Page 145 - Plant Canada 2024 Proceeding

PLANT CANADA 2024

genome is highly conserved and suitable for variant-insensitive detection by PCR. The blueberry
Luteovirus genome sequences are ~5 kbp long and contain four potential open reading frames (ORF) for
RNA-dependent RNA polymerase (RdRP) P1, P2 proteins, CP, and CP read-through protein. The two
Luteoviruses, N and M2, have 84 % sequence similarity to each other. The sequence similarity between
blueberry virus M (GenBank ID OR051501.1) and M2 indicated that M2 is a variant of the blueberry virus
M. We confirmed the blueberry virus N and M2 assemblies by nanopore sequencing. We found that either
of the Luteoviruses were widely present in two populations of diseased plants (91% and 93%) and
present in healthy plants in fields as well as in nurseries. The blueberry tlaRNA assemblies are ~3 kbp
long and lack a CP but contain an ORF to encode RdRP. While we have no evidence that the
Luteoviruses cause disease, preliminary NGS results indicate that blueberry Luteovirus together with
tlaRNA is overrepresented in diseased plants that lack the usual suspects Scorch and Shoch virus. Thus,
we hypothesized that Luteovirus may act as a ‘helper virus’ for associated tlaRNAs to generate a hitherto
unknown complex cause of symptoms in diseased blueberry plants. We are testing this hypothesis by
single and mixed infections to observe symptom development and virus accumulation.

*[O87] A CLUBROOT PATHOGEN EFFECTOR DISRUPT AUXIN HOMEOSTASIS TO PROMOTE
COLONIZATION. Melaine González García , Marina Silvestre Vano , Soham Mukhopadhyay , Ian
1
1
1
1 1
Major , and Edel Pérez López . Department of Plant Sciences, Faculté des Sciences de l’Agriculture et
2
de l’Alimentation (FSAA), Université Laval, Quebec City, QC G1V 0A6, Canada; and Laurentian Forestry

2
Centre, 1055 Du PEPS Street, Quebec City, QC G1V 4C7, Canada
Correspondence to: lopez@fsaa.ulaval.ca

Clubroot is a devastating disease caused by the obligate biotrophic protist Plasmodiophora brassicae.
This disease is characterized by root swelling, which is related to alterations in host hormone metabolism,
primarily involving auxins and cytokinins. In this study, we examined the role of an auxin-responsive
Gretchen Hagen 3 effector from Plasmodiophora brassicae (PbGH3). The Gretchen Hagen 3 family,
widely distributed across the plant kingdom, conjugates various amino acids to plant hormones.
Previously, it was reported that PbGH3 conjugates auxins and jasmonic acid with proteinogenic amino
acids in vitro; however, the role of this protein during clubroot infection remains unknown. We generated
Arabidopsis thaliana lines overexpressing PbGH3 to study their phenotype and response to clubroot
infection. Initially, we examined morphological changes throughout the plant growth and development
across the entire plant life cycle. Our findings revealed that PbGH3 lines have shorter stems compared to
the Col-0 wild type ecotype, while their main roots are longer. Additionally, these lines exhibit longer
lateral roots and a higher density of root hairs in the maturation zone. We analyzed the auxin profile in the
roots of PbGH3 lines and Col-0 to identify any differences in plant hormone metabolism induced by the
expression of PbGH3. Furthermore, after germination, both Col-0 and PbGH3 lines were transplanted into
different concentrations of indole-3-acetic acid (IAA) to investigate their tolerance to the exogenous
application of the hormone. Both showed a decrease in root length; however, the effect was more
pronounced in Col-0. We also monitored the expression of PbGH3 during clubroot infection in Col-0 at
several time points, noting very early expression at 2 days post-inoculation. Considering this, we
quantified Pb in Col-0 and transgenic lines during early infection. Altogether, our results suggest that
PbGH3 induces an auxin-mediated increase in main root length and lateral root number, favoring
infection during early colonization of the susceptible host.

*[O88] RNASEQ STUDY OF PARTIALLY RESISTANT AND SUSCEPTIBLE PEA GENOTYPES UPON
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FUSARIUM AVENACEUM INFECTION. Sijan Pandit , Eoin O’Hara , Robert Gruninger , and Syama
1,2
Chatterton . University of Lethbridge, 4401 University Drive, Lethbridge, AB, T1K 3M4, Canada; and
2 1
2 Lethbridge Research and Development Centre, Agriculture and Agri-Food Canada, 5403–1 Avenue
South Lethbridge, AB, T1J 4B1, Canada
Correspondence to: syama.chatterton@agr.gc.ca

Fusarium root rot, as part of the pea root rot complex (PRRC), is caused by a number of Fusarium
species and is among the most devastating soil-borne diseases of field pea, causing complete yield loss
in severe conditions. The generalist pathogen Fusarium avenaceum was identified as the predominant
pathogen in the PRRC in Alberta. It can be difficult to manage because of its generalist lifestyle including
multiple hosts in over 80 genera of plant communities. This study aimed to understand plant responses
conferring partial resistance to F. avenaceum observed in some pea breeding lines. We evaluated

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