Abstract
Although Phytophthora species cause serious diseases worldwide, until recently the main focus on disease in natural ecosystems in southern Australia has been on the distribution and impact of P. cinnamomi. However, new Phytophthora pathogens have emerged from natural ecosystems, and there is a need to better understand the diversity and distribution of these species in our natural forests, woodlands and heathlands. From a survey along a 70 km pipeline easement in Victoria, Phytophthora species were isolated from 249 rhizosphere samples and 25 bait bags deployed in 21 stream, river, or wetland locations. Of the 186 Phytophthora isolates recovered, 130 were identified to species based on ITS sequence data. Ninety-five isolates corresponded to 13 described Phytophthora species while additionally 35 isolates were identified as Clade 6 hybrids. Phytophthora cinnamomi was the most common species isolated (31 %), followed by P. elongata (6 %), both species were only recovered from soil. Samples from sites with the highest soil moisture at the time of sampling had the highest yield of isolates. Consistent with other studies throughout the world, Clade 6 species and their hybrids dominated water samples, although many of these species were also recovered less frequently from soil samples. Many of the species recovered in this study have not previously been reported from eastern Australia, reinforcing that Phytophthora species are widespread, abundant and diverse in natural ecosystems. We have probably been underestimating Phytophthora diversity in Australia.
Highlights
Phytophthora causes serious diseases worldwide in agriculture, horticulture and natural ecosystems, it is only recently that accurate identi¿cation of many species of these important plant pathogens has been made possible using molecular methods
The soil and water sampling yielded 186 Phytophthora isolates; based on molecular identi¿cation 130 of these isolates corresponded to species and hybrids from Clades 2, and 6–9 (Tables 2–3)
Sixty-four Phytophthora isolates were obtained from the water baits (Table 3), with one to three Phytophthora isolates recovered from each baiting location (Table 2)
Summary
Phytophthora causes serious diseases worldwide in agriculture, horticulture and natural ecosystems, it is only recently that accurate identi¿cation of many species of these important plant pathogens has been made possible using molecular methods. Jung et al (2005) suggest that all Phytophthora species have the potential to cause plant health decline in natural ecosystems, when there are assemblages of different introduced species present, and conditions are conducive for disease development (Scott et al 2013). The impact of P. cinnamomi is greatest in the natural communities of the south-west and south-east of Australia, where it has caused the loss of animal species along with changes in species abundance and population structure (Cahill et al 2008), resulting in changes in Àoristic structure, diversity, and ecological processes (Shearer et al 2004, McDougall et al 2005). McDougall (2005) compiled a list of over 1460 species known to be susceptible, after P. cinnamomi had been isolated from infected plants or found in susceptibility testing.
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