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Diaporthe species identified from woody plants close to vineyards in South Africa

Francois Halleen: Agricultural Research Council

<div>Many <em>Diaporthe</em> species are known to have broad host ranges, and different species can occur on the same host. In South Africa, <em>D. ampelina </em>is considered a major grapevine pathogen, however, several other <em>Diaporthe </em>species have also been associated with grapevine diseases. These include <em>D. amygdali</em>, <em>D. helianthi</em>, <em>D. cynaroidis</em>,<em> D. novem </em>and<em> D. serafiniae </em>that are also known from other hosts. These findings have led to an investigation of <em>Diaporthe </em>species associated with woody plants in close proximity to grapevines to assess the risk these plants pose as potential inoculum sources of grapevine pathogens. Isolations were made from 25 different species of woody plants near grapevines in the Western Cape Province. Cultures identified as <em>Diaporthe </em>based on cultural and morphological features were identified to species level by sequencing the internal transcribed spacer region (ITS) and, for representative isolates, the beta-tubulin (TUB2) region. Phylogenetic analysis of the combined ITS and TUB2 data revealed 16<em> Diaporthe </em>species associated with the 25 woody hosts. Seven of these <em>Diaporthe </em>species have been reported as possible pathogens of grapevines in South Africa. These findings suggest possible inoculum movement of several <em>Diaporthe</em> species between grapevines and other woody plants. <em>Diaporthe ampelina </em>was not recovered from non-grapevine hosts, confirming previous suggestions that this species is host-specific.</div>