Page 155 - PC2019 Program & Proceedings

PLANT CANADA 2019

S95. Boost your yield, harness the forcefield: advancing RNAi-based biocontrols against agronomic
pathogens.
*
Wytinck, N. ; A. McLoughlin; D. Ziegler; D. Khan; D. Sullivan; S. Whyard; M. Belmonte
University of Manitoba

Crop species such as canola (Brassica napus), Canada’s most valuable oilseed, are under constant
pressure from phytopathogens which greatly decreases yield potentials. The highly aggressive
necrotroph, Sclerotinia sclerotiorum is an annual burden for producers. Despite continued efforts to
protect canola, there remains a direct and immediate need to find novel, sustainable methods to
specifically target single pathogens. RNA interference has emerged as a compelling control strategy to
impart plant protection against attack from agricultural pathogens through foliar sprays. While
applications of double stranded (ds) RNA molecules that specifically targets a single gene in Sclerotinia
has proven effective, the timing of the spray application remains a limitation. Thus, we developed canola
that constitutively expresses dsRNA that targets individual pathogenicity genes. In planta greenhouse
experiments suggest substantial resistance and we are now working to resolve the physiological and
molecular mechanisms occurring within these RNAi plants. In addition to the phenotypic differences in
lesion progression and severity, we have observed differing plant defence responses including with
hormone signalling during infection. Due to the dsRNA-mediated decrease in fungal pathogenicity, plants
are able to mount more effective defences and therefore cellular differences are observed at infection
sites. For example, tylose-composed ‘forcefields’ shield the inner stem tissue layers from
further Sclerotinia penetration and prevent lodging and complete yield loss. Ultimately, with continued
development, RNAi has the promise to be at the forefront of agricultural pest control as we move
towards a more ecologically-sound future.

Nick Wytinck (wytinckn@myumanitoba.ca)

S96. Gene editing to enhance pathogen-induced cell wall reinforcement resistance to late blight in
Russet Burbank potato
1
3
2
*1
Hegde, N. ; D. Doddamani ; Y. Kalenahalli ; N. Soni
1 McGill University
2 The Roslin Institute, The University of Edinburgh
3 University of Adelaide
Potato late blight, caused by the oomycete Phytophthora infestans, remains the major threat to potato
production. Pyramiding of leucine-rich-repeat (NB-LRR) receptor R genes and fungicide applications are
commonly used to manage late blight. However, the receptor R genes are not stable, and the fungicide
applications are often not adequate. Pathogen-induced metabolites can impart durable resistance to late
blight through active cell wall reinforcement at the site of infection. Several resistance R genes were
identified based on RNAseq of resistant and susceptible potato cultivars. A R gene, StCCoAOMT, with
known cell wall reinforcement resistance function was found polymorphic in Russet Burbank. A
CRISPR/Cas9-based genome editing was used to replace the polymorphic segment of this R gene in
Russet Burbank with a functional segment from a resistant potato genotype. The enhanced late blight
resistance of gene-edited Russet Burbank was confirmed under greenhouse conditions. Stacking of more
R genes can further enhance resistance. This technology can be used to improve resistance in more than
200 cultivars of potato currently being cultivated in Canada and more around the world.

Niranjan Hegde (niranjan.hegde@mail.mcgill.ca)

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