Page 126 - Plant Canada 2024 Proceeding

PLANT CANADA 2024

regression joint linkage QTL mapping and analysis by MapQTL were performed. Strongfield displayed a
resistance response across all the tests in Canada, but an intermediate to susceptible response at El
Batan, and a resistant response at Obregon, Mexico. Strongfield contributed seven QTL revealed by the
field data, and nine QTL conditioning seedling resistance. A major QTL was discovered on chromosome
3A of Strongfield. The 3A QTL showed resistance to all the tested Canadian Pt races during the seedling
stage and all the field tests in Canada; however, it was not effective in Mexico. A QTL on 1B from
Strongfield corresponded with the multi-pest resistance gene Lr46/Yr29. In addition to 1B, Strongfield
contributed one QTL at El Batan and two QTL at Obregon all revealed by single environments. Notably,
we found three new QTL donated from Blackbird or RL6089 that conferred resistance in the Mexican field
tests. The major QTL on 3A and most of the other QTL identified in Canada were not effective in Mexico,
suggesting the need for pre-emptive resistance breeding to fight against the imminent incursion of
Mexican races to Canadian wheat growing areas. The minor effect QTL identified in Mexico show the
potential power of pyramiding QTL to build on the existing foundation of Canadian durum wheat to protect
against these new leaf rust races in Mexico.

[O49] IDENTIFYING RESISTANCE (R) GENES TO BLACKLEG LEPTOSPHAERIA MACULANS IN
ACCESSIONS OF CANOLA. Oluwafemi Lawal and Dilantha Fernando . Department of Plant Science,
1
1 1
University of Manitoba, Winnipeg, Manitoba, Canada
Correspondence to: dilantha.fernando@umanitoba.ca

Canola (Brassica napus), as one of the most economically important crops in Canada, is challenged by a
constant arms race with Leptosphaeria maculans-blackleg causative agent. This led to the breakdown of
resistant (R) genes in most canola cultivars grown in Canada particularly in the Prairie, where canola is
mainly grown, leading to more than 30% yield reduction. Identifying the R gene is a precursor in breeding
for resistance to blackleg disease, which is the most effective method of protecting canola plants against
blackleg disease and its yield loss. Although resistant genes have been explored from other Brassica
species, their blackleg resistance potential and stability have not been exploited in the cultivars grown on
the farmers’ field. Therefore, this research sought to identify R genes from some B. napus accessions
sourced from China, where canola is believed to be resistant to blackleg disease, though caused
predominantly by L. biglobosa in China. To date, 60 Chinese accessions of canola have been screened
against 12 IBCN (International Blackleg of Crucifers Network) differential isolates of L. maculans. The
cotyledons of six plants were infected with each of the isolates at seven days post inoculation (dpi), and
rated at 10dpi and 14dpi on a scale of 1-9. With 1-3 = resistant, 5 = moderately susceptible, and 7-9 =
susceptible. Less than 1% of the Chinese accessions had good resistant scores. Although most
accessions were susceptible to L. maculans, there is still the high potential for identifying novel R genes
among Chinese accessions, as this is essential in breeding for blackleg resistance in canola.
Furthermore, the identified accessions were vernalized, grown to the booting stage, and crossed with
Westar. The F1 seeds of Chinese lines x Westar will be selfed to F2, screened with differential isolates of
L. maculans, and then subjected to bulk segregant analysis (BSA) to identify putative R gene. Together,
the identified R gene will provide more sources of R genes available in the pool to canola breeding
program for possible introgression and gene pyramiding towards improving sustainable resistance to
blackleg disease, enhancing canola yield, and alleviating the trade barriers usually imposed by importing
countries towards curtailing the spread of blackleg disease.

[O50] THE EFFECT OF R GENE ROTATION ON MITIGATION OF CANOLA BLACKLEG DISEASE IN
1
2
WESTERN CANADIAN PRAIRIES. Malini Anudya Jayawardana , Zhongwei Zou and Dilantha
Fernando . Department of Plant Science, University of Manitoba, Winnipeg, MB, R3T2N2 Canada; and
1 1
2 Department of Biology, Wilfrid Laurier University, Waterloo, Ontario, N2L 3C5 Canada
Correspondence to: dilantha.fernando@umanitoba.ca

Blackleg caused by the fungal pathogen Leptosphaeria maculans is one of the devastating diseases in
western Canada. Host resistance plays a major role among the management strategies currently
available to control blackleg. Host resistance in canola against blackleg is governed by both qualitative (R
genes) and quantitative resistance. However, the continuous exposure of the same R gene to the
pathogen over the years leads to the breakdown of its resistance. This is called R gene resistance
breakdown. To understand the delay in the R gene resistance breakdown, we have introduced a 4-year R
gene rotation study in three provinces Manitoba, Saskatchewan, and Alberta. We have included 11

125