Caractérisation des Fusarium pathogènes de la tomate (Solanum lycopersicon) dans les agro-écosystèmes maraichers au Burkina Faso et stratégies de gestion intégrée
(2023)
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- Abstract
- Tomato production in Burkina Faso currently faces a number of constraints that prevent its full development. Of all the bio-aggressors affecting the sector, fungal diseases are a major contributor to the annual yield losses in market areas, due to the lack of knowledge of cryptogamic diseases on the part of growers and extension agents. The main objective of this work was to contribute to improving the sanitary quality and productivity of tomatoes in Burkina Faso by reducing the incidence of fungal pathogens in the soil. To this end, surveys were carried out in 2018, 2019 and 2020 at tomato production sites in 11 regions of the country and at the market to collect samples of diseased plants and seeds of available tomato varieties. A total of 226 samples of diseased plants and 14 tomato varieties were collected and analysed. The results of this diagnosis revealed several pathogenic fungi, the most important of which are Fusarium oxysporum, Fusarium equiseti, Macrophomina phaseolina, S. sclerotiorum and Athelia solani, Alternaria alternata and A. solani, Botrytis cinerea, Lasiodilodia theobromae, Fulva fulvia, Cercospora kikuchii and Colletotrichum truncatum. Plant wilt was the most frequently observed disease in all the agro-systems visited. Species of the genus Fusarium were the most abundant in all samples analysed, from which more than a hundred strains were isolated. Molecular characterisation of 92 strains by amplification of the elongation region using the specific primer pair TEF1 and TEF2 identified a diversity of species belonging to the genus Fusarium. According to the phylogenetic analysis, three species complexes were highlighted: the Fusarium oxysporum species complex (FOSC), composed mainly of 16 strains, the species F. languescens (syn. F. oxysporum f. sp. lycopersici), 3 strains of F. acutatum and two new taxa of 10 strains identified (in this study). Then the Fusarium solani species complex (FSSC), characterised by two strains of F. falciforme, and the Fusarium incanartun-equiseti species complex (FIESC), composed of the species F. incarnatum (12 strains), F. compactum (16 strains), F. duofalcatisporum (30), F. ipomoeae (01 strain), F. brevicaudatum (01 strain) and F. caatinguaense (01 strain). In fact, the pathogenicity test associated with the identification showed that, in addition to F. oxysporum (the well-known pathogen of tomato), these different species F. duofalcatisporum, F. incarnatum, F. compactum and F. falciforme were highly pathogenic, causing 100% damping-off (on seeds), crown and root rot and finally wilting of the plant (with severity ranging from 52.78% to 97.2%). Field diagnostic results showed that most growers have little knowledge of fungicides and control methods, and therefore use chemical molecules that are sometimes neither suitable nor registered. These synthetic products cannot guarantee effective treatment of the disease and also reduce the primary inoculum in the soil. To this end, this study developed control methods to combat wilt of tomato plants caused by telluric pathogens. Four plant extracts (Cymbopogon citratus, Ocimum basilicum, Syzygium aromaticum and Azadirachta indica) and the beneficial fungus Trichoderma harzianum (strain 8129) against Fusarium oxysporum, Meloidogyne incognita and their complex were evaluated in vitro, in the greenhouse and in the field. Under highly controlled conditions (in vitro), all plant extracts were highly toxic to nematodes (with 100% mortality after 24 and 48 hours of exposure) and completely inhibited (100%) the mycelial growth of C. citratus and S. aromaticum. T. harzianum significantly reduced both the nematode population (65% in 48h exposure) and fungal growth (67%). Of all the treatments applied in the greenhouse, S. aromaticum, A. indica and T. harzianum were the most effective against wilt caused by the complex (F. oxysporum/M. incognita). The nematicidal and antifungal properties of these two plants (S. aromaticum and A. indica) and of T. harzianum against the complex were confirmed by their application in the field. The susceptibility of eleven tomato varieties commonly grown in Burkina Faso to vascular wilt was then evaluated in the greenhouse and in the field. The varieties Raïssa and Jampack were resistant and the varieties Mongal, Cobra and FBT2 were tolerant to Fusarium head blight. Finally, the antagonistic activity of 7 bacterial strains from the Hauts Bassins and Cascades regions was determined using in vitro culture techniques under semi-controlled conditions. The application of these rhizobacteria as a soil treatment effectively reduced the activity of F. oxysporum in the soil and provided perfect protection for tomato plants. They also had a stimulating effect on the growth of the treated plants. These different results highlighted the existence of plant (S. aromaticum and A. indica) and microbial (T. harzianum) biopesticides of fungal or bacterial origin (rhizobacteria) which, in combination with resistant (Raïssa and Jampact) or tolerant (Cobra and Mongal) varieties and good cultural practices, could constitute a better management strategy against vascular wilt caused by F. oxysporum f. sp. lycopersici.
- Affiliations
UCLouvain SSH/IACS - Institute of Analysis of Change in Contemporary and Historical Societies UCLouvain SST/ELI - Earth and Life Institute
Citations
Tiendrebeogo, A. (2023). Caractérisation des Fusarium pathogènes de la tomate (Solanum lycopersicon) dans les agro-écosystèmes maraichers au Burkina Faso et stratégies de gestion intégrée. https://hdl.handle.net/2078.5/29737