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Nonhost Resistance of Barley Is Successfully Manifested Against Magnaporthe grisea and a Closely Related Pennisetum-Infecting Lineage but Is Overcome by Magnaporthe oryzae

September 2006 , Volume 19 , Number  9
Pages  1,014 - 1,022

Nina Zellerhoff , 1 Birgit Jarosch , 1 Johannes Z. Groenewald , 2 Pedro W. Crous , 2 and Ulrich Schaffrath 1

1Department of Plant Physiology, RWTH Aachen University, 52056 Aachen, Germany; 2Centraalbureau voor Schimmelcultures, Fungal Biodiversity Center, 3584 CT Utrecht, The Netherlands

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Accepted 8 May 2006.

Magnaporthe oryzae is a major pathogen of rice (Oryza sativa L.) but is also able to infect other grasses, including barley (Hordeum vulgare L.). Here, we report a study using Magnaporthe isolates collected from other host plant species to evaluate their capacity to infect barley. A nonhost type of resistance was detected in barley against isolates derived from genera Pennisetum (fontaingrass) or Digitaria (crabgrass), but no resistance occurred in response to isolates from rice, genus Eleusine (goosegrass), wheat (Triticum aestivum L.), or maize (Zea mays L.), respectively. Restriction of pathogen growth in the nonhost interaction was investigated microscopically and compared with compatible interactions. Real-time polymerase chain reaction was used to quantify fungal biomass in both types of interaction. The phylogenetic relationship among the Magnaporthe isolates used in this study was investigated by inferring gene trees for fragments of three genes, actin, calmodulin, and β-tubulin. Based on phylogenetic analysis, we could distinguish different species that were strictly correlated with the ability of the isolates to infect barley. We demonstrated that investigating specific host interaction phenotypes for a range of pathogen isolates can accurately highlight genetic diversity within a pathogen population.

Additional keywords: hypersensitive response , MLO , papilla , qPCR , rice blast .

© 2006 The American Phytopathological Society