High-Throughput Sequencing to Investigate Phytopathogenic Fungal Propagules Caught in Baited Insect Traps

Abstract

Studying the means of dispersal of plant pathogens is crucial to better understand the dynamic interactions involved in plant infections. On one hand, entomologists rely mostly on both traditional molecular methods and morphological characteristics, to identify pests. On the other hand, high-throughput sequencing (HTS) is becoming the go-to avenue for scientists studying phytopathogens. These organisms sometimes infect plants, together with insects. Considering the growing number of exotic insect introductions in Canada, forest pest-management efforts would benefit from the development of a high-throughput strategy to investigate the phytopathogenic fungal and oomycete species interacting with wood-boring insects. We recycled formerly discarded preservative fluids from the Canadian Food Inspection Agency annual survey using insect traps and analysed more than one hundred samples originating from across Canada. Using the Ion Torrent Personal Genome Machine (PGM) HTS technology and fusion primers, we performed metabarcoding to screen unwanted fungi and oomycetes species, including Phytophthora spp. Community profiling was conducted on the four different wood-boring, insect-attracting semiochemicals; although the preservative (contained ethanol) also attracted other insects. Phytopathogenic fungi (e.g., Leptographium spp. and Meria laricis in the pine sawyer semiochemical) and oomycetes (mainly Peronospora spp. and Pythium aff. hypogynum in the General Longhorn semiochemical), solely associated with one of the four types of semiochemicals, were detected. This project demonstrated that the insect traps’ semiochemical microbiome represents a new and powerful matrix for screening phytopathogens. Compared to traditional diagnostic techniques, the fluids allowed for a faster and higher throughput assessment of the biodiversity contained within. Additionally, minimal modifications to this approach would allow it to be used in other phytopathology fields.

Cryptic Risks to Forest Biosecurity Associated with the Global Movement of Commercial Seed

“…Despite the growing body of evidence for its usefulness in the early detection and surveillance of potentially invasive forest pathogens [27][28][29], and its high sensitivity and capacity to deal with large numbers of samples in less time compared to traditional methods [30], HTS is generally underutilized as a tool in plant biosecurity [31][32][33][34][35].…”

New qPCR protocol to detect Diplodia corticola shows phoretic association with the oak pinhole borer Platypus cylindrus

“…The estimated spore load did not show any temporal cumulative trend caused by contamination by D. corticolaś spores, despite the fact that insect traps could act as passive spore collectors. 30,31 Temporal pattern described here suggests irregular spore production and/or vegetative growth during the summer with an intriguing lack of propagules in autumn (September onwards), even though mean temperature remained approximately 20 °C and humidity reached 75% in the sampled plots. The apparent absence of inoculum in autumn contrasts with the expected sporulation phenology since other Diplodia spp.…”

Meta-Analysis and Evaluation by Insect-Mediated Baiting Reveal Different Patterns of Hypocrealean Entomopathogenic Fungi in the Soils From Two Regions of China

“…We should mention that the species-level assignment (Figure 4) must be interpreted with some caution because using ITS2 for soil-fungal entomopathogen composition structures does not provide informative molecular delimitation below the genus level accurately, especially for the closely related species in some genera such as Metarhizium and Beauveria, and that is a straightforward consequence of the dependence of culture-independent metabarcoding approach on databases. For this reason, proper identification should be integrated with additional standard techniques (Tremblay et al, 2019). In this study, Metarhizium and Beuaveria were relatively abundant across all sampling sites.…”