Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 8/10/2013
Publication Date: 8/18/2013
Citation: Chen, X. 2013. Virulences, population structures and genomics of Puccinia striiformis and interactions with its plant hosts. Meeting Abstract. 3rd International Conference on Biotic Plant Interactions, Yangling, China. Pg. 40.
Interpretive Summary: This invited talk presents our recent progress on reproduction modes, virulence, population structure and evolutional relationships of the stripe rust pathogen and its interactions with various hosts. The wheat stripe rust pathogen can infect wheat as primary host and more than 200 grass species as auxiliary hosts by its asexually reproduced spores and infect barberry and mahonia as alternate hosts by sexually reproduced spores. The wheat and barley stripe rust pathogens can hybridize to produce isolates attacking some varieties of the two crops. More than 150 wheat stripe rust races have been identified using a set of wheat variety differentials and more than 80 barley stripe rust races using a set of barley differentials. From 2010, we have used a new set of single resistance-gene lines to identify more than 70 races, which directly indicate interactions between individual resistance genes and avirulence genes. The whole genome and several cDNA libraries of the wheat stripe rust pathogen were sequenced, based on which molecular markers were developed and used to study the rust population structures. Various studies revealed heterokayotic variation, mutation, and somatic hybridization as mechanisms for the pathogen evolution. Global and US population studies identified two distinct genetic clusters and revealed gene flow among countries and continents. Our studies did not indicate any role of alternate hosts to stripe rust under natural conditions, but we have developed a system with alternate hosts to study the pathogen genetics.
Technical Abstract: Puccinia striiformis, an obligate biotrophic fungal species, has different formae speciales primarily infect wheat, barley, and grasses. The forma specialis P. striiformis f. sp. tritici (Pst) causes one of the most important diseases of wheat in the world. In addition to its primary host of wheat, Pst can infect more than 200 grass species, which are considered as auxiliary hosts, by its asexually reproduced urediniospores and species of Berberis and Mahonia, which are considered as alternate hosts, by sexually reproduced basidiospores. Studies of natural populations collected from wheat, barley and grasses and artificially generated isolates by infection of wheat and barley plants with mixed spores of Pst and P. striiformis f. sp. hordei (Psh, the barley stripe rust pathogen) under controlled greenhouse conditions revealed that Pst and Psh can hybridize to produce isolates which can attack wheat and barley varieties. More than 150 Pst races have been identified using a set of wheat variety differentials since 1960s and more than 80 Psh races identified using a set of barley differentials since 1990s. From 2010, we have used a set of Yr single-gene lines as Pst differentials and identified more than 70 races, which directly indicate interactions between individual resistance genes and avirulence genes. The whole genome and several cDNA libraries of Pst were sequenced. Molecular markers developed based on cDNA and genomic sequences were used to study Pst population structures. Studies using SSR markers and specific gene sequences revealed heterokayotic variation, mutation, and somatic hybridization as mechanisms for Pst evolution. Global and US population studies identified two distinct genetic clusters and revealed gene flow among countries and continents. Population studies with both Pst samples from wheat crops and Puccinia aecial samples from barberry plants in the U.S. Pacific Northwest did not support any role of alternate hosts to stripe rust epidemic and Pst variation. However, we have developed a system with Berberis and Mahonia spp. to study genetics of Pst virulence. We used the transcriptomics approach to identify Pst genes involved in the infection process in both compatible and incompatible interactions. We developed SNP markers based on secreted protein genes of Pst to study virulence genes. Similarly, we also used the microarray technique to determine defense genes involved in different types of resistance controlled by various resistance genes. With the genotyping by sequencing technique, we are studying both host and pathogen genes involved in the plant-pathogen interactions simultaneously.