02274nas a2200217 4500008004100000022001300041245012800054210006900182260001600251300001400267490000800281520155000289100001901839700002401858700002201882700002701904700002601931700002701957700002301984856004902007 2013 eng d a1878614600aCharacterization of Phytophthora hybrids from ITS clade 6 associated with riparian ecosystems in South Africa and Australia0 aCharacterization of Phytophthora hybrids from ITS clade 6 associ cJan-05-2013 a329 - 3470 v1173 a

Surveys of Australian and South African rivers revealed numerous Phytophthora isolates residing in clade 6 of the genus, with internal transcribed spacer (ITS) gene regions that were either highly polymorphic or unsequenceable. These isolates were suspected to be hybrids. Three nuclear loci, the ITS region, two single copy loci (antisilencing factor (ASF) and G protein alpha subunit (GPA)), and one mitochondrial locus (cytochrome oxidase c subunit I (coxI)) were amplified and sequenced to test this hypothesis. Abundant recombination within the ITS region was observed. This, combined with phylogenetic comparisons of the other three loci, confirmed the presence of four different hybrid types involving the three described parent species Phytophthora amnicola, Phytophthora thermophila, and Phytophthora taxon PgChlamydo. In all cases, only a single coxI allele was detected, suggesting that hybrids arose from sexual recombination. All the hybrid isolates were sterile in culture and all their physiological traits tended to resemble those of the maternal parents. Nothing is known regarding their host range or pathogenicity. Nonetheless, as several isolates from Western Australia were obtained from the rhizosphere soil of dying plants, they should be regarded as potential threats to plant health. The frequent occurrence of the hybrids and their parent species in Australia strongly suggests an Australian origin and a subsequent introduction into South Africa.

1 aNagel, Jan, H.1 aGryzenhout, Marieka1 aSlippers, Bernard1 aWingfield, Michael, J.1 aHardy, Giles, E.St.J.1 aStukely, Michael, J.C.1 aBurgess, Treena, I uhttps://doi.org/10.1016/j.funbio.2013.03.004