Movement of the devasting Eucalytpus leaf and shoot pathogen Phaeophleospora destructans, throughout Asia

Phaeophleospora destructans was first described in 1996 from north Sumatra, Indonesia, where it causes a severe leaf and shoot blight on Eucalyptus grandis in nurseries and young plantations. Since then it has been reported in nurseries and plantations in Vietnam and Thailand, with its host range extending to include E. camaldulensis and E. urophylla, Phaeophleospora destructans has also been reported from native E. urophylla in East Timor, presenting the possibility it may be native pathogen there. During surveys of nurseries in Southern China in 2004/2005, P. destructans was found to be widespread, including areas where there are no plantations, strongly suggesting that the pathogen is being transported throughout the region on infected germplasm. The ITS, beta-tubulin and elongation factor I-alpha gene regions of three P. destructans isolates from each of Sumatra, Vietnam, Thailand and Southern China were sequenced and found to be identical. Microsatellite markers were developed for p, destructans using the FIASCO (fast isolation by AFLP of sequences containing repeats) enrichment technique and although 7 repeat-rich gene regions were identified, none of them were variable among the representative isolates tested, It appears that P. destructans in nurseries and plantations in Asia has very low genetic diversity. This could suggest a recent host jump from another species onto Eucalyptus or the introduction and movement of a very limited gene pool from Sumatra to the rest of Asia. Phaeophleospora destructans is currently absent from Australia but its devastating nature could potentially impact on biodiversity of native vegetation and productivity of Eucalyptus plantations and is thus considered a major biosecurity threat. The apparently low genetic diversity of the pathogen should reduce the risk of the impact that it could have on native ecosystems if introduced to Australia, butt plantations of susceptible trees would be at risk. A new initiative has recently been launched to test the susceptibility of native Australian eucalypt species to P. destructans