An international scientific team led by Thomas Jung has discovered and described more than forty previously unknown species of pathogens from the genus Phytophthora which parasitize the root systems of trees. These findings are the results of a six-year project by the Phytophthora Research Centre at FFWT MENDELU. The previously unknown species were found in south-eastern Europe, south-eastern and eastern Asia, and South America. They originated primarily from natural ecosystems, but also partially from forest nurseries and planted forests. The study has significantly contributed to the understanding of tree pathogen diversity. The results will be utilized by institutions involved in plant protection and monitoring harmful organisms.
Phytophthora, also known as water moulds from the genus Phytophthora, are soil microorganisms that are very difficult to identify: “Unlike fungi, they do not produce fruiting bodies, so they are not conspicuous. We only recognize that a tree has been attacked by a Phytophthora on the basis of the tree’s condition. An infected tree dries out and unusual necroses form on the trunk,” explained Michal Tomšovský, one of the study’s co-authors, describing the problematic pathogens.
Dormant spores pose a significant risk to tree health. They can survive long-term in the soil, waiting for their opportunity: “Originally, they are soil and water organisms, so they thrive in heavy rain or flooding as they prefer wet conditions. Run-off allows the further spread of spores in waterlogged soil, and waterlogged trees are additionally stressed, their roots suffocate due to a lack of air, providing further opportunity for parasite attack,” said Tomšovský, describing the ideal conditions for the spread of Phytophthora mould.
The pathogens are identified from the soil and infected trees using a molecular biological method known as DNA sequencing: “This sequencing is similar to the system known to the public from the Covid-19 pandemic. DNA sequencing is important when there is suspicion of a serious pathogen. It is an accurate method where scientists or plant doctors can relatively quickly determine the cause of damage to trees. However, the problem lies with plant material from exotic countries where the biodiversity of these organisms is not well known. Sequencing results then reveal sequences which experts cannot classify and do not know what to expect from the captured organisms. This is why studies of this type are so important,” Tomšovský emphasized the study’s significance.
The authors of the study see a risk in the inadequately controlled import of potentially contaminated material, which can spread in public greenery and private gardens. Plant health legislation focuses only on controlling a few quarantine harmful organisms, and Phytophthora pathogens are practically not among them: “A fundamental problem is the import of planting material into Europe from other continents. Organisms that are not native arrive here and can cause significant damage to the root systems of native trees. We have already recorded such cases in Central Europe,” the scientist explained.
During the research, scientists conducted expeditions to third countries and analysed several hundred soil isolates. Each obtained Phytophthora isolate was subjected to DNA sequencing, and if it was a species previously unknown to science, it was thoroughly examined under a microscope and described as a new species.
The discovery of more than forty new species of the genus Phytophthora is considered by scientists as evidence of how little is known about these pathogens causing severe plant diseases. Therefore, they consider further research of natural ecosystems in unexplored areas of the world essential.
The study, which provides valuable findings for pathogen detection, will be utilized by the professional plant health community, especially by the Central Institute for Supervising and Testing in Agriculture in the Czech Republic.
The study results were published in the prestigious scientific journal Studies in Mycology.
Contact for further information: Prof. RNDr. Michal Tomšovský, Ph.D., Department of Forest Conservation and Wildlife Management, FFWT MENDELU, +420 545 134 115, michal.tomsovsky@mendelu.cz