Identification of Leaf Rust Resistance Genes in Bread Wheat Cultivars from Ethiopia.

Wheat leaf rust, caused by Puccinia triticina (Pt), is a widespread disease of bread wheat worldwide. In the present study, 50 wheat cultivars from Ethiopia and 34 differential lines, mostly near-isogenic lines (NILs) in the background of Thatcher with known resistance genes to leaf rust (Lr), were tested with 14 Pt races in the greenhouse to postulate Lr genes at the seedling stage. Field experiments were also conducted to identify adult plant responses to leaf rust in Baoding in the 2017-2018 and 2018-2019 growing seasons and in Zhoukou in the 2018-2019 growing season. Thirteen Lr genes (Lr1, Lr18, Lr3ka, Lr15, Lr26, Lr20, Lr14a, Lr30, Lr2a, Lr11, Lr34, Lr46, and Lr68) either singly or in combination were found in 39 cultivars. Known Lr genes were not present in the remaining 11 cultivars. Lr1 and Lr46, each in 13 cultivars, and Lr34 in 12 cultivars were the most commonly identified resistance genes. Less frequently identified genes included Lr26 (five cultivars); Lr30 and Lr18 (each present in four cultivars); Lr15, Lr3ka, and Lr2a (each identified in three cultivars); and Lr68 (two cultivars). Evidence for the existence of Lr11, Lr20, and Lr14a (each in one cultivar) was also obtained. Twenty-one cultivars were found to have slow rusting resistance to leaf rust in the field tests. The results should be valuable for cultivar selection with combinations of effective Lr genes and used in breeding new cultivars with improved resistance to leaf rust in Ethiopia and China.

Identification of Leaf Rust Resistance Genes in Chinese Common Wheat Cultivars.

Puccinia triticina Eriks. (Pt), the causal agent of wheat (Triticum aestivum L.) leaf rust, is the most widespread disease of common wheat worldwide. In the present study, 83 wheat cultivars from three provinces of China and 36 tester lines with known leaf rust resistance (Lr) genes were inoculated in the greenhouse with 18 Pt pathotypes to identify seedling effective Lr genes. Field tests were also performed to characterize slow leaf rusting responses at the adult plant growth stage in Baoding and Zhoukou in the 2014-15 and 2015-16 cropping seasons. Twelve Lr genes, viz. Lr1, Lr26, Lr3ka, Lr11, Lr10, Lr2b, Lr13, Lr21, Lr34, Lr37, Lr44, and Lr46 either singly or in combination were identified in 41 cultivars. Known Lr genes were not detected in the remaining 42 cultivars. The most commonly identified resistance genes were Lr26 (20 cultivars), Lr46 (18 cultivars), and Lr1 (eight cultivars). Less frequently detected genes included Lr13, Lr34, and Lr37 (each present in four cultivars), Lr10 (three cultivars), and Lr3ka and Lr44 (each in two cultivars). Evidence for the presence of genes Lr11, Lr2b, and Lr21 (each in one cultivar) was also obtained. Seventeen cultivars were found to have slow rusting resistance in both field growing seasons.