Inheritance of leaf rust and stripe rust resistance in the Brazilian wheat cultivar Toropi
Barcellos Rosa S, McCallum B, Brule Babel A, Hiebert C, Shorter S, Randhawa H, Barcellos LA (2016) Inheritance of leaf rust and stripe rust resistance in the Brazilian wheat cultivar Toropi. Plant Dis 100: 1132-1137
Plain language summary
Leaf rust is the most wide-spread fungal disease of wheat globally. Leaf rust can cause reductions in grain yield and quality. There are genes in wheat, called leaf rust resistance (Lr) genes, which enable the wheat plant to defend itself from the fungus that causes leaf rust. The fungus evolves over time into difference races or strains that have the ability to overcome some resistance genes. This means that new sources of resistance genes need to be discovered or long-lasting resistance genes should be identified. Toropi is an old South American wheat variety that has maintained its resistance to leaf rust for approximately 50 years. This study analyzed the genetics of leaf rust resistance in Toropi to determine the number of Lr genes present. It was determined that Toropi carries two genes that must be present together (complementary genes) in order to provide resistance to all races of the leaf rust fungus tested. This is called race-nonspecific resistance. An additional gene was found that provides resistance to specific races of leaf rust.
Leaf rust (Puccinia triticina) and stripe rust (P. striiformis f. tritici) affect wheat production worldwide. Brazilian ‘Toropi’ wheat has demonstrated durable leaf rust resistance in South America since its release in 1965. It was previously found to have up to two adult plant leaf rust resistance genes. The leaf and stripe rust resistance of Toropi were studied by analyzing a doubled-haploid population made by crossing with susceptible ‘Thatcher’. Toropi expressed good resistance to leaf rust in Canada, Brazil, and New Zealand. Based on field and greenhouse testing, the leaf rust resistance of Toropi is conferred by two race-nonspecific complementary adult plant genes and a race-specific adult plant gene. The stripe rust resistance of Toropi analyzed in New Zealand and in Canada is based on up to two resistance genes. Toropi should provide an important contribution to rust resistance because it expressed good leaf rust and stripe rust resistance in different parts of the world.