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9. Schéma conceptuel des relations entre l'agent pathogène (Phoma seul ou complexe parasitaire), la plante hôte (le tournesol), l'environnement et la conduite de culture. Les cadres en violet et en vert correspondent aux variables liées aux agents pathogènes et au système de culture (SDC) respectivement. Seul les facteurs écrits en noir seront étudiés et testés expérimentalement pour l'étude sur l'étiologie du dessèchement précoce du tournesol.
Source publication
Le dessèchement précoce du tournesol résulte d'une infection de bas de tige par Phoma macdonaldii qui provoque une nécrose encerclante et un rétrécissement du diamètre du collet. Cette attaque entraine une sénescence foliaire brutale occasionnant des pertes dommageables pour la culture. Des contaminations artificielles par des spores ou du mycélium...
Citations
... Fungal diseases are often considered a severe constraint for the stability of sunflower yield. The most widespread and detrimental diseases in sunflower production are downy mildew (Plasmopara halstedii), verticillium wilt (Verticillium dahliae), phomopsis stem canker (Phomopsis helianthi), phoma black stem (Phoma macdonaldii) and white mould (Sclerotinia sclerotiorum) [3,12]. Growing sunflower frequently during a rotation favours the proliferation of these pathogens. ...
In south-western France, sunflowers are usually grown in short rotations and after a long fallow period during which soils are left bare. This practice can favour diseases, caused by soilborne fungi, such as sunflower verticillium wilt (SVW), as well as nitrate leaching, both of which can decrease yields. Growing cover crops during a fallow period is an agroecological practice that could provide ecosystem services and mitigate SVW. A Brassicaceae cover crop that causes biofumigation produces glucosinolates and liberate biocidal compounds that might regulate SVW biologically. Moreover, the green manure effect of the Fabaceae might increase soil mineral nitrogen (SMN). To go further, mixtures of Brassicaceae and Fabaceae might mutualise the benefits that each cover crop has in sole crops. A four-year field study in south-western France tested Brassicaceae (brown mustard, turnip rape and fodder radish) and Fabaceae (purple vetch) in sole crops or a mixture with two or three species during the fallow period, followed by biofumigation, and sunflower crop. The cover crops were characterised, SMN was measured, the SVW and yield were assessed and compared to those of the crop grown on soils left bare during the fallow period. Purple vetch as a sole crop cover crop significantly increased SMN before sunflower sowing but only in 2019. Fodder radish as a sole crop reduced SVW severity significantly, overall, 80 days after sowing, except in 2019, when weather conditions were unfavourable to biofumigation. Purple vetch as a sole crop also reduced significantly SVW severity in 2017 and 2020. Finally, sunflower yields after cover crops were higher than those after bare soils, only after purple vetch as a sole crop in 2020, with a mean increase of 0.77 t ha−1. Mixtures of Brassicaceae and Fabaceae sowed at these densities resulted in an intermediate SMN level between those in sole crops and the bare soil and they did not significantly decrease SVW or increase yields. Our results suggest that cover crops, especially fodder radish or purple vetch, and biofumigation can provide ecosystem services for sunflower, instead of leaving soils bare during the fallow period. However, the extent of ecosystem services is markedly affected by soil and climatic conditions as well as other management practices.
... At least 30 sunflower diseases are known. The most damaging and widespread fungal diseases are downy mildew (Plasmopara halstedii), phoma black stem (Phoma macdonaldii), phomopsis stem canker (Phomopsis helianthi), white mold (Sclerotinia sclerotiorum) and Verticillium wilt (Verticillium dahliae) (Seassau, 2010;Vear, 2016;Debaeke et al., 2017b), most of which are soilborne pathogens (P. halstedii, S. sclerotiorum, V. dahliae). ...
Sunflower (Helianthus annuus L.) is one of the three most productive oilseed crops worldwide. Soilborne diseases limit yields and are challenging to manage. The fungi Verticillium dahliae, Sclerotinia sclerotiorum and Macrophomina phaseolina can survive in the soil for many years and spread. Following the ban on fumigants, biofumigation, which consists of growing, chopping and incorporating a Brassicaceae cover crop to allow biocidal compounds production in the soil, may be an alternative. Biocidal effects of the hydrolysis of glucosinolate into active compounds, such as isothiocyanates, have been shown in laboratory studies, but the effectiveness of biofumigation varies more in the field. The present study reviews the main factors that determine effective biofumigation to protect sunflower. Since the toxicity of isothiocyanates to pathogens varies widely among the latter, we reviewed studies that assessed the suppressive effect of products of glucosinolate hydrolysis on V. dahliae, S. sclerotiorum and M. phaseolina. Farmers can use many mechanisms to increase isothiocyanate production, which may protect sunflower crop effectively. Increasing biomass production and chopping the cover crop during mild temperatures and before rainy periods could increase biofumigation effectiveness. Further field experiments are needed to confirm the potential of biofumigation to control soilborne diseases of sunflower and assess potential disservices to beneficial soil communities, given their potential key role in the control of soilborne pathogens.
... Pathogen infections are characterized by (1) a necrotic girdling spot at the stem base and on the stem, (2) early death of the leaf area, and (3) a small head. These symptoms lead to a global yield loss depending on the infection stage (Donald et al., 1987;Seassau, 2010;Seassau et al., 2010b). Studies carried out under controlled and field conditions in Europe and the United States of America have shown the role of Phoma macdonaldii as the causal agent of sunflower premature death, the other pathogens acting as opportunists (Donald et al., 1987;Seassau, 2010;Seassau et al., 2010b;Seassau et al., 2010c). ...
