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Phenotypic and genotypic evaluation of wheat genetic resources and development of segregating populations are pre-requisites for identifying rust resistance genes. The objectives of this study were to assess adult plant resistance (APR) of selected wheat genotypes to leaf rust and stem rust and to develop segregating populations for resistance breeding. Eight selected Kenyan cultivars with known resistance to stem rust, together with local checks were evaluated for leaf rust and stem rust resistance at seedling stage and also across several environments. Selected diagnostic markers were used to determine the presence of known genes. All eight cultivars were crossed with local checks using a bi-parental mating design. Seedling tests revealed that parents exhibited differential infection types against wheat rust races. Cultivars Paka and Popo consistently showed resistant infection types at seedling stage, while Gem, Romany, Pasa, Fahari, Kudu, Ngiri and Kariega varied for resistant and susceptible infection types depending on the pathogen race used. The control cultivars Morocco and McNair consistently showed susceptible infection types as expected. In the field, all cultivars except for Morocco showed moderate to high levels of resistance, indicating the presence of effective resistance genes. Using diagnostic markers, presence of Lr34 was confirmed in Gem, Fahari, Kudu, Ngiri and Kariega, while Sr2 was present in Gem, Romany, Paka and Kudu. Seedling resistance gene, Sr35, was only detected in cultivar Popo. Overall, the study developed 909 F6:8 recombinant inbred lines (RILs) as part of the nested mating design and are useful genetic resources for further studies and for mapping wheat rust resistance genes. [ABSTRACT FROM AUTHOR]

Cultivated barley (Hordeum vulgare) is an important winter cereal in South Africa (SA), ranked second after wheat. Leaf rust, caused by Puccinia hordei Otth. (Ph), is one of the most common diseases affecting grain yield and quality of barley. In this study, isolates of Ph were pathotyped using differential cultivars and lines with designated Rph -resistance genes, as well as a set of Bowman introgression lines (BW) containing resistance genes Rph1 to Rph15. Single pustule isolates derived from recently collected field isolates, typed as Ph race UVPh7235, showed increased virulence to Rph3 when compared with previously described races from SA. Discrepancies in phenotypic responses were recorded between standard differential lines carrying Rph2 , Rph6 and Rph9 and the corresponding BW lines. Results for barley cultivars with designated sources of adult plant resistance revealed low seedling infection types (ITs) for Baronesse (Rph20 + Rph24) to all Ph isolates and for Lenka (Rph20 + Rph23 + Rph24) to isolates of Ph races UVPh3231 and UVPh7231. The barley cultivars Agulhas and Cristalia showed low seedling ITs and moderate to high levels of adult plant resistance under field and greenhouse conditions, respectively. Genotyping of 48 Ph isolates with 20 microsatellite markers revealed five closely related genetic lineages with low gene diversity and allelic richness levels. While STRUCTURE analysis revealed three clusters, no clear division of the isolates into the clusters was evident, as the isolates were admixed for all three. Linkage disequilibrium analysis, as well as higher H O versus H E values, supported the hypothesis that the South African Ph population is clonal, consisting of a single genetic lineage. • New race of barley leaf rust caused by Puccinia hordei. • Barley cultivar responses to leaf rust. • Microsatellite marker analysis revealed low gene diversity and allelic richness. • Propagation of Puccinia hordei appears to be clonal in South Africa. [ABSTRACT FROM AUTHOR]