A cDNA microarray approach to decipher sunflower (Helianthus annuus) responses to the necrotrophic fungus Phoma macdonaldii

To identify the genes involved in the partial resistance of sunflower (Helianthus annuus) to the necrotrophic fungus Phoma macdonaldii, we developed a 1000‐element cDNA microarray containing carefully chosen genes putatively involved in primary metabolic pathways, signal transduction and biotic stress responses. A two‐pass general linear model was used to normalize the data and then to detect differentially expressed genes. This method allowed us to identify 38 genes differentially expressed among genotypes, treatments and times, mainly belonging to plant defense, signaling pathways and amino acid metabolism. Based on a set of genes whose differential expression was highly significant, we propose a model in which negative regulation of a dual‐specificity MAPK phosphatase could be implicated in sunflower defense mechanisms against the pathogen. The resulting activation of the MAP kinase cascade could subsequently trigger defense responses (e.g. thaumatin biosynthesis and phenylalanine ammonia lyase activation), under the control of transcription factors belonging to MYB and WRKY families. Concurrently, the activation of protein phosphatase 2A (PP2A), which is implicated in cell death inhibition, could limit pathogen development. The results reported here provide a valuable first step towards the understanding and analysis of the P. macdonaldii–sunflower interaction

Phoma et dessèchement précoce du tournesol

Cet ouvrage fait le point sur le phoma et le dessèchement précoce du tournesol : connaissances actuelles sur le champignon et la maladie, méthodes de contamination, impact de la conduite de culture, résistance génétique du tournesol au phoma, méthodes de lutte. Il fait suite à de nombreux travaux de recherche, menés principalement en France depuis 5 ans dans le cadre de l’UMT Tournesol à Toulouse par les équipes du CETIOM, de l’EI Purpan, de l’ENSAT et de l’INRA

Control of Verticillium dahliae causing sunflower wilt using Brassica cover crops

Since 2010, sunflower in France has been severely affected by a vascular wilt disease caused by Verticillium dahliae. Disease is widespread and causes significant damage up to 30% yield loss. V. dahliaeis a soil-borne fungus living in roots able to survive in the absence of a host in the form of microsclerotia (MS). Brassica crops used as cover crops can naturally suppress soilborne pathogen viability. This fumigation activity has been linked to volatile isothiocyanates (ITCs) released from glucosinolates (GSLs). In this study, Brassicacover crops of white and brow mustard, radish, rape and rapeseed were evaluated for their ability to reduce the viability and development of V. dahliae. Cultivars were selected by GSL side-chain and concentration, and V. dahliaestrain for its aggressiveness on sunflower. Biofumigation was assessed in a laboratory assay. MS and developed V. dahliaeon growing media were exposed for 20 days to volatile compounds released by fresh or freeze ground plant tissues. The toxicity of ITCs-GSLs on V. dahliaewas assessed by the area under fungus progress curve relating its development on the media. The five Brassicareduced the development and germination of V. dahliaeby 90% (brown-mustard) to 63% (radish), and the development by 90% (rape) to 69% (white-mustard) compared to the control in absence of tissues. Aliphatic GSLs in brown mustard and rape, and indole GSLs in rape and radish may explain the strong reduction of V. dahliaedevelopment and viability respectively. These results indicate that Brassica have potential for use as cover crops for the control of soilborne disease problems and sunflower wilt

Phoma et dessèchement précoce du tournesol

Cet ouvrage fait le point sur le phoma et le dessèchement précoce du tournesol : connaissances actuelles sur le champignon et la maladie, méthodes de contamination, impact de la conduite de culture, résistance génétique du tournesol au phoma, méthodes de lutte. Il fait suite à de nombreux travaux de recherche, menés principalement en France depuis 5 ans dans le cadre de l’UMT Tournesol à Toulouse par les équipes du CETIOM, de l’EI Purpan, de l’ENSAT et de l’INRA