Abstract
Among the Brassica oilseeds, canola (Brassica napus) is the most economically significant globally. However, its production can be limited by blackleg disease, caused by the fungal pathogen Lepstosphaeria maculans. The deployment of resistance genes has been implemented as one of the key strategies to manage the disease. Genetic resistance against blackleg comes in two forms: qualitative resistance, controlled by a single, major resistance gene (R gene), and quantitative resistance (QR), controlled by numerous, small effect loci. R-gene-mediated blackleg resistance has been extensively studied, wherein several genomic regions harbouring R genes against L. maculans have been identified and three of these genes were cloned. These studies advance our understanding of the mechanism of R gene and pathogen avirulence (Avr) gene interaction. Notably, these studies revealed a more complex interaction than originally thought. Advances in genomics help unravel these complexities, providing insights into the genes and genetic factors towards improving blackleg resistance. Here, we aim to discuss the existing R-gene-mediated resistance, make a summary of candidate R genes against the disease, and emphasise the role of players involved in the pathogenicity and resistance. The comprehensive result will allow breeders to improve resistance to L. maculans, thereby increasing yield.
Highlights
The Brassicaceae family consists of diverse members, comprised of 372 genera and 4060 species [1]
This review focuses on the gene for gene mechanism of blackleg resistance, resistance gene (R gene) content in canola and its relatives, candidate blackleg R genes, genetic factors in L. maculans pathogenicity and resistance, and future work that can advance knowledge towards a more resistant canola crop
L. maculans can adapt to the host over time in the field
Summary
The Brassicaceae family consists of diverse members, comprised of 372 genera and 4060 species [1]. The members include, but are not limited to, domesticated and wild root vegetables like turnip Gemmifera), mustards (Brassica juncea, Brassica nigra, Brassica carinata, Brassica elongata, Hirschfeldia incana, Sinapis arvensis, Sinapis alba), oilseed crops (B. napus, B. rapa, B. juncea, Camelina sativa), and a model plant (Arabidopsis thaliana). B. carinata (BBCC, 2n = 4x = 34), as shown in the triangle of U [2] These Brassicaceae plant species have gained economic importance as condiments, dyes, medicinal uses, scientific models, ornamentals, vegetables, and the profitable canola oilseed [3,4,5,6,7,8]. The world export rate for canola oil and derived products is expected to rise from 20% to 40% in the coming years [13]
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