Screening two wild-sourced Australian Myrtaceae for responses to Austropuccinia psidii (myrtle rust) and determining the underlying genetic basis to resistance

Austropuccinia psidii is a biotrophic fungal pathogen, first described in Brazil, and the causal agent of rust infections commonly named myrtle rust. A. psidii was initially detected in Australia in April 2010 in a commercial nursery, and by late that year, had become established on a wide range of species within the Australian Myrtaceae and deemed ineradicable. Currently it is believed that only one genotype of the pathogen is present in Australia, which matches an Hawaiian pathotype, based on molecular markers. Within Australia infection responses vary from complete susceptibility to resistance within a number of distantly related species, within populations and provenances, indicating a large degree of host genetic diversity. While there are concerns for Australian natural vegetation communities, dominated by Myrtaceae, established and emerging commercial species are also likely to be impacted. The following research takes two commercially important Australian Myrtaceae; Chamelaucium uncinatum, grown for the cut flower market and Syzygium luehmannii, an increasingly valuable berry crop, and examines their responses to inoculation with Austropuccinia psidii. Differential gene expression analysis, based on resistant versus susceptible phenotypes, show that responses have an underlying molecular basis