Australian cereal cyst nematode (Heterodera australis): taxonomic woes and biosecurity implications.

Daniel C. Huston (Australian National Insect Collection, CSIRO); Manda Khudir (Australian National Insect Collection, CSIRO); John Lewis (South Australian Research and Development Institute, South Australia); Sarah Collins (Department of Primary Industries and Regional Development, Western Australia); Akshita Jain (Department of Energy, Environment and Climate Action, Victoria); Mike Hodda (Australian National Insect Collection, CSIRO).

A species of cyst nematode of the genus Heterodera has been known to parasitise cereals in Australia since the 1930s. It caused significant yield losses across Australia until resistance breeding brought it largely under control. Australian cereal cyst nematode has long been considered to represent Heterodera avenae. However, in 2002 the name Heterodera australis was proposed for this nematode, along with speculation that both H. avenae and H. australis might occur in Australia, and that H. australis might represent a native species. The name H. australis has generally not been accepted by Australian scientists, nor the notion that it is native. There remains some uncertainty as to the validity of H. australis and whether more than one species of cereal cyst nematode occur in Australia. Using a molecular approach, we examined cyst nematodes present in soil samples collected between 1989–2023 from Australian cereal growing regions. We find only one species of Heterodera parasitising cereals and, based on phylogenetic analyses, accept the validity of H. australis as the name best representative of this species. Most official biosecurity policy related to this nematode still used the name H. avenae, and the biosecurity implications of this are briefly discussed.