The discovery of barley MLO demonstrated that filamentous pathogens rely on plant genes to achieve entry and lifecycle completion in barley leaves. Whilst having a dramatic effect on foliar pathogens, it is unclear whether overlapping or distinct mechanisms affect filamentous pathogen infection of roots. To remove the bias connected with using different pathogens to understand colonisation mechanisms in different tissues we have utilized the aggressive hemibiotrophic oomycete pathogen Phytophthora palmivora. P. palmivora colonises root as well as leaf tissues of barley (Hordeum vulgare). The infection is characterized by a transient biotrophy phase with formation of haustoria. Barley accessions varied in degree of susceptibility, with some accessions fully resistant to leaf infection. Notably, there was no overall correlation between degree of susceptibility in roots compared to leaves suggesting that variation in different genes influences host susceptibility above- and belowground. In addition, a developmental gradient influenced infection, with more extensive colonisation observed in mature leaf sectors. Only in young leaf tissues, the mlo5 mutation attenuates P. palmivora infection. The barley - P. palmivora interaction represents a simple system to identify and compare genetic components governing quantitative colonisation in diverse types of barley tissues.
Via Kamoun Lab @ TSL