Diverse strains of aster yellows phytoplasma are associated with the potato leafhopper (Empoasca fabae) in Eastern Canada.

Phytoplasmas are cell wall-less bacteria that are transmitted by phloem-feeding insects. In Canada, insect vectors of this pathogen are leafhoppers (Hemiptera: Cicadellidae), and they can contribute to significant economic losses. As climate change alters the composition and movement of insect communities, migratory species such as the potato leafhopper (Empoasca fabae, Harris 1841), one of the most abundant leafhoppers in Québec affecting berries, may play an emerging role in phytoplasma transmission. Although E. fabae is not currently confirmed to act as a vector, its frequent presence and abundance in fields, along with its potential to acquire phytoplasmas, deserve further investigation. In this study, we tested DNA from E. fabae collected in strawberry fields for the presence of 'Candidatus Phytoplasma' using a highly validated nested PCR assay. The amplicon from positive insects were cloned and 46 of those clones were sequenced to identify phytoplasma groups and subgroups. Our findings confirmed the presence of multiple Aster Yellows (16SrI-related) subgroups in E. fabae, based on phylogenetic analysis, restriction fragment length polymorphism (RFLP) profiling, and single-nucleotide polymorphism (SNP) profiles. However, although phytoplasma was detected in a new generation of leafhoppers reared under controlled conditions in disease-free alfalfa plants, the ability of E. fabae to transmit the pathogen remains unknown. Overall, these findings highlight the importance of monitoring common pests such as E. fabae as early indicators of phytoplasma diversity in Eastern Canadian agricultural systems.