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The dispensable chromosome of L eptosphaeria maculans shelters an effector gene conferring avirulence towards B rassica rapa
Author(s) -
Balesdent MarieHélène,
Fudal Isabelle,
Ollivier Bénédicte,
Bally Pascal,
Grandaubert Jonathan,
Eber Frédérique,
Chèvre AnneMarie,
Leflon Martine,
Rouxel Thierry
Publication year - 2013
Publication title -
new phytologist
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.742
H-Index - 244
eISSN - 1469-8137
pISSN - 0028-646X
DOI - 10.1111/nph.12178
Subject(s) - minichromosome , leptosphaeria maculans , biology , genetics , brassica rapa , canker , gene , complementation , phenotype , chromosome , botany
Summary Phytopathogenic fungi frequently contain dispensable chromosomes, some of which contribute to host range or pathogenicity. In L eptosphaeria maculans , the stem canker agent of oilseed rape ( B rassica napu s), the minichromosome was previously suggested to be dispensable, without evidence for any role in pathogenicity. Using genetic and genomic approaches, we investigated the inheritance and molecular determinant of an L . maculans – B rassica rapa incompatible interaction. Single gene control of the resistance was found, while all markers located on the L . maculans minichromosome, absent in the virulent parental isolate, co‐segregated with the avirulent phenotype. Only one candidate avirulence gene was identified on the minichromosome, validated by complementation experiments and termed AvrLm11 . The minichromosome was frequently lost following meiosis, but the frequency of isolates lacking it remained stable in field populations sampled at a 10‐yr time interval, despite a yearly sexual stage in the L . maculans life cycle. This work led to the cloning of a new ‘lost in the middle of nowhere’ avirulence gene of L . maculans , interacting with a B . rapa resistance gene termed R lm11 and introgressed into B . napus . It demonstrated the dispensability of the L . maculans minichromosome and suggested that its loss generates a fitness deficit.