Browsing by Author "Mbwanji, Kenneth"
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- ItemInducing mutations in bread wheat (Triticum aestivum L.) using chemical treatments(Stellenbosch : Stellenbosch University, 2014-12) Mbwanji, Kenneth; Botha-Oberholster, Anna-Maria; Stellenbosch University. Faculty of AgriSciences. Dept. of Genetics.ENGLISH ABSTRACT: Bread wheat (Triticum aestivum L.) production is hindered by a variety of abiotic stresses with drought being the most devastating. Mutation breeding through induced mutagenesis is one way for wheat breeders to adapt to the challenges posed by climate change. Especially, chemically induced mutagenesis showed promise in improving drought tolerance using different recommended mutagens at optimum concentrations and treatment durations. The aim of the study was to improve drought tolerance in wheat by means of chemical induced mutagenesis. In the study, the mutagenic properties of four chemicals, namely Sodium azide (SA, 0.1 mM, 1.0 mM 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) at different concentrations and treatment durations (2h, 4h and 8h) were compared. To select for mutants that express drought tolerance, the M1 plants were exposed to water stress. NMU and MH treated M1 plants demonstrated zero survival rates, while a few of the plants treated with SA and EMS survived. In the study, treatments with 0.5% (EMS) 4h, 1% (EMS) 2h, 1 mM (SA) 2h and 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, delayed maturity, stunted growth and lower than average seed mass when compared to the control. The latter traits were also verified in the M2 and M3 generations. The M2 and M3 generations also displayed a shorter growth form and delayed maturity phenotype, but had higher germination rates and produced more seeds. Screening for drought tolerance conducted on the M3 plants confirmed the tolerant phenotype found in the M1 generation plants. Amplified fragment length polymorphism (AFLP) profiling was also conducted on the mutants using three primer combinations (MTT/ECG, MTG/ECT and MTG/EGC) in order to assess the extent and significance 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 2h induced more mutations than any other SA or any of the EMS treatments. Of the sequenced clones, 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 this finding was not investigated further.