Two new Phytophthora species from South African Eucalyptus plantations

Abstract

A recent study to determine the cause of collar and root rot disease outbreaks of cold tolerant Eucalyptus species in South Africa resulted in the isolation of two putative new Phytophthora species. Based on phylogenetic comparisons using the ITS and β-tubulin gene regions, these species were shown to be distinct from known species. These differences were also supported by robust morphological characteristics. The names, Phytophthora frigida sp. nov. and Phytophthora alticola sp. nov. are thus provided for these taxa, which are phylogenetically closely related to species within the ITS clade 2 (P. citricola, P. tropicali and P.multivesiculata) and 4 (P. arecae and P. megakarya), respectively. Phytophthora frigida is heterothallic, and produces stellate to rosaceous growth patterns on growth medium, corraloid hyphae, sporangia with a variety of distorted shapes and has the ability to grow at low temperatures. Phytophthora alticola is homothallic and has a slower growth rate in culture. Both P. frigida and P. alticola are pathogenic to Eucalyptus dunnii. In pathogenicity tests, they were, however, less pathogenic than P. cinnamomi, which is a well-known pathogen of Eucalyptus in South Africa.

Surveys of soil and water reveal a goldmine of Phytophthora diversity in South African natural ecosystems

“…Phytophthora frigida was first recovered from diseased roots or the rhizosphere of dying Eucalyptus in South Africa (Maseko et al 2007). This species was not highly pathogenic to Eucalyptus when compared to P. cinnamomi , a known and serious root pathogen of Eucalyptus in South Africa (Linde et al 1994).…”

“…have been recovered from plantations of non-native species, mainly located in KwaZulu-Natal, Eastern and Western Cape, and Mpumalanga. These include P. boehmeriae, P. cinnamomi , P. cryptogea , P. nicotianae , P. meadii, P. frigida , and P. alticola (Zeijlemaker 1971, Bumbieris 1976, Wingfield & Knox-Davies 1980, Linde et al 1994, Roux & Wingfield 1997, Maseko et al 2001, Maseko et al . 2007).…”

Phytophthora in the Gondwana Rainforests of Australia World Heritage Area

“…Phytophthora macrochlamydospora appears to be endemic to the north coast of NSW where it has been associated with soybean diseases (Stovold et al 1996;Irwin 1991). To our knowledge, this is the first report of P. frigida in Australia, a species previously recorded in plantation forests in South Africa and Swaziland from Acacia decurrens Willd, A. mernsii, Eucalyptus dunnii Maiden and E. smithii (Maseko et al 2007). Phytophthora frigida has been reported as less pathogenic than P. cinnamomi on E. dunnii in South Africa (Maseko et al 2007).…”

A diverse range of Phytophthora species are associated with dying urban trees

“…growing within plantation forests (Maseko et al, 2007). It was shown to be pathogenic to young E. dunnii growing in the field, and was believed to be a causal agent of dieback and early death of cold-tolerant Eucalyptus species in South Africa.…”