DNA barcoding of Australian cereal cyst nematode populations with comments on likely origin and taxonomy (Tylenchoidea: Heterodera)

Abstract

A species of Heterodera has been known to parasitise cereals in Australia since the 1930s. It caused significant yield losses across Australia’s cereal growing regions until resistance breeding largely brought it under control, although it still occurs occasionally, especially in South and Western Australia. Australian cereal cyst nematode has long been considered to represent Heterodera avenae. However, in 2002 the name Heterodera australis was proposed for Australian cereal cyst nematode, as it could be distinguished from all non-Australian populations of H. avenae via biochemical and molecular methods. This new species proposal came 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 barcoding approach (COI, 18S, ITS, 28S) we examined the species composition of 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. We also argue that, based on presently available evidence, H. australis is not native and was most likely introduced into Australia from Asia in the 1850s, rather than from Europe as has been generally assumed.