W358 Non-host resistance to cereal rusts

Date: Saturday, January 14, 2012
Time: 4:30 PM
Room: Pacific Salon 1
Michael Ayliffe , CSIRO Plant Industry, Canberra, Australia
Davinder Singh , The University of Sydney, Camden, NSW, Australia
Robert Park , The University of Sydney, Camden, NSW, Australia
Tony Pryor , CSIRO Plant Industry, Canberra, Australia
Hei Leung , International Rice Research Institute, Plant Breeding, Genetics and Biotechnology Division, Los Banos, Philippines
Plant nonhost resistance (NHR) to nonadapted pathogens is manifested in a variety of ways ranging from basic incompatibility to active defense mechanisms. We have been investigating the infection of cereal rusts on two nonhost species, rice and Brachypodium distachyon. These two species differ in that rice is unique amongst agricultural cereals in being a nonhost to all rust species, whereas Brachypodium distachyon is a host to Puccinia brachypodii. Infection of rice with several cereal rust species (Puccinia graminis f. sp tritici, P. triticina, P. striiformis, and P. hordei) results in the production of large infection sites with many haustoria at some sites for each rust species examined, although sporulation is never observed. Rice responds with an active defense response that shows genetic variation for the efficacy of this response and this NHR is not compromised by mutations in either basal resistance or known defense genes. Brachypodium also shows genetic variation in NHR to cereal rusts and is more susceptible to rusts of the Poaeae than the Triticeae. The active NHR response of Brachypodium to cereal rusts does not prevent sporulation in some instances and shows similarity to basal defense mechanisms active in wheat against adapted cereal rust pathogens. Interestingly an inverse relationship exists between wheat stem and stripe rust resistance in Brachypodium, with those lines allowing more growth of wheat stem rust being more effective at suppressing wheat stripe rust growth and vice versa.