New species of Phytophthora
In recent studies, the following new species of Phytophthora have been described.
- Phytophthora austrocedrae isolated from Austrocedrus chilensis in Argentina
In Argentina, widespread mortality has been observed for many years in Patagonia on trees of Austrocedrus chilensis (Cupressaceae – Cordilleran cypress) but its etiology remained unclear. The disease (called ‘mal del cipres’ or ‘secamiento del cipres’) was first noticed in 1984 on Victoria Island (Nahuel Haupi National Park). It was then observed throughout the natural range of A. chilensis in forests (Andean foothills) and also in cities where it was planted for ornamental purposes. The disease was more particularly present in poorly drained areas (Filip and Rossa, 1999). In recent studies, a new Phytophthora species, called Phytophthora austrocedrae sp. nov. could be isolated from necrotic lesions on stems and roots of A. chilensis affected by the disease. Although pathogenicity tests to fulfil Koch’s postulates are still under way, evidence gathered suggested that P. austrocedrae is the primary cause of the disease. Further studies will be made to better understand the geographical distribution of P. austrocedrae in Argentina and better characterize the associated symptomatology (Greslebin et al., 2007).
- Phytophthora frigida and P. alticola isolated from eucalyptus in South Africa
Studies were carried out in South Africa to determine the cause of collar and root rots which are currently being observed in plantations of cold-tolerant eucalyptus species. Several Phytophthora species (i.e. P. boehmeriae, P. cinnamomi and P. nicotianae) are known to be associated with collar and root rot of eucalyptus in South Africa, but it was still unclear if other species (possibly invasive) were also involved. As a result of these studies, two new Phytophthora species could be isolated from diseased eucalyptus and were called Phytophthora frigida sp. nov. and Phytophthora alticola sp. nov. Pathogenicity tests carried out in the field on Eucalyptus dunnii, showed that they were less pathogenic than P. cinnamomi (Maseko et al., 2007).
- Phytophthora quercetorum isolated from oak forest soils in the USA
In the USA, a survey was conducted in 2004 and 2005 in oak forests to determine Phytophthora species present. Seven species were detected, of which three appeared to be undescribed taxa. The second most common species isolated during the survey was described and called Phytophthora quercetorum sp. nov. This new species was isolated from rhizosphere soils collected around the base of mature oak trees in 6 US states (Maryland, Minnesota, Ohio, Pennsylvania, Wisconsin, West Virginia). It is not known whether this new Phytophthora species can cause diseases on oak trees. However preliminary pathogenicity tests suggest that it has the potential to affect the root system and thus may play a role in oak decline (Balci et al., 2008).
Balci Y, Balci S, Blair J, Park SY, Kang S, Macdonald WL (2008) Phytophthora quercetorum sp. nov., a novel species isolated from eastern and north-central USA oak forest soils. Mycological Research 112(8) 906-916.
Filip GM, Rosso PH (1999) Cypress mortality (mal del cipres) in the Patagonian Andes: comparisons with similar forest diseases and declines in North America. European Journal of Forest Pathology 29(2), 89-96.
Greslebin AG, Hansen EM, Sutton W (2007) Phytophthora austrocedrae sp. nov., a new species associated with Austrocedrus chilensis mortality in Patagonia (Argentina). Mycological Research 111(3), 308-316.
Maseko B, Burgess TI, Continho TA, Wingfield MJ (2007) Two new Phytophthora species from South African Eucalyptus plantations. Mycological Research 111(11), 1321-1338.