Évaluation du risque simplifiée du tomato brown rugose fruit virus pour la France métropolitaine: Avis de l'Anses. Rapport d'expertise collective

Évaluation du risque simplifiée du tomato brown rugose fruit virus pour la France métropolitaine. Avis de l'Anses. Rapport d'expertise collectiv

Life, death and rebirth of avirulence effectors in a fungal pathogen of Brassica crops, Leptosphaeria maculans

In agricultural systems, major (R) genes for resistance in plants exert strong selection pressure on cognate/ corresponding avirulence effector genes of phytopathogens. However, a complex interplay often exists between trade- offs linked to effector function and the need to escape R gene recognition. Here, using the Leptosphaeria maculans- oilseed rape pathosystem we review evolution of effectors submitted to multiple resistance gene selection. Characteristics of this pathosystem include a crop in which resistance genes have been deployed intensively resulting in ` boom and bust ' cycles; a fungal pathogen with a high adaptive potential in which seven avirulence genes are cloned and for which population surveys have been coupled with molecular analysis of events responsible for virulence. The mode of evolution of avirulence genes, all located in dispensable parts of the ' two-speed ' genome, is a highly dynamic gene- specific process. In some instances, avirulence genes are readily deleted under selection. However, others, even when located in the most plastic genome regions, undergo only limited point mutations or their avirulence phenotype is ` camouflaged ' by another avirulence gene. Thus, while hundreds of effector genes are present, some effectors are likely to have an important and nonredundant function, suggesting functional redundancy and dispensability of effectors might not be the rule

ELISA2000. Logiciel pour l'interprétation des résultats de tests ELISA

*INRA, Centre de Versailles Diffusion du document : INRA, Centre de VersaillesNational audienc

Effects of Leptosphaeria maculans race structure and fitness cost of virulence on management of phoma stem canker of oilseed rape

Fitness of virulent (avrLm1 and avrLm4) or avirulent (AvrLm1 and AvrLm4) isolates of Leptosphaeria maculans on Brassica napus without the corresponding resistance genes Rlm1 and Rlm4 was investigated in controlled environment (CE) and field experiments. Results indicate that there is a measurable fitness cost for virulent isolates compared to avirulent isolates in terms of number of lesions, size of lesions, distance grown through leaf tissue towards the petiole in CE experiments and in terms of systemic growth from leaf lesions to stems in field experiments. There were differences between the AvrLm1 and AvrLm4 loci in fitness cost. The optimal temperature for leaf infection was higher for AvrLm4 isolates than for AvrLm1 isolates. There was a cultivar effect on fitness cost of virulence at the AvrLm1 locus but not at the AvrLm4 locus. Results from field experiments suggest that on the same host without the corresponding Rlm1 and Rlm4 genes, AvrLm4 isolates were more fit than AvrLm1 isolates in warmer growing seasons. The fitness cost of virulence at the AvrLm1 locus was generally smaller than that at the AvrLm4 locus, suggesting that the corresponding resistance gene Rlm4 is more durable than Rlm1. Frequencies of avirulent AvrLm1 and AvrLm6 alleles in airborne inoculum for 2006/07, 2007/08 and 2008/09 growing seasons in the UK were investigated using quantitative PCR. There were differences in frequencies of AvrLm1 and AvrLm6 alleles in the three seasons. The detection of changes in frequencies of avirulent alleles provides essential information to guide deployment of cultivars with corresponding resistance genes to minimise the risk of breakdown of novel resistanceNon peer reviewe

Molecular phylogeny of the Leptosphaeria maculans-L. biglobosa species complex

International audienc

Species complex of fungal phytopathogens : Leptosphaeria maculans L biglobosa case study

International audienc

Genetic characterization of AvrLm1, the first avirulence gene of Leptosphaeria maculans

International audienc