Inducing mutations in bread wheat (Triticum aestivum L.) using chemical treatments

[摘要] ENGLISH ABSTRACT: Bread wheat (Triticum aestivum L.) production is hindered by a variety of abiotic stresses withdrought being the most devastating. Mutation breeding through induced mutagenesis is one wayfor wheat breeders to adapt to the challenges posed by climate change. Especially, chemicallyinduced mutagenesis showed promise in improving drought tolerance using differentrecommended mutagens at optimum concentrations and treatment durations. The aim of thestudy was to improve drought tolerance in wheat by means of chemical induced mutagenesis. Inthe study, the mutagenic properties of four chemicals, namely Sodium azide (SA, 0.1 mM, 1.0mM and 10 mM), Ethyl methanesulfonate (EMS, 0.1%, 0.5%, 1.0% v/v), Maleic hydrazide (MH,0.5 mM, 1.0 mM, 2.0 mM), and N-methyl-N-nitrosourea (MNU, 0.5 mM, 1.0 mM, 2.0 mM) atdifferent concentrations and treatment durations (2h, 4h and 8h) were compared. To select formutants that express drought tolerance, the M1 plants were exposed to water stress. NMU andMH treated M1 plants demonstrated zero survival rates, while a few of the plants treated with SAand EMS survived. In the study, treatments with 0.5% (EMS) 4h, 1% (EMS) 2h, 1 mM (SA) 2hand 1 mM (SA) 8h were considered optimum, since these treatments resulted in fertile plants.However, the chemically derived mutant wheat lines displayed a lower germination rate, delayedmaturity, stunted growth and lower than average seed mass when compared to the control. Thelatter traits were also verified in the M2 and M3 generations. The M2 and M3 generations alsodisplayed a shorter growth form and delayed maturity phenotype, but had higher germinationrates and produced more seeds. Screening for drought tolerance conducted on the M3 plantsconfirmed the tolerant phenotype found in the M1 generation plants. Amplified fragment lengthpolymorphism (AFLP) profiling was also conducted on the mutants using three primercombinations (MTT/ECG, MTG/ECT and MTG/EGC) in order to assess the extent andsignificance of the induced mutations. From the obtained data, it was revealed that SA 1 mM(2h) 16 had the highest number of induced total character differences (109) relative to the control of all the SA and EMS derived mutants, suggesting that a treatment with 1 mM SA for 2hinduced more mutations than any other SA or any of the EMS treatments. Of the sequencedclones, only one revealed similarity to a T. aestivum isolate AAC/CTG7 scab resistance-linked AFLP fragment gene sequence, an important disease of wheat, but due to time constrains thisfinding was not investigated further.

[发布机构] Stellenbosch University