# Conserved ‘Late’ Effector Genes From Leptosphaeria maculans Inducing Gene‐For‐Gene Quantitative Resistance in Brassica napus Semi‐Winter Genotypes

## TL;DR

This study identifies new durable resistance sources in Brassica napus against a fungal pathogen by focusing on conserved late effector genes.

## Contribution

The paper discovers that late effector genes are more conserved and can trigger durable resistance in semi-winter Brassica napus genotypes.

## Key findings

- Late effector genes differ from early ones in genomic characteristics and are more conserved.
- New resistance sources were found in semi-winter Brassica napus genotypes against late effectors.
- Late effector genes are overexpressed during stem infection and located in stable genomic regions.

## Abstract

Leptosphaeria maculans is a phytopathogenic fungus responsible for stem canker on
Brassica napus
. Its infectious cycle goes through an early phase of leaf infection and a late phase of colonisation and infection of the stem. The disease is mainly controlled by plant genetic resistances targeting a limited set of early fungal effector genes overexpressed during leaf infection and located in dynamic repeat‐rich genomic regions. Thus, these resistances can be rapidly overcome by the pathogen. To find new sources of resistance, we focused on late effector genes, expressed during stem infection and located in gene‐rich regions. A previous study revealed a quantitative resistance in the stem, partly relying on a gene‐for‐gene interaction with a late effector gene. In this study, we deciphered whether all late effector genes shared the same genomic and evolutionary characteristics and if they could be more stable than early effector genes, rendering the resistance they trigger more durable. In addition, as previous studies highlighted new criteria for selecting late effectors and suggested
B. napus
semi‐winter genotypes as an interesting genetic pool for uncovering resistance sources, we selected six new late effector gene candidates and screened an enlarged panel of semi‐winter genotypes. We revealed that early and late effector genes diverged for most of their genomic characteristics, supporting the hypothesis of late effector genes being more conserved. Moreover, we revealed new resistance sources to late effector genes, almost all belonging to the semi‐winter genetic pool, validating their importance to uncover new resistance sources.

To uncover new durable resistance sources to Leptosphaeria maculans in
Brassica napus
, we targeted late effector genes, located in conserved genomic regions and overexpressed during stem infection.