Genetic analysis and molecular mapping of resistance in barley to the heterologous rust pathogens Puccinia graminis f. sp. avenae and P. triticina

Stem rust is considered one of the most important threats to world cereal production. The appearance and spread of the wheat stem rust pathogen [Puccinia graminis f. sp. tritici (Pgt)] race Ug99 has caused great concern for global wheat production. Barley is a host to different specialized pathogen species such as Pgt, but is characteristically a near nonhost to most non-adapted (heterologous) rust pathogens such as the wheat leaf rust pathogen [P. triticina] and oat stem rust pathogen [P. graminis f. sp. avenae (Pga)]. The barley research line SusPtrit, developed for susceptibility to heterologous rust pathogens, is a useful resource to study the genetics of nonhost resistance and to clone the genes involved, particularly due to the recent availability of the genome sequence. Studies in wheat suggest that resistance genes that are effective against multiple rust pathogens (pleiotropic) such as Lr34/Yr18/Sr55, confer durable disease control. We intercrossed the sequenced barley genotype Morex with SusPtrit to determine the inheritance of resistance to the wheat leaf rust and oat stem rust pathogens. The F2 population segregated for a single dominant resistance gene in response to both heterologous pathogens Pga and Pt. Subsequent progeny testing and genetic analysis of the segregating F3 population will be performed to map and determine the relationship between the resistance genes. Large F2 populations were developed to fine map and clone the genes, and ultimately to transfer them into related crop species as an alternative approach for crop protection.

The University of Sydney, Plant Breeding Institute, Australia
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