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The BSPP travel fund helped me attend Plant Health 2019, the annual meeting of the American Phytopathological Society (APS). The meeting lasted 5 days and there were almost 1,300 attendees, including students, academics and industry, from the USA and over 40 countries globally.
My experience kicked off with a field trip to woodland areas around the Great Lakes Region to learn about existing and emerging forest health challenges. The emerging Beech Leaf Disease (BLD) is a matter of increasing concern in the North East USA. BLD was first observed in Ohio in 2012 and has now spread across Pennsylvania, New York and Ontario. The disease affects American beech (Fagus grandifolia), European beech (F. sylvatica) and Oriental beech (F. orientalis). Symptoms manifest as dark banding between lateral veins of leaves (pictured on the front cover).
Subsequently, leaves become thick, leathery in texture and the edges tend to curl. Buds fail to produce new leaves and as a result canopy is increasingly reduced over time. Saplings particularly can die within 2-5 years. Much about this disease remains unclear. The causal agent has not been officially confirmed, despite evidence suggesting an association with a foliar nematode (Litylenchus crenatae). There may be a vector involved due to its very fast rate of spread.
A keynote talk I enjoyed was presented by Prof William A. Powell from State University of New York. He illustrated the use of genetic engineering to confer American chestnut tree (Castanea dentata) resistance to chestnut blight (Cryphonectria parasitica). His group produced resistant trees using the oxalate oxidase (OxO) gene from Triticum aestivum, which is widespread in the environment as well as in our food. By acting as an antitoxin rather than a fungicide, the gene is considered less likely to lead to the development of resistant pathogen strains. Their transgenic chestnut line is currently being submitted to the USDA.
Another interesting presentation was given by Professor Paul Cobine from Auburn University, regarding the xylem ionome, a “snapshot” of the mineral content of xylem sap. Both plants and pathogens require an optimal concentration of essential metal ions for their survival, and this translates into a tug of- war between the host and vascular pathogen to secure the available ions in the sap. Indeed, the xylem ionome of infected plants has been shown to correlate with symptom severity, while Professor Cobine and colleagues also showed that there is a difference between the ionomes of olive cultivars which differ in their susceptibility to Xylella fastidiosa.
The technical session “Advanced detection and diagnosis of plant diseases”= was very useful, as it provided updates on the most recent developments in pathogen detection technologies. Two presentations by scientists at the North Carolina State University introduced smart and cost-effective technologies for the diagnosis of tomato late blight caused by Phytophthora infestans. Professor Qingshang Wei described a field portable, smartphone-based volatile organic compound (VOC) sensor platform, combining a chemical sensor and a mobile reader into a device that can profile leaf volatile emissions, allowing non-invasive and early diagnosis of infections. Rajesh Paul presented instead a very fast DNA extraction technique based on polymeric microneedles that allowed isolation of leaf DNA in less than a minute.
I also enjoyed all the sessions on the plant and soil associated microbiomes.
My PhD work involves a meta-barcoding study of apple endophytes, and these talks provided useful demonstrations of how to approach the analysis and interpretation of my data. Krystel Navarro from Ohio State University discussed a meta-barcoding study investigating soil factors affecting Pythium and Phytophthora population dynamics. She showed how agricultural practices such as crop rotation contribute to shaping oomycete pathogens communities in soil. Professor Joanne Emerson (University of California, Davis) presented the results of meta-genomic analyses of the viral communities in different matrices, which unravelled an unexpected diversity and abundance of viral communities in soil and plant.
I would like to thank the BSPP for providing funds supporting my travel.
Plant Health 2019 represented an invaluable opportunity for professional network building, meeting academics and industry representatives, and exploring collaboration and career opportunities.
I also gave a talk on my PhD work focussed on the biology and microbial ecology of the pathogenic fungus Neonectria ditissima, causal agent of apple canker, which greatly helped increasing my professional visibility. I definitely recommend for all PhD candidates out there to attend and present at Plant Health 2020 in Denver, Colorado!
