Genetic basis of spring wheat resistance to leaf rust (Puccinia triticina) in Kazakhstan and Russia

Kazakhstan-Siberia Network for Spring Wheat Improvement (KASIB) was established in 2000 to conduct multi-location cooperative yield trials for the exchange of breeding material and to evaluate agronomic traits such as grain yield and disease resistance. In 2016, aggregated KASIB data were analyzed and 120 cultivars and breeding lines demonstrating different degrees of resistance to leaf rust selected. They were tested for leaf rust and agronomic traits in Omsk, Russia; Almaty, Kazakhstan and Sakarya, Turkey in 2017–2019. This germplasm was grouped into four categories based on leaf rust reaction: 31 resistant (R), 27 moderately resistant (MR), 37 intermediate (M) and 25 moderately susceptible (MS) entries. Lr genes were postulated based on tests using pathotypes with known virulence profiles and molecular markers. The most frequent Lr genes alone or in combination were Lr10 (31 entries), Lr26 (24), Lr9 (23), Lr1 (18), Lr17 (11), Lr34 (11) and Lr19 (7). Genes Lr1, Lr9, Lr10 and Lr17 reduced the leaf rust severity to M or MS across environments. The presence of Lr26 alone or in combination with other major genes reduced the leaf rust severity to MR-M in Omsk and R in Sakarya. The only gene with the large effect on leaf rust was Lr19, which provided a high level of resistance at all sites both alone and in combination with Lr26. Leaf rust severity in 52 entries with adult plant resistance (APR) was compared to 68 entries possessing effective seedling resistance genes. The leaf rust severity in entries with APR compared to seedling resistance was similar at low infection pressure at Sakarya, 2018 and Omsk, 2019. However, at higher leaf rust infection pressure at Omsk in 2017 and 2018, Almaty in 2019, there was a clear advantage for the germplasm possessing major genes. High level of stem rust infection in Omsk in 2019 confirmed effectiveness of the Sr31/Lr26 gene. A set of 33 genotypes was selected combining resistance to leaf and stem rust with superior agronomic performance.