Page 149 - Plant Canada 2024 Proceeding

PLANT CANADA 2024

[O94] PREVALENCE OF VERTICILLIUM SPP. AND PRATYLENCHUS SPP. IN COMMERCIAL
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POTATO FIELDS IN EASTERN CANADA. Dahu Chen , Ryan Barrett , Benjamin Mimee , Tanya
Arseneault , Louis-Pierre Comeau , Kamrun Nahar , Sebastian Ibarra Jimenez , and Bernie J. Zebarth .
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1 Fredericton Research and Development Centre, Agriculture and Agri-food Canada, 850, Lincoln Rd,
Fredericton, NB E3B 4Z7; Prince Edward Island Potato Board, 90 Hillstrom Ave, Charlottetown, PE C1E
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2C6; Saint-Jean-sur-Richelieu Research and Development Centre, Agriculture and Agri-food Canada,
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Saint-Jean-sur-Richelieu, QC J3B 3E6; and Prince Edward Island Department of Agriculture, PO Box
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2000, Charlottetown, PE C1A 7N8
Correspondence to: dahu.chen@agr.gc.ca

A survey of New Brunswick (NB) and Prince Edward Island (PEI) potato fields in crop rotation phase prior
to potato production was conducted in fall (October and November) between 2017 and 2021. A total of
114 and 122 fields for NB and PEI, respectively, were surveyed with 20 to 35 fields each year tested in
each province. Root lesion nematodes (RLN, Pratylenchus spp.) were detected in 99 and 98% of the
fields for NB and PEI, respectively, and two root lesion nematode species, P. crenatus and P. penetrans,
were identified in both provinces from 2017 to 2021. Based on 2019 and 2020 results, P. crenatus was
detected in 100% of surveyed fields in both NB and PEI, while P. penetrans was detected in 29% of the
fields in NB and 43% of the fields in PEI. P. crenatus accounted for 92 and 89% of the populations for NB
and PEI, respectively, while P. penetrans accounted for 8 and 11%, respectively. Verticillium dahliae was
detected in 94 and 95% potato fields in NB and PEI, respectively. All isolates obtained from potato cv.
Russet Burbank in a baiting trial were V. dahliae, belonging to two lineages. V. albo-atrum was detected
in a few fields at very low level, except two fields in NB where the V. albo-atrum was predominating over
the V. dahliae. Previous crops did not affect V. dahliae population densities for NB and PEI, and did not
affect RLN population in NB, but significantly affected RLN in PEI. Fall cover crop did not affect the
populations of RLN and V. dahliae in PEI. The present study revealed that the potato pathogenic root
lesion nematode P. penetrans was present in less than 50% of surveyed fields and accounted for around
10% of root lesion nematode population in NB and PEI, and V. dahliae was the dominant species and
present in greater than 90% of surveyed fields in both provinces.

[O95] IMPACT OF CROP ROTATION ON THE MICROBIOMES OF SUDDEN DEATH SYNDROME
(SDS) AND SOYBEAN CYST NEMATODE (SCN) SUPPRESSIVE SOILS OF SOYBEANS IN
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SOUTHERN ONTARIO, CANADA. R. Malla , L.A. Phillips , K.E. Dunfield , B.Seuradge , A. Wragg ,
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and O.S. Wally . School of Environmental Sciences, OAC, University of Guelph, 50 Stone Rd E,
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Guelph, ON N1G 2W1, Canada; and Harrow Research and Development Centre, Agriculture and Agri-
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Food Canada, 2585 County Road 20, Harrow, ON N0R 1G0, Canada
*Corresponding and presenting author
Correspondence to: owen.wally@agr.gc.ca

Sudden Death Syndrome (SDS), caused by Fusarium virguliforme, and Soybean Cyst Nematode (SCN),
Heterodera glycines, pose significant threats to North American soybean production, with annual losses
exceeding $1.3 billion USD. This study compares a long-term soybean monoculture in Essex, Ontario,
which exhibits low levels of SDS and SCN, with a traditionally rotated field in Chatham, Ontario, where
similar disease suppression is not observed. Analysis up to 2023 indicates that rotational practices in
fields prone to SDS can reduce disease severity by 45% and increase yields by 48% over six years.
Soybeans in maturity group 1 (MG1) experience yield reductions in rotated plots, while yields for maturity
group 2 (MG2) remain stable, suggesting that disease suppressiveness can be rapidly induced,
potentially within five years. Reintroducing rotation in the Essex site led to minor yield changes and a
slight increase in disease levels, but these remained lower than in previous years, suggesting the
medium-term durability of soil suppressiveness. Our methods include growth room bioassays and
bacterial and fungal taxonomic amplicon sequencing of soil and cyst samples collected in both spring and
fall of all study years, to analyze soil microbiome dynamics and the relationship between SCN presence
and SDS severity. Sequencing data was processed using a customized dada2 pipeline to identify
amplicon sequence variants. Results indicate that soybean monoculture promotes greater species
richness and diversity in suppressive soils compared to rotated crops. Overall microbial community
composition was evaluated using ordination techniques and PERMANOVAs. Our ongoing molecular and
microbiological studies are focused on elucidating the mechanisms behind soil-mediated disease
suppression in soybeans, with a particular emphasis on the interaction between SCN and SDS. This

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