Stripe rust and leaf rust are two most widely distributed diseases of wheat despite the fact that major emphasis has been made globally to develop rust resistant varieties. The wild tetraploid wheat Triticum araraticum (AAGG) evolved in the eastern part of Fertile Crescent is a source of useful traits for the improvement of wheat including resistance to disease. T. araraticum acc. pau4692 and a derived advanced backcross introgression line (IL) in susceptible T. durum cv. Malvi local background showed high level of seedling resistance against Indian pathotypes of leaf rust and stripe rust. The F5 Single seed descent (SSD) population developed from the crosses between T. araraticum IL with T. durum cultivar PBW114 was screened with commonly prevalent pathotypes of leaf rust and stripe rust in India at the seedling stage. The genetic analysis indicated that the leaf rust resistance is conditioned by two genes and stripe rust resistance by a single gene. The SSR markers mapped on A and B genome were used for parental polymorphism along with resistant and susceptible bulks for leaf rust and polymorphic markers between bulks were used on the whole population. The molecular marker data using single marker analysis showed that leaf rust resistance genes were mapped on chromosome 2A and 7A linked to SSR markers Xwmc149 and Xbarc49, respectively. The genes have been temporarily named as LrAr1 and LrAr2. Bulked segregant analysis (BSA) for mapping stripe rust resistance is in progress.
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Leaf rust is a common wheat disease in South Africa. Annual surveys conducted by the Agricultural Research Council - Small Grain Institute (ARC-SGI) during the last 35 years used infection type (IT) data on a defined differential set to identify individual field isolates. Results from these surveys confirmed that the South African Pt population is affected by both local evolution and foreign introductions. A good correlation was found between avirulence/virulence phenotypes and simple sequence repeat (SSR) genotypes in the South African Pt population. We therefore evaluated whether identification of field isolates by SSR analysis would complement the traditional IT analysis using 47 field isolates collected during the 2013 growing season. Of the 39 phenotyped isolates, 35 were correctly genotyped while three were incorrectly genotyped only because the corresponding race was not included as a control. Five isolates that could not be phenotyped due to non-viable spores were successfully genotyped. The dominant race 3SA145 (North American race annotation CCPS) was represented by nine different genotypes sharing 82% genetic similarity. The SSR data further showed that the field isolates formed part of two distinct lineages with little admixture between them. This study confirmed the supporting value of SSR genotyping to traditional race analysis in monitoring the South African Pt population.