A two genes – for – one gene interaction between Leptosphaeria maculans and Brassica napus
Y. PETIT (1), A. Degrave (2), M. Meyer (2), F. Blaise (2), B. Ollivier (2), T. Rouxel (2), I. Fudal (2), M. Balesdent (2) (1) French National Institute for Agronomical Research, France; (2) INRA/AgroParisTech UMR1290 BIOGER, France

Leptosphaeria maculans is a hemibiotophic ascomycete which causes stem canker of oilseed rape. That phytopathogenic fungus interacts with its host (Brassica napus) according to the gene-for-gene concept. The most economically and environment friendly method of control of stem canker is the genetic control by using host resistance. Single gene resistance is extremely efficient, but races of the pathogen virulent towards a resistance gene can appear in a few years and necessitates continuously new breeding programs. Moreover, specific resistances are rare in oilseed rape, and a lot of efforts are made to find other resistance genes in other Brassica species. To date, 11 interactions were genetically characterized between L. maculans avirulence genes and corresponding resistance genes in Brassica. Recently, the avirulence gene AvrLm10 which is recognized by the resistance gene Rlm10 of the black mustard has been cloned. AvrLm10 corresponds in fact to two avirulence genes AvrLm10_1 and AvrLm10_2. Each of them is necessary but not sufficient to induce resistance towards Rlm10. Silencing of one of those genes is sufficient to abolish recognition by Rlm10. That interaction of two avirulence genes against one resistance gene is therefore different from the classical gene-for-gene concept. It suggests that AvrLm10_1 and AvrLm10_2 could directly interact and / or that they could target the same plant protein. A Y2H screen suggested a direct interaction between AvrLm10-1 and AvrLm10-2. This interaction was confirmed with Bimolecular Fluorescence Complementation (BiFC) experiments.

Abstract Number: P7-199
Session Type: Poster