Wheat Leaf Rust, Caused by <i>Puccinia triticina</i> , and Mitigation Through Host Genetic Resistance

Abstract The obligate fungal pathogen Puccinia triticina causes leaf rust symptoms on wheat worldwide. Epidemics of leaf rust occur during periods of mild weather with high relative humidity. The pathogen infects leaves, causing orange to red pustules, containing millions of urediniospores, reducing the photosynthetic area and causing desiccation and yield loss. Wind-borne urediniospores are produced in continuous asexual cycles on wheat plants. Genetic resistance is the primary control strategy. There are over 80 known leaf rust ( Lr ) resistance genes, and most are race-specific and are active from the seedling stage to maturity. A few Lr genes are nonrace-specific and confer partial resistance to leaf rust and other diseases at the adult plant stage. Combining Lr genes that confer seedling and adult plant resistance has been particularly successful and durable. Pathogen populations are genetically diverse, and races evolve continuously to evade recognition by Lr genes. This results in boom-and-bust cycles when new cultivars with race-specific Lr genes are resistant for some years, but become susceptible, due to evolution of the P. triticina population. Surveillance of P. triticina for the evolution of races helps to develop wheat cultivars with Lr genes that will be resistant to the most prevalent races. Information © The Authors 2024