Rapid and cost‐effective detection of Fusarium euwallaceae from woody tissues

Abstract

The polyphagous shot hole borer (PSHB) Euwallacea fornicatus is an ambrosia beetle that poses a serious threat to hundreds of tree species in invaded countries. In its invaded range, it relies on a mutualistic fungus, Fusarium euwallaceae, for colony establishment and nutrition. Together, the beetle–fungus complex can cause Fusarium dieback disease that can lead to the death of highly susceptible hosts. The key to mitigation of the spread and control of PSHB is its rapid detection. Current identification relies on DNA extraction and sequencing of barcoding genes of the beetle and/or the fungus, which is expensive and time‐consuming. Often the beetle is not present in a sample, and isolation and purification of the fungus is needed before employing molecular procedures. Because PSHB has a strong association with its fungal symbiont, at least in its invaded range, and the fungus can infect trees without successful PSHB colony establishment, a molecular tool that can rapidly detect F. euwallaceae from infected wood would aid monitoring efforts. Here we developed a PCR amplification protocol that targets a species‐specific gene present in F. euwallaceae from within infected wood of various hosts without prior fungal isolation, DNA purification or sequencing. The technique can detect F. euwallaceae within minimal woody material (c.15 mg) and even from degraded samples of many hosts. Additionally, identification of F. euwallaceae using lysate prepared from mycelia provided a reliable secondary measure. This method drastically reduces the time and costs associated with the identification of F. euwallaceae from field samples.

Chromosome structural rearrangements in invasive haplodiploid ambrosia beetles revealed by the genomes ofEuwallacea fornicatusandEuwallacea similis(Coleoptera, Curculionidae, Scolytinae)

“…While the mitochondrial genome for both species have already been published (Guo et al, 2023; Wang et al, 2020), the ability to identify nuclear markers or sequences will be important for the diagnostics and detection (such as through eDNA techniques) of the pests. Diagnostic protocols exist for the detection of E. fornicatus through identification of the symbiont Fusarium euwallaceae (De Jager & Roets, 2022), however, the protocol operates on the detection of fungus in host plant woody tissues, which indicates that the species is already present and likely reproducing in a given locality. Using eDNA techniques and these reference genomes, these pests could be detected early, increasing the chances of eradication or containment, and reducing the time and resources necessary to achieve this.…”