AUTHOR=Neik Ting Xiang , Barbetti Martin J. , Batley Jacqueline 

TITLE=Current Status and Challenges in Identifying Disease Resistance Genes in Brassica napus

JOURNAL=Frontiers in Plant Science

VOLUME=8

YEAR=2017

URL=https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2017.01788

DOI=10.3389/fpls.2017.01788

ISSN=1664-462X

ABSTRACT=<p><italic>Brassica napus</italic> is an economically important crop across different continents including temperate and subtropical regions in Europe, Canada, South Asia, China and Australia. Its widespread cultivation also brings setbacks as it plays host to fungal, oomycete and chytrid pathogens that can lead to serious yield loss. For sustainable crop production, identification of resistance (<italic>R</italic>) genes in <italic>B. napus</italic> has become of critical importance. In this review, we discuss four key pathogens affecting <italic>Brassica</italic> crops: Clubroot (<italic>Plasmodiophora brassicae)</italic>, Blackleg (<italic>Leptosphaeria maculans</italic> and <italic>L. biglobosa)</italic>, Sclerotinia Stem Rot (<italic>Sclerotinia sclerotiorum</italic>), and Downy Mildew (<italic>Hyaloperonospora parasitica)</italic>. We first review current studies covering prevalence of these pathogens on <italic>Brassica</italic> crops and highlight the <italic>R</italic> genes and QTL that have been identified from <italic>Brassica</italic> species against these pathogens. Insights into the relationships between the pathogen and its <italic>Brassica</italic> host, the unique host resistance mechanisms and how these affect resistance outcomes is also presented. We discuss challenges in identification and deployment of <italic>R</italic> genes in <italic>B. napus</italic> in relation to highly specific genetic interactions between host subpopulations and pathogen pathotypes and emphasize the need for common or shared techniques and research materials or tighter collaboration between researchers to reconcile the inconsistencies in the research outcomes. Using current genomics tools, we provide examples of how characterization and cloning of <italic>R</italic> genes in <italic>B. napus</italic> can be carried out more effectively. Lastly, we put forward strategies to breed resistant cultivars through introgressions supported by genomic approaches and suggest prospects that can be implemented in the future for a better, pathogen-resistant <italic>B. napus</italic>.</p>