Tracing introduction pathways, genetic diversity, and adaptive strategies of Erwinia amylovora in Portugal agroecosystems for improved disease management

Erwinia amylovora, the etiological agent of fire blight disease, is an important threat to pome fruit production worldwide, particularly affecting apple (Malus domestica) and pear (Pyrus communis) trees and a wide number of other hosts within the Rosaceae family. When entering the cells, the bacteria disrupt the plant’s natural defense mechanisms and, once inside the xylem, can form biofilms, leading to tissue death due to blocked water and essential minerals transport. Unfortunately, there are no effective methods to halt the spread of this disease, which is aggravated by environmental changes that create favorable climatic conditions and the increased international trade of contaminated plant material. Despite its global prevalence and ability to infect a plethora of ornamental and edible hosts, studies indicate a high level of genomic homogeneity among E. amylovora strains worldwide. Despite previous genomic characterization efforts in Portugal, the lack of comprehensive epidemiological data and understanding of local environmental influences on pathogen evolution prevents effective management and outbreak prediction. In this study, results from phylogenetic inference and CRISPR CRR1 identification raise the hypothesis that there are at least two different invasion routes for E. amylovora in Portugal, or that different dissemination routes occurred since the first entry in the country. Phenotypic data are being collected on 82 Portuguese isolates, which already disclosed strains with growth rates ranging from 0.155 to 0.315 h-1 and different virulence levels. This metadata will be integrated with genomic analysis such as the identification of single-nucleotide polymorphisms (SNPs); functional annotation of candidate genes like ams, rls, and hrp; and exploration of relevant plasmid presence to elucidate the phenotypic variability among isolates. The findings will address gaps in understanding E. amylovora’s genome regulation to shed light on the evolutionary mechanisms driving fire blight’s adaptation and success, ultimately contributing to outbreak mitigation and improving disease management.

This work received financial support from PT national funds (FCT/MECI, Fundação para a Ciência e Tecnologia and Ministério da Educação, Ciência e Inovação) through the projects UID/50006 -Laboratório Associado para a Química Verde - Tecnologias e Processos Limpos and 2023.01413.BD.