Browsing by Author "De Wet, Sumari"
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- ItemRust and FHB improvement of wheat through marker assisted selection and phenotyping(Stellenbosch : Stellenbosch University, 2021-12) De Wet, Sumari; Botes, Willem; Rose, Lindy J. ; Stellenbosch University. Faculty of AgriSciences. Dept. of Genetics.ENGLISH ABSTRACT: Wheat is one of the most widely cultivated crops of significant economic and nutritional importance. The predicted growth of the human population will result in higher food demands in the future. Wheat yield needs to sustainably increase to maintain food security. Unfortunately, the productivity of wheat are negatively impacted by abiotic and biotic stressors. Rust (leaf, stem and stripe) are the most prevalent disease on wheat that can cause severe damage to global production. Wheat rusts are caused by Puccinia spp. that are widely spread and highly adaptable. Fusarium head blight (FHB) on wheat is caused by Fusarium species that forms a complex that can produce mycotoxins in infected seeds. The FHB disease on wheat can result in reduction of seed quality and yield. One of the most important management factors to solve the problems posed by rust and FHB is by breeding for host plant resistance. Genetic resistance can be improved by using different rust and FHB resistance sources to achieve durable resistance. The aim of this study was to generate molecular and phenotypic data of wheat lines to evaluate resistance to rust and FHB for improvement of genetic resistant material. An existing male sterile segregating MS-MARS population together with donor populations were screened for markers linked to rust and FHB resistance. Wheat lines that contained desirable traits were selected as parents in two breeding cycles of the male sterile mediated marker-assisted recurrent selection (MS-MARS) pre-breeding program. The donor lines were further evaluated by rust field phenotyping and FHB phenotyping under glasshouse conditions. The molecular markers were successfully implemented to molecular characterise the populations and assisted in the parent selection process. The frequencies of two important slow rusting genes, Sr2 and Lr34, were increased by 1.67% and 10.00%. The crossing cycles produced a large number of 3919 (cycle 1) and 9716 (cycle 2) hybrid seeds. Rust field evaluations enabled identifying wheat lines that showed low susceptible phenotypic responses (20S to 40S) to leaf rust disease. Successful inoculations with Fusarium graminearum isolates were performed and disease severity between 13% and 100% were measured on 21 days post inoculation. The liquid chromatography tandem mass spectrometry (LC-MS/MS) technique detected deoxynivalenol (DON) contamination levels above 0.032 ppb in fourteen wheat samples. Future studies should aim at screening germplasms for the presence of more molecular markers linked to rust and FHB resistance. Selection of breeding parents should be based on both molecular data as well as phenotype data collected over multiple wheat growing seasons to improve effectiveness of resistance breeding.