Introgression of blackleg resistance genes from related Brassica species to B. napus

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Shah, Keval Pravinchandra
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Canola (Brassica napus L.) is one of the most important oilseed crops, contributing more than $26 billion annually to the Canadian economy. Blackleg is caused by fungal plant pathogen Leptosphaeria maculans (Desm) Ces. et de Not. In canola, blackleg disease causes more than $1 billion in yield losses globally. There are different disease management strategies, and using resistant cultivars is one of the economically viable and environmentally sustainable approaches. There are reports of a breakdown of blackleg disease resistance in Australia, France, and Canada due to severe pathogen pressure. Twenty-two blackleg-specific resistance genes have been identified in different Brassica species. Out of these, the B-genome blackleg-specific resistance genes provide resistance throughout a plant's life. This thesis addresses the identification of putative novel sources of resistance from Brassica juncea and hexaploid Brassica into B. napus. In the first project, different B. juncea UM lines were used to identify a high level of resistance against blackleg disease and were screened with L maculans isolate 03-15-03 (AvrLm2, AvrLm3, AvrLm5-9, AvrLm6, AvrLm10, and AvrLm11) and PG4-1-M (AvrLm2, AvrLm5-9, AvrLm6, AvrLm10, and AvrLm11). Plants were inoculated with different L. maculans (AvrLm3 and avrLm3; AvrLm5 AvrLm6, AvrLm5 avrLm6, and avrLm5 avrLm6) isolates to identify the novel source of resistance in Brassica napus Westar x Brassica juncea UM3073 (UMBJ16) genotypes. For genotyping, UMBJ16 genotypes were tested for all the available blackleg-specific resistance gene-linked Kompetitive Allele-Specific PCR (KASP) (Rlm1, Rlm2, Rlm3, Rlm4, Rlm7, Rlm9, LepR1, LepR2, LepR3, and LepR4) and Simple Sequence Repeats (SSR) markers (Rlm6 and rjlm2). In the second project, the B-genome blackleg-specific resistance genes were introgressed from hexaploid Brassica into B. napus. Similar phenotyping and genotyping approaches were followed to identify the putative novel source of resistance against L. maculans isolate 03-15-03 and PG4-1-M in Brassica napus Westar x hexaploid Brassica crosses (BNHB16). This resulted in the identification of a putative novel source of resistance against L. maculans isolate PG4-1-M in UMBJ16 and BNHB16 genotypes. This newly developed germplasm will help to develop blackleg-resistant breeding material in canola and rapeseed breeding programs.
Brassica napus, Brassica juncea, hexaploid Brassica, KASP marker, SSR marker, blackleg, canola, Leptosphaeria maculans, resistance breeding