Recent Findings Unravel Genes and Genetic Factors Underlying Leptosphaeria maculans Resistance in Brassica napus and Its Relatives

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.

Daisychain: Search and Interactive Visualisation of Homologs in Genome Assemblies

“…It is not possible for users to upload their own data but local instances of Daisychain with different datasets can be hosted using the code publicly available at https://github.com/AppliedBioinformatics/gene-daisychain under GNU Lesser General Public License v3. BnaA07g28760D [36], its 3′ and 5′ neighbors and other homologs in the B. napus v4.1 annotation [12] (grey circles), compared with the B. napus ZS11 annotation [16] (pink circle), the B. napus Tapidor annotation (orange circles) and the Darmor-bzh v8.1 annotation (blue circles) [14]. The B. napus v4.1 annotation contains 3 homologs for the candidate gene, while the ZS11 and Tapidor annotations both contain only one homolog.…”

“…Figure 3. Visualisation of gene homologies with Daisychain-Web for the disease resistance gene Rlm1 candidate geneBnaA07g28760D[36], its 3′ and 5′ neighbors and other homologs in the B. napus v4.1 annotation[12] (grey circles), compared with the B. napus ZS11 annotation[16] (pink circle), the B. napus Tapidor annotation (orange circles) and the Darmor-bzh v8.1 annotation (blue circles)[14]. The B. napus v4.1 annotation contains 3 homologs for the candidate gene, while the ZS11 and Tapidor annotations both contain only one homolog.…”

Pangenomes as a Resource to Accelerate Breeding of Under-Utilised Crop Species

“…These trait pangenomes aim to describe the landscape of genetic variation related to a trait. For example, resistance gene analogues (RGAs) have conserved domains and motifs that contribute to resistance to pathogens [ 102 , 103 , 104 , 105 ]. Thus, a pan-RGA can provide a platform to investigate the impact of genetic variation on plant resistance, as well as identify genetic markers for RGA profiling of species that may have limited genomic data [ 102 ].…”

Sustainability on the farm: breeding for resistance and management of major canola diseases in Canada contributing towards an IPM approach

“…In addition to Rlm6 and Rlm10 genes, LMJR1, LMJR2, and rjlm2 have been identified in the B genome. No Avr gene has been isolated/discovered for these R genes yet (Cantila et al 2021).…”

“…For example, some R genes (Rlm1, Rlm3, Rlm6, Rlm7, LepR1, and LepR3) have been reported to break down and lose effectiveness in the field due to sexual recombination of L. maculans and population changes (Van de Wouw et al 2010;Winter and Koopmann 2016;. This means there is a high risk of breakdown of a particular source of resistance, so canola farmers should be advised to utilize different R genes by crop rotation in canola cultivars to sustainably manage the blackleg infection and resistance breakdown (Zhang and Fernando 2018;Van de Wouw and Howlett 2020;Cantila et al 2021). Another strategy is gene stacking or pyramiding, in which a host contains several major resistance genes (Mundt 2018).…”