7.02.03 - Vascular wilt diseases
Hot off the press: Hybridization and introgression drive genome evolution of Dutch elm disease pathogens
Pauline Hessenauer, Anna Fijarczyk, Hélène Martin, Julien Prunier, Guillaume Charron, Jérôme Chapuis, Louis Bernier, Philippe Tanguay, Richard C. Hamelin & Christian R. Landry
Nature Ecology & Evolution (2020)
Hybridization and the resulting introgression can drive the success of invasive species via the rapid acquisition of adaptive traits. The Dutch elm disease pandemics in the past 100 years were caused by three fungal lineages with permeable reproductive barriers: Ophiostoma ulmi, Ophiostoma novo-ulmi subspecies novo-ulmi and Ophiostoma novo-ulmi subspecies americana. Using whole-genome sequences and growth phenotyping of a worldwide collection of isolates, we show that introgression has been the main driver of genomic diversity and that it impacted fitness-related traits. Introgressions contain genes involved in host–pathogen interactions and reproduction. Introgressed isolates have enhanced growth rate at high temperature and produce different necrosis sizes on an in vivo model for pathogenicity. In addition, lineages diverge in many pathogenicity-associated genes and exhibit differential mycelial growth in the presence of a proxy of a host defence compound, implying an important role of host trees in the molecular and functional differentiation of these pathogens.
The aim of this Working Party is to promote international collaboration and increased contact among forest pathologists working on wilt diseases of forest trees. The working party has been inactive for several years, however, there is an increasing need to revive interest in this working group. Meetings of the Working Party are scheduled to take place at intervals between 2-4 years. Our wish is to create a relaxed atmosphere among colleagues working on these themes across the world in order to build up a strong group in which ideas could flow freely and where both young and senior researchers are motivated to take part.
State of Knowledge
Reports of new vascular wilt diseases of forest trees causing severe impact glogally have been increasing in recent years. Dutch elm disease, after more than 100 years from its first report, is still a serious problem in many natural woods and urban contexts but there are also emerging vascular wilt diseases such as rapid 'Ōhi'a death caused by two newly described Ceratocystis species in Hawaii. Laurel wilt and plane tree canker stain disease are spreading, threatening their hosts' natural ranges. Bacterial wilts of forest trees, are still an underestimated problem, e.g. Ralstonia solanacearum s.l. causing wilt in Eucalypts. Knowledge exchange and share of experiences are strongly needed to effectively contrast these pathogens at global level.