b'Amplicon sequencing revealed significant differences in the diversity of micro-biota, as well as a large number of pathogenic speciesfungi, oomycetes and nematodesthat impact potatoes and other crops. They also found communities of beneficial fungi that act as antagonists to pathogenic fungi, nematodes and in-sects. More research is needed to better understand the interrelationships between all of these soil communities.The Western Committee on Plant Diseases, part of the Western Forum on Pest Management, reported the incidence of PED was higher than normal in 2018, and continued to be an endemic issue in many fields. Fouad Daayf, a University of Manitoba researcher and head of the Plant Sciences Department, admits its hard to tell how widespread the pathogen is since surveys have not been done consistently, and sometimes its not easily distinguished by non-specialist scouters from other issues like Fusarium. For the past 20 years, Daayf has had access to a Natural Sciences and Engi-neering Research Council of Canada Discovery Grant, much of which he has spent on research on potato defence mechanisms against V. dahliae and Phytophthora infestans (late blight), as well as these pathogens counter-defence strategies. Hes also looked at the pathogens genetic diversity. More recently, he has been focusing mainly on the molecular and biochemical basis of Verticillium pathogen-esis in potato.Daayfs team discovered the most aggressive strains of V. dahliae activate genes and produce proteins that interfere with the potatos defensive system. That tells us that it is more complicated than we actually thought, he says. The pathogen enters through the roots, then moves through the vascular system, in a race against the plants defence reactions.However, its not only that, he says. Now were finding that the pathogen has more sophisticated ways to deal with the plant when it tries to defend itself. It sometimes hijacks the defence system of the plant and that involves hormones the plants actually use to coordinate their own defence. Finally, he is also studying how plants fine-tune their defences in an attempt to understand why certain varieties of potatoand other cropsare more susceptible to the pathogen than others. This information could be used to breed less susceptible potato varieties. Incidence of potatoWhen cut, potatoes quickly develop a natural protective layer. Daayf wantedearly dying complex to know if they could help the plant roots do this in the soil where pathogens try tohas been on the rise in fields across the enter, so the potato could better defend itself. To do this, the scientists overex- country.pressed one of the genes responsible for tuber suberization. Daayf says it workedPHOTO: DAHU CHENin the proof-of-concept phase using Arabidopsis (of the Brassicaceae family) and the study has been published. The results of this concept on potato are also conclusive, but are unpublished as of yet.Daayf is also using beneficial bacteria and plant extracts to induce resistancebeen experimenting with biofumigants. Experiments were conducted in commercial that helps fight infection from Verticillium. Working in collaboration with Mariopotato fields in collaboration with McCain Foods.Tenuta, a professor of applied soil ecology at the University of Manitoba, the team In a 20172018 project cycle, the researchers tested brown mustard. They has also been trying to find biofumigants that help deal with pathogens in the soil.chose brown mustard because it contains high glucosinolate, and because it is In particular, Daayf has looked at local plant extracts, like Canada milk vetch andrelatively cheaper than the brand mustard variety used for biofumigation. Under cruciferous species.enzymatic activity, the glucosinolate is converted into a chemical called isothiocy- Once you impregnate the tuber as a seed in Canada milk vetch solution andanate that suppresses pathogens.you plant it, it gives some level of protection to the plant later against Verticillium,AAFC research scientist Dahu Chen joined the Fredericton Research and said Daayf. That is done through the activation of certain defences in the plant. Development Centre in 2017 and was involved in the biofumigation experiment. He explains the results.BIOFUMIGANTS COULD PROVIDE RELIEFBased on our study, we did see significant reduction of the root lesion Led by the now-retired Bernie Zebarth, researchers at the Fredericton Researchnematode counts and suppression of Verticillium after biofumigation, compared and Development Centre of Agriculture and Agri-Food Canada (AAFC) have alsowith the control, though significant disease severities were not detected among 40 SPUDSMART.COM WINTER 2020'