Page 161 - Plant Canada 2024 Proceeding

PLANT CANADA 2024

translocation process during P. brassicae infection, have yet to be identified. Here, we report the
identification of a P. brassicae plastid-associated effector (PAE), PbPAE, and propose a functional role(s)
during clubroot development. Transient expression of PbPAE-GFP, in the leaves of Nicotiana
benthamiana, shows chloroplast association and results in chlorosis. Through mutational analysis of the
effector the essential sequences for chloroplast association, leading to chlorosis, have been identified.
Overexpression of PbPAE-GFP in Arabidopsis supports its association with chloroplasts (and subsequent
chlorosis) but more importantly its association with amyloplasts in root tissues. Live cell imaging shows
PbPAE-GFP associated with amyloplasts in plant cells hosting P. brassicae secondary plasmodia.
Transgenic leaf chlorosis suggests that PbPAE is involved in promoting plastidial degenerative
processes. PbPAE interaction with the substrate recognizing adaptor protein (AtClpS1) of the Clp-
protease complex supports a role for PbPAE in modulating plastidial proteostasis and facilitating carbon
flow from host tissues to sustain pathogen development in infected plant roots. Furthermore, we have
subsequently identified a second P. brassicae plastid-associating effector, highlighting the importance of
amyloplast association with the plasmodial structure for the establishment of a nutrient sink and carbon
flow from host to the developing pathogen during disease progression.

*[O117] CLUBROOT RESISTANCE OF BRASSICA NAPUS INTROGRESSED FROM BRASSICA
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OLERACEA. Sonia Navvuru , Nat N.V. Kav , and Habibur Rahman . Department of Agricultural, Food
and Nutritional Science, 4-10 Agriculture/Forestry Centre, University of Alberta, Edmonton, AB T6G 2P5,
Canada
Correspondence to: hrahman@ualberta.ca

Brassica napus canola is affected by several biotic and abiotic stresses, including clubroot disease,
caused by Plasmodiophora brassicae, which can result in a yield loss of 29-90%. To date, the major
clubroot resistance (CR) genes of the Brassica A genome has been used in breeding clubroot resistant
cultivars; however, this type of resistance has been reported to become ineffective after cultivation for a
few years. Conversely, the C genome of B. oleracea carries resistance to a broad spectrum of pathotypes
but its potential in breeding clubroot resistant canola has not yet been exploited. We have developed
several B. napus lines (F10) carrying CR genes from B. oleracea. The objectives of this research were to
develop a genetically stable clubroot-resistant line and to understand the genetic control of the C genome
resistance. In order to accomplish this, 252 F10 plants descendent from 14 resistant and 5 partially
resistant F9 families were grown and inoculated with P. brassicae pathotype 3H, and the plants were
evaluated for fertility and CR at harvest. All plants were also self-pollinated to obtain F11 seeds and
crossed to a susceptible canola to obtain F1 seeds. Disease Severity Index (DSI) of the 14 resistant
families ranged from 0 to 100% with a mean of 39±6.20%, while the DSI for the partially resistant families
varied from 0 to 88.89% with a mean of 55.81±10.63%. In fact, three of the 14 resistant F10 families were
observed to be non-segregating, i.e. showed stability for resistance. Silique set under self-pollination (0-9
scale, where 9=good and 0=poor) and number seeds/siliques produced on crossing of the plants of the
14 resistant families ranged from 0 to 9 with a mean of 5.18±0.20, and 0 to 20 with a mean of 5.27±0.42,
respectively. For the partially resistant families, it varied from 0 to 9 with a mean of 5.34±0.29, and 0.00
to17.60 with a mean of 4.76±0.52, respectively. Most importantly, silique set of the three non-segregating
resistant families varied from 4 to 8 with a mean of 6.37±0.31, and seed set ranged from 0.00 to 16.75
with a mean of 7.46±1.20. Based on this, 28 F1s were selected and were grown along with their parents
to confirm their resistance. Different segregating populations including recombinant inbred lines (RILs) will
be developed to understand the genetic control of the CR and mapping of this resistance. Our research is
expected to facilitate the use of the C genome resistance in breeding and pyramiding with the A genome
resistance for durable CR in this crop.

[O118] MULTI-OMICS ANALYSIS OF MECHANISMS BEHIND THE “GAME OF HIDE AND SEEK” IN
THE BRASSICA NAPUS - LEPTOSPHAERIA MACULANS PATHOSYSTEM. Shuanglong Huang ,
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Peng Gao , Dilantha Fernando , and Gary Peng . Department of Plant Science, University of Manitoba,
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Winnipeg, MB R3T 2N2, Canada; and Agriculture and Agri-Food Canada, Saskatoon Research and
Development Centre, Saskatoon, SK S7N 0X2, Canada
Correspondence to: gary.peng@agr.gc.ca; dilantha.fernando@umanitoba.ca

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