۱۳) and Thaboran et al. (۲۰۲۰) used EMS and gamma radiation to mutagenize chia seeds to produce early flowering chia mutants. The goal of this experiment was finding the suitable concentration and time of soaking the seeds in EMS which caused ۵۰% reduction in germination percentage of chia seeds in order to apply that concentration and duration for induction mutation in the future. Materials and methods: In this research, in order to determine the concentration and time of seed soaking in EMS, which is used as a chia mutagen on seed germination, root and shoot growth, a factorial experiment based on a randomized completely design (CRD) was conducted in three replications. Factor A was two genotypes of chia seed (۱ and ۲), factor B was concentration of mutagen at four levels (۰, ۱, ۳ and ۶%) and factor C considered as three levels of duration of exposure to mutagen (۶, ۹ and ۱۲ hours). Seed germination percentage, root and shoot length, fresh and dry weights of root and shoot were evaluated after ۲۱ days after treating and comprised with the untreated seeds. Data were analyzed with MSTATC software. Results and Discussion: According to the observation of the test process in the laboratory, it was clear that EMS reduced seed germination. So, with the increase in the concentration of the mutagenic substance and also the time of immersing the seeds in the mutagenic substance, the rate of seed germination has decreased more. According to the analysis of variance (Table ۱), all three cases of genotype, concentration of mutagen and treatment time had a significant effect on germination percentage. The mean comparison results based on a LSD test at P = ۰.۰۵ (table ۲, Figure ۱) showed that the concentration of ۳% and ۶% EMS in a period of ۶ hours caused a decrease in germination percentage (۵۸.۸۹% and ۵۴.۴۵% respectively) for genotype ۲ and a concentration of ۶% in a period time of ۶ hours caused a decrease (۱۵.۵۶%) in germination of genotype ۱. The obtained results were consistent with the results of the Jamboonsri et al. (۲۰۱۲) and Hildebrand et al. (۲۰۱۳).

کلیدواژه ها:

Chia ، Salvia hispanica ، mutagen ، EMS ، seed germination ، genetic diversity ، mutation ، ethyl methane sulfonate ، seed soaking ، root growth ، shoot growth