AUTHOR=Zhang Qiang , Dandena Hanna , McCausland Madison , Liu Huizhi , Liu Zheng , Xu Wen , Li Genyi 

TITLE=Genetic Analysis of a Horizontal Resistance Locus BLMR2 in Brassica napus

JOURNAL=Frontiers in Plant Science

VOLUME=12

YEAR=2021

URL=https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2021.663868

DOI=10.3389/fpls.2021.663868

ISSN=1664-462X

ABSTRACT=<p><italic>Leptosphaeria maculans</italic> causes blackleg disease in <italic>Brassica napus</italic>. The blackleg disease is mainly controlled by resistance genes in <italic>B. napus</italic>. Previous studies have shown that the blackleg resistant <italic>BLMR2</italic> locus that conferred horizontal resistance under field conditions, is located on chromosome A10 of <italic>B. napus</italic>. The purpose of this study is to fine map this locus and hence identify a candidate gene underlying horizontal resistance. The spectrum of resistance to <italic>L. maculans</italic> isolates of the resistance locus <italic>BLMR2</italic> was analyzed using near isogenic lines, resistant, and susceptible cultivars. The results showed that this locus was horizontally resistant to all isolates tested. Sequence characterized amplified regions (SCAR), simple sequence repeats (SSR), and single nucleotide polymorphism (SNP) markers were developed in the chromosome region of <italic>BLMR2</italic> and a fine genetic map was constructed. Two molecular markers narrowed <italic>BLMR2</italic> in a 53.37 kb region where six genes were annotated. Among the six annotated genes, <italic>BnaA10g11280D/BnaA10g11290D</italic> encoding a cytochrome P450 protein were predicted as the candidate of <italic>BLMR2</italic>. Based on the profiling of pathogen induced transcriptome, three expressed genes in the six annotated genes were identified while only cytochrome <italic>P450</italic> showed upregulation. The candidate corresponds to the gene involved in the indole glucosinolate biosynthesis pathway and plant basal defense in <italic>Arabidopsis thaliana</italic>. The molecular markers identified in this study will allow the quick incorporation of the <italic>BLMR2</italic> allele in rapeseed cultivars to enhance blackleg resistance.</p>