Page 181 - PC2019 Program & Proceedings

PLANT CANADA 2019

S147. Developing a model for investigating pathogenesis by fungal hybrids using Ustilago maydis
and Sporisorium reilianum
*
Storfie, E. ; B. Saville
Trent University

We are developing a system to investigate fungal pathogen fusions using the model pathogen Ustilago
maydis and a closely related species, Sporisorium reilianum. Both infect maize; however, U. maydis
produces localized infections while S. reilianum infections are systemic. Preliminary RNA-seq analysis
from the hybrid dikaryons, induced to develop on plates, revealed a transcript population more similar to
U. maydis than to S. reilianum. Pathogenesis assays with the hybrid, U. maydis, and S. reilianum
dikaryons were carried out in which symptoms and pathogenesis gene transcript levels, determined using
species specific primers, were assessed during a time course of early disease development. The genes
assessed included U. maydis pathogenesis related transcription factors, cell signalling proteins, and
effectors as well as the orthologs of these genes in S. reilianum. The transcript levels were also compared
to those in dikaryons formed on plates. The reduced level of disease symptoms observed for the hybrid
was consistent with reductions in pathogenesis gene transcript levels. This suggests that experimentally
modifying pathogenesis gene expression would improve pathogenic development of the hybrid and make
it a viable model for investigating fungal hybrids and their pathogenesis. Modifying expression of select
genes is underway. All results will be discussed in terms fungal hybridization and providing a framework
for investigating hybrid formation and new pathogen emergence.

Emilee Storfie (emileestorfie@trentu.ca)

S148. Genome-wide-association studies on the resistance of rutabaga accessions to Plasmodiophora
brassicae isolates from Alberta, Canada
*
Yu, Z. ; R. Fredua-Agyeman; S. Hwang; S. Strelkov
University of Alberta

Clubroot, caused by Plasmodiophora brassicae Wor., is a devastating soil-borne disease of Brassica
crops worldwide. In this study, genomic regions associated with resistance to five single-spore isolates
(classified as pathotypes 2F, 3H, 5I, 6M, and 8N) and 12 field isolates (classified as pathotypes 2B, 3A,
3O, 5C, 5G, 5K, 5L, 5X, 8E, 8J and 8P) were investigated using 125 Brassica napus L. spp. napobrassica
(swede or rutabaga) accessions. The accessions were screened for resistance in greenhouse inoculation
experiments, while genotyping was conducted with a 15K Brassica SNP array. The rutabaga accessions
exhibited differential reactions towards the 17 isolates with 0.8 - 46.4% found to be resistant, 3.2 - 17.6%
moderately resistant and 37.6 - 94.4% susceptible. About 50.0% of the 13714 SNP markers used for
genotyping were included in the association studies, while those that did not meet specific filtering
criteria were discarded. One-hundred and five SNPs (71 on A01-A10 chromosomes and 34 on C genome
scaffolds) were found to be significantly (p<1E-06) associated with resistance to the 17 P. brassicae
isolates. Fifteen, nineteen and nine of SNPs associated with clubroot resistance was found respectively on
A02, A03 and A08, which is consistent with the previous identification of at least eleven clubroot-resistance
genes on these three chromosomes. The SNPs identified in this study will be important in the marker-
assisted breeding of clubroot-resistant canola.

Zhiyu Yu (zhiyu3@ualberta.ca)

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