Leone Olivieri NIAB EMR and Royal Holloway, University of London The theme of the meeting was ‘Sow, Know, and Grow’. I was first struck by the size of the conference and the presence of plant pathologists from all over the world. More than 40 special and technical sessions and nearly 700 posters were elaborated to cover most of research areas in plant pathology. Dr Jude Wilson opened the meeting with the talk ‘The Surprise Science of Mushrooms’, highlighting her journey in science, now focused on mushrooms.
With such a diverse range of topics it was rather difficult to choose which session to attend. As a PhD student I tended to focus on my own project, and soon found myself attending the special session “The promise and limitations of SDHI fungicides”. Gerd Stammler (BASF SE) gave a talk on the status of SDHI resistance development. Target site mutations have been found in encoding genes of three subunits of succinate hydrogenase (SdhB, C and D) conferring fungicide insensitivity in various fungal species. Some of these mutations cause loss of sensitivity to all SDHI fungicides, while other mutations do not confer complete cross resistance.
Concerning Zymoseptoria tritici, most of the isolates found in Europe have wild type Sdh genes. Isolates carrying the CH152R mutation have the highest resistance factor for SDHI fungicides. Double mutations are rarely found and enhanced efflux pump phenotypes (Multi Drug Resistance -MDR) have limited responses on SDHI sensitivity. More recently, a second SdhC paralog has been detected in some strains; resulting in a loss of sensitivity to a subclass of SDHI fungicides. Anne-Sophie Walker (INRA Bioger) presented ‘Assessing the risk of resistance towards SDHI fungicides in France’, where resistance has already emerged in nine fungal species. In Z. tritici, increased efflux pump activity led to low levels of fungicide resistance, while target site mutations are associated with low to high resistance factors; although not reported in France both mechanisms have been found combined in some UK field isolates. Laboratory crosses of French strains resulted in progenies harbouring the two mechanisms with high resistance factors and low fitness penalties. Finally, Guido Schnabel (Clemson University) talked about the use of SDHI fungicides in pre-mixtures.
Although this strategy has showed to be promising for delaying the emergence of fungicide resistance in some crops, the use of SDHI/QoI premixtures for gray mold (Botrytis cinerea) control in strawberry plantations may have selected for QoI resistance of anthracnose (Colletotrichum acucatum).
The conference also hosted a special session on ‘Impacts of agricultural fungicides on clinical anti-fungal resistance’. Bart Fraaije (Rothamsted Research) opened the session talking about the use of azoles to control cereal diseases and the emergence of resistance in Aspergillus fumigatus. These fungicides have been used since the late 1970s in Broadbalk, the Rothamsted long-term winter wheat field experiment.
Few highly resistant strains of A. fumigatus where isolated from soil sampled in treated but also in untreated plots, as well as from air sampled from the environment, ruling out cereal fields as a hotspot for emergence of azole resistant strains. Karlyn Beer (CDC National Center for Emerging and Zoonotic Infectious Diseases) debated mortality caused by A. fumigatus in high-risk patients and how it increases with azole resistance strains being reported worldwide, mostly associated with environmental fungicide usage. Martin Brewer (University of Georgia) genotyped azole resistant and sensitive strains of A. fumigatus from both agriculture and clinical environment. No genetic clustering was found for agricultural isolates, but an azole resistant lineage could be observed.
Martin Semar (FRAC) closed the session concluding that broad-acre crop environment is unlikely to be a hotspot for azole resistance emergence of A.fumigatus strains, but some agricultural practices such as composting crop residues treated with azoles are most likely a hotspot. Because this topic has been widely discussed on the media, it was debated again in a panel discussion with experts from governmental organisations and in a roundtable conversation where professionals researching fungicide resistance could chat about new techniques, exchange ideas and set collaborations.
I also had the opportunity to finally meet collaborators, from Oregon State University and Michigan State University, responsible for collecting North American Z. tritici samples that I am studying in my PhD research. The conference concluded on a pleasant dinner at the amusing Rock & Roll Hall of Fame followed by dance on the nostalgia of rock ‘n’ roll legends. To finish, I would like to thank the BSSP for the travel award that enabled me to attend this very important conference. It provided me the opportunity to present my research to a broad audience during poster sessions (see picture above) and I was able to make many new contacts that can potentially benefit my career.
Guilherme Rossato Augusti Rothamsted Research