Page 206 - Plant Canada 2024 Proceeding

PLANT CANADA 2024

Clubroot, a swollen gall or club-shaped root, is a devastating disease of Brassicas caused by
Plasmodiophora brassicae, a soil-borne obligate biotrophic plant pathogen. Clubroot management
programs have been developed throughout the world to try to mitigate this problem. Unfortunately, these
strategies have been unsuccessful in limiting the spread of the disease. To successfully colonize plants,
pathogens secrete a wide range of effectors that interact with host targets to manipulate the host
physiology or deregulate host immune responses. PbPE29 is an effector secreted by P. brassicae during
the secondary stage (initiated between 5-7 days post inoculation (dpi) with resting spores) of pathogen
infection of Arabidopsis roots. Transcript of PbPE29 is expressed between 14-28 dpi – late secondary
stage of infection and during the development of galls on the roots of infected plants. Transient
expression of PbPE29-GFP and ∆SP PbPE29-GFP (minus signal peptide) in N. benthamiana leaves, show
endoplasmic reticulum and nuclear localization, respectively. Neither PbPE29-GFP nor ∆SP PbPE29-GFP
induce PCD when transiently expressed in N. benthamiana leaves. Uninfected transgenic Arabidopsis
lines, over-expressing PbPE29 and PbPE29-FLAG, show WT phenotype, however, 21 dpi with P.
brassicae resting spores, the roots of both transgenic lines appear to be more susceptible to infection and
produce more galls when compared to WT roots. We are currently working on the molecular interaction,
function and mechanism of PbPE29, and its role in clubroot gall formation.

*[P4] EVALUATION OF WHEAT FOR RESISTANCE TO BACTERIAL LEAF STREAK UNDER
CONTROLLED CONDITIONS. Valentina Anastasini , T. Kelly Turkington , Constanza Fleitas , and Randy
1
1
2
Kutcher . Cereal and Flax Pathology Group, Department of Plant Sciences, University of Saskatchewan,
1 1
College of Agriculture and Bioresources, 51 Campus Drive, Saskatoon, SK, Canada, S7N 5A8; and
2 Lacombe Research and Development Centre, Agriculture and Agri-Food Canada, 6000 C and E Trail,
Lacombe, Alberta, Canada
Correspondence to: randy.kutcher@usask.ca

Bacterial leaf streak (BLS) is a significant threat to cereal crops, particularly in the Prairies of Canada and
the United States. This emerging foliar disease, caused by Xanthomonas translucens, has increased in
the past decade, affecting numerous cultivated and non-cultivated cereal species. The pathogen is
classified into pathovar (pv) based on adaptation to host species; pv. undulosa has the greatest effect on
wheat. An effective disease management program is dependent on timely and correct identification of the
causal agent. Control strategies for the management of BLS in cereals crops are limited. Development of
BLS resistance wheat cultivars is a crucial strategy, but a long-term process. We have initiated a search
for wheat germplasm with resistance to BLS. The main objective is to identify potentially resistant
commercial varieties and promising sources of resistance in a diverse panel of wheat genotypes.
Germplasm will be evaluated under both field and controlled conditions. At present, we have assessed 96
registered durum and bread wheat varieties.

[P5] EXPLORING THE DIVERSITY OF STREPTOMYCES BACTERIA CAUSING COMMON SCAB
DISEASE IN NEWFOUNDLAND. Artho Baroi , Matthew Drodge , Gustavo A. Díaz Cruz , and Dawn R.
1
1
1,2
1 1
D. Bignell . Department of Biology, Memorial University of Newfoundland, 45 Arctic Avenue, St. John’s,
NL, Canada, A1C 5S7; and Phytopathology Department, Plant Protection Research Center (CIPROC),
2
Agronomy School, Universidad de Costa Rica, San Jose, Costa Rica
Correspondence to: dbignell@mun.ca

Common scab (CS) is a disease that has a negative impact on the quality and market value of seed,
processing and table stock potatoes. The disease is characterized by the presence of necrotic scab-like
lesions on the surface of affected tubers. Although potato is the most economically important host for the
disease, other root crops such as beet, carrot, and parsnip can also be affected. CS is caused by several
different species of soilborne bacteria belonging to the genus Streptomyces, of which Streptomyces
scabiei is the first described and is the best characterized. S. scabiei and other CS pathogens produce a
phytotoxic specialized metabolite called thaxtomin A, which functions as a plant cellulose biosynthesis
inhibitor and is the principal pathogenicity determinant responsible for CS development. In addition, other
phytotoxic specialized metabolites are thought to contribute to disease symptom development or severity
by some Streptomyces species. A previous study conducted by our lab investigated the Streptomyces
species responsible for potato CS on the island of Newfoundland, Canada. This study identified the
thaxtomin-producing Streptomyces europaeiscabiei as a probable causative agent of CS in
Newfoundland, and a novel plant pathogenic Streptomyces strain that does not produce thaxtomin A was

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