Phenotyping and Identification of Molecular Markers Associated with Leaf Rust Resistance in the Wheat Germplasm from Kazakhstan, CIMMYT and ICARDA.

Leaf rust (LR) is the most widespread disease of common wheat worldwide. In order to evaluate leaf rust resistance, 70 uncharacterized wheat cultivars and promising lines with unknown leaf rust resistance genes ( genes) were exposed to Kazakhstani () races at the seedling stage. Field tests were performed to characterize leaf rust responses at the adult plant growth stage in the 2020-2021 and 2021-2022 cropping seasons. The wheat collection showed phenotypic diversity when tested with two virulent races of . Thirteen wheat genotypes (18.6%) showed high resistance at both seedling and adult plant stages. In most cases, breeding material originating from international nurseries showed higher resistance to LR. Nine genes, viz. , , , , , , , , and either singly or in combination, were identified in 47 genotypes. Known genes were not detected in the remaining 23 genotypes. The most commonly identified resistance genes were (17 cultivars), (16 cultivars), and (10 cultivars), while , , , and were the least frequent. Four genes were identified in Keremet and Hisorok, followed by three genes in Aliya, Rasad, Reke, Mataj, Egana and Almaly/Obri. The molecular screening revealed twenty-nine carriers of a single gene, ten carriers of two genes, six carriers of three genes, and two carriers of four genes. Most of these accessions showed a high and moderate level of APR (Adult plant resistance) and may be utilized for the incorporation of genes in well-adapted wheat cultivars. The most effective combination was , , and , the carriers of which were characterized by a low disease susceptibility index. The obtained results will facilitate breeding programs for wheat resistance in Kazakhstan.