First record of Cryptosporiopsis actinidiae in Australia

In 1986 a large number of fungal isolations were made from rot and discolouration in karri trees (Eucalyptus diversicolor) from regrowth stands in the south-west of Western Australia (Davison and Tay 2008). This was part of a study to determine which fungi caused these symptoms and whether all symptoms of discolouration would ultimately develop into rot. Many different symptoms were sampled including a dark discolouration associated with galleries of larvae of the common wood boring beetle Phoracantha acanthocera. One mitosporic fungus (DCE 312) obtained from this symptom in freshly sawn scantling was used in subsequent experiments. It was sent to the Commonwealth Mycological Institute and was identified as Colletotrichum acutatum. This isolate caused a brown discolouration when grown on tannic acid agar, indicating that it produced extracellular oxidases (Nobles 1965). When inoculated into the sapwood and heartwood of regrowth karri trees it persisted in some inoculations for up to 4 years, and caused a dark discolouration in the sapwood.

The identity of DCE 312 was checked in 2006 as part of an attempt to identify some of the cultures isolated from rot and discoloured wood. The rDNA (rDNA) internal transcribed spacer (ITS) region was amplified and sequenced using primers ITS5 and ITS4 (White et al. 1990). BLAST searches revealed this sequence to be identical or up to four bases different to the Cryptosporiopsis actinidiae ITS sequences on GenBank.

Cryptosporiopsis actinidiae was described from New Zealand by Johnston et al. (2004). It causes an economically important post-harvest rot of yellow-fleshed kiwifruit (Actinidia chinensis var. chinensis ‘Hort16A’) (Fullerton et al. 2007; Wurms et al. 2007) but has a wider host range including other species of kiwifruit (A. arguta, A. deliciosa and A. indochinensis), apple (Malus × domesticus) and persimmon (Diospyros virginiana). It has also been isolated at low levels from native forest in New Zealand (Johnson et al. 2005). Genetic analysis of isolates from several different locations and hosts has shown that it is outbreeding with five vegetative compatibility genes; the teleomorph is likely to be a Neofabraea sp., but has not been identified (Beever and Parkes 2007).

The morphology and cultural characteristics of isolate DCE 312 agree with the original description of C. actinidiae (Johnston et al. 2004). In particular, this isolate was a characteristic intense red on the reverse when grown on potato dextrose agar. The conidia were hyaline, smooth, cylindrical, rounded at the apex, tapered at the base with a truncate scar, [20/1] (5−) 7.5–13.5 (−15) × 1.5–3 µm (Fig. 1). The only discrepancy was that the conidia in the original description were wider, ranging from 3–5.5 µm. To our knowledge this is the first report of C. actinidiae in Australia.

Fig. 1.  Conidia and conidiogenous cells of Cryptosporiopsis actinidiae (DCE 312). Scale bar = 10 µm.

Cultures of C. actinidiae (DCE 312) have been deposited at the Department of Agriculture and Food Western Australia as WAC 13024, and at the International Mycological Institute, UK, as IMI 316717. The rDNA ITS sequence has been deposited on GenBank as accession FJ974105.