Fire blight is the most devastating disease affecting pome fruit production globally.The pathogen is native to North America and was imported to western Europe in the 1950s,progressively spreading over the continent i...Fire blight is the most devastating disease affecting pome fruit production globally.The pathogen is native to North America and was imported to western Europe in the 1950s,progressively spreading over the continent in the ensuing decades.Previous phylogenetic studies have revealed the extreme genetic homogeneity of the pathogen outside its center of origin,which makes epidemiological studies difficult.These are generally only possible using hypervariable regions of the genome such as those represented by CRISPRs(Clustered Regularly Interspaced Short Palindromic Repeats),which are,however,not practical to sequence due to their size and variability.Here,we present a simple PCR assay targeting the duplication of a single CRISPR spacer in Erwinia amylovora that was found to be an important marker to discriminate between two main European populations of the pathogen.We implemented the assay on a total of 582 isolates to follow the spread of fire blight across the continent over several decades and,wherever possible,within single countries.The results obtained point to the occurrence of two major separate introduction events for E.amylovora in Europe that occurred approximately 20 years apart,and confirmed the existence of two principal distribution areas located in Northeastern Europe and the Eastern Mediterranean Basin from which the pathogen moved on to colonize the Eurasian continent.展开更多
基金Financial support was provided by the Swiss National Science Foundation(SNSF)for the research project“Preservation of Central Asian fruit tree forest ecosystems,pome fruit varieties and germplasm from the recent epidemics caused by the invasive bacterial pathogen Erwinia amylovora(fire blight)”(Project No.IZ08Z0_177515)the European Union FP7 EUPHRESCO ERANet project“Phytosanitary diagnostic,on-site detection and epidemiology tools for Erwinia amylovora(PhytFire)”.
文摘Fire blight is the most devastating disease affecting pome fruit production globally.The pathogen is native to North America and was imported to western Europe in the 1950s,progressively spreading over the continent in the ensuing decades.Previous phylogenetic studies have revealed the extreme genetic homogeneity of the pathogen outside its center of origin,which makes epidemiological studies difficult.These are generally only possible using hypervariable regions of the genome such as those represented by CRISPRs(Clustered Regularly Interspaced Short Palindromic Repeats),which are,however,not practical to sequence due to their size and variability.Here,we present a simple PCR assay targeting the duplication of a single CRISPR spacer in Erwinia amylovora that was found to be an important marker to discriminate between two main European populations of the pathogen.We implemented the assay on a total of 582 isolates to follow the spread of fire blight across the continent over several decades and,wherever possible,within single countries.The results obtained point to the occurrence of two major separate introduction events for E.amylovora in Europe that occurred approximately 20 years apart,and confirmed the existence of two principal distribution areas located in Northeastern Europe and the Eastern Mediterranean Basin from which the pathogen moved on to colonize the Eurasian continent.