... These symptoms lead to a global yield loss depending on the infection stage (Donald et al., 1987;Seassau, 2010;Seassau et al., 2010b). Studies carried out under controlled and field conditions in Europe and the United States of America have shown the role of Phoma macdonaldii as the causal agent of sunflower premature death, the other pathogens acting as opportunists (Donald et al., 1987;Seassau, 2010;Seassau et al., 2010b;Seassau et al., 2010c). Phoma macdonaldii Boerema (Telomorph: Leptosphaeria lindquistii: McDonald, 1964) is one of the most important diseases in sunflower production, and has been reported worldwide (Gulya et al., 1997). ...
... There is no real chemical solution (Duroueix, 2005). However, sunflower genetic resistance (Al Fadil, 2006;Alignan, 2006;Al Fadil et al., 2009), crop rotation ( Jouffret, 2005), limited water supply after anthesis and additional nitrogen (Carson, 1991;Debaeke & Peres, 2003;Seassau, 2010;Seassau et al., 2010a) can significantly reduce the incidence of Phoma macdonaldii, and then premature ripening. The impact of the disease on yield has not been clearly assessed, but yield losses up to 1.3 t/ha have been reported in France (McDonald, 1964). ...
Resumen. El girasol (Helianthus annuus L.) es ampliamente cultivado
en Francia. Su aceite se destina principalmente a la alimentación
humana y a la industria verde. Su producción es consecuencia del rendimiento de la planta y del contenido de aceite, dependientes estos de la interacción planta–medio ambiente durante el ciclo. En el Sudoeste francés, se ha obtenido un avance reciente en el laboreo del suelo. En la actualidad, el 35% de la superficie dedicada al cultivo de girasol se realiza bajo labranza reducida. Las principales limitantes del cultivo lo constituyen el déficit hídrico y las enfermedades
criptogámicas. La infección con Phoma macdonaldii, conocida en la región como desecamiento precoz, es la segunda enfermedad en importancia del girasol en el sudoeste francés. Este trabajo tuvo por objetivo: 1) comprender cómo estos factores influyen sobre la producción de girasol, y 2) cuantificar la variación de la calidad de los ácidos grasos frente a las limitaciones impuestas por la reducción de labranzas y la infección con Phoma macdonaldii. Los resultados mostraron que: 1) la labranza del suelo influye sobre la composición en ácidos grasos del aceite de girasol, 2) el desecamiento precoz inducido por Phoma macdonaldii impacta en la nutrición de la planta por su efecto sobre los órganos (hojas, tallo, raíz), en el rendimiento y en sus componentes, y 3) la enfermedad influyó en la calidad del aceite y en el balance de ácidos grasos oleico vs. linoleico.
Palabras clave: Ácidos grasos; Aceite; Rendimiento; Desecamiento
precoz; Phoma macdonaldii; Labranza del suelo.
... Pathogen infections are characterized by (1) a necrotic girdling spot at the stem base and on the stem, (2) early death of the leaf area, and (3) a small head. These symptoms lead to a global yield loss depending on the infection stage (Donald et al., 1987;Seassau, 2010;Seassau et al., 2010b). Studies carried out under controlled and field conditions in Europe and the United States of America have shown the role of Phoma macdonaldii as the causal agent of sunflower premature death, the other pathogens acting as opportunists (Donald et al., 1987;Seassau, 2010;Seassau et al., 2010b;Seassau et al., 2010c). ...
... These symptoms lead to a global yield loss depending on the infection stage (Donald et al., 1987;Seassau, 2010;Seassau et al., 2010b). Studies carried out under controlled and field conditions in Europe and the United States of America have shown the role of Phoma macdonaldii as the causal agent of sunflower premature death, the other pathogens acting as opportunists (Donald et al., 1987;Seassau, 2010;Seassau et al., 2010b;Seassau et al., 2010c). Phoma macdonaldii Boerema (Telomorph: Leptosphaeria lindquistii: McDonald, 1964) is one of the most important diseases in sunflower production, and has been reported worldwide (Gulya et al., 1997). ...
... There is no real chemical solution (Duroueix, 2005). However, sunflower genetic resistance (Al Fadil, 2006;Alignan, 2006;Al Fadil et al., 2009), crop rotation ( Jouffret, 2005), limited water supply after anthesis and additional nitrogen (Carson, 1991;Debaeke & Peres, 2003;Seassau, 2010;Seassau et al., 2010a) can significantly reduce the incidence of Phoma macdonaldii, and then premature ripening. The impact of the disease on yield has not been clearly assessed, but yield losses up to 1.3 t/ha have been reported in France (McDonald, 1964). ...
The sunflower (Helianthus annuus L.) is largely cropped in France. Its oil is mainly used in human feeding and green industry. Oil yield depends on the plant yield and seed oil content depends in turn on the plant affected by environmental interactions during its growth cycle. The main limiting factors of the yield are drought stress and cryptogamic diseases. Soil tillage practices have known a recent evolution. In the South West of France 35% of the sunflower area are cropped without traditional tillage. Premature ripening caused by Phoma macdonaldii represents the second most important disease in the South West of France. Naturally infected plots were tested. The aim of this work was i) to understand how these factors act on sunflower production, and ii) to quantify the variation of fatty acid quality under this stress. The results showed i) variation of fatty acid under different tillage practices, ii) premature ripening attributed to Phoma macdonaldii has an impact on the plant organs linked to nutrition (leaves, stem, root) on yield and yield components; but also iii) that the disease influences seed quality, and the balance Oleic between Linoleic fatty acids.
Key words: Fatty acids - Oil – Yield - Premature ripening - Phoma macdonaldii- Soil tillage.
