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Molecular Marker Mapping of Leaf Rust Resistance Gene Lr46 and Its Association with Stripe Rust Resistance Gene Yr29 in Wheat

First, second, fourth, and fifth authors: International Maize and Wheat Improvement Center (CIMMYT), Apartado Postal 6-641, 06600, Mexico, D.F.; third author: Campo Experimental Valle de Mexico-INIFAP, Apdo. Postal 10, 56230, Chapingo, Edo. de Mexico; and first and fifth authors: Cooperative Research Center for Molecular Plant Breeding, Australia

Leaf and stripe rusts, caused by Puccinia triticina and P. striiformis, respectively, are globally important fungal diseases of wheat that cause significant annual yield losses. A gene that confers slow rusting resistance to leaf rust, designated as Lr46, has recently been located on wheat chromosome 1B. The objectives of our study were to establish the precise genomic location of gene Lr46 using molecular approaches and to determine if there was an association of this locus with adult plant resistance to stripe rust. A population of 146 F₅ and F₆ lines produced from the cross of susceptible ‘Avocet S’ with resistant ‘Pavon 76’ was developed and classified for leaf rust and stripe rust severity for three seasons. Using patterns of segregation for the two diseases, we estimated that at least two genes with additive effects conferred resistance to leaf rust and three to four genes conferred resistance to stripe rust. Bulked segregant analysis and linkage mapping using amplified fragment length polymorphisms with the ‘Avocet’ × ‘Pavon 76’ population, F₃ progeny lines of a single chromosome recombinant line population from the cross ‘Lalbahadur’ × ‘Lalbahadur (Pavon 1B)’, and the International Triticeae Mapping Initiative population established the genomic location of Lr46 at the distal end of the long arm of wheat chromosome 1B. A gene that is closely linked to Lr46 and confers moderate levels of adult plant resistance to stripe rust is identified and designated as Yr29.

Additional keywords: Triticum aestivum.