Efficiency of Saccharothrix algeriensis NRRL B-24137 and its produced antifungal dithiolopyrrolones compounds to suppress fusarium oxysporum-induced wilt disease occurring in some cultivated crops
Résumé
Saccharothrix algeriensis NRRL B-24137 (SA) is a well-studied actinobacterium strain for its ability to produce numerous bioactive dithiolopyrrolone derivatives with appreciable antifungal properties. Our study aimed to investigate the possible usefulness of SA and its produced compounds to control several formae speciales of Fusarium oxysporum, which affect different important crops. Such is the case of F. oxysporum f. sp. lini (FOLi), F. oxysporum f. sp. lentis (FOLe), F. oxysporum f. sp. ciceris (FOC) and F. oxysporum f. sp. lycopersici (FOLy) which cause devastating wilt to flax, lentil, chickpea and tomato, respectively. Antagonistic properties of the strain SA have been primarily evaluated in vitro. This screening showed the significant antifusarium activity of the actinobacteria strain against FOLi, FOC, FOLe and FOLy. Consecutively, strain SA and FOLi soil development has been assessed. The SA soil treatment permitted an important decrease (threefold) in the FOLi infestation. Moreover, the actinobacteria soil density seemed maintained after 7-week treatment at an appreciable level of 44×106 CFU/gram of dry soil (gds). Through different pot experiments, soil pre-treatment with the SA strain significantly reduced the disease incidence of FOLi, FOLe, FOC and FOLy by 71.0, 73.3, 61.2 and 59.7%, respectively. However, the treatment with pure dithiolopyrrolones appeared less effective with about 50% of FOLi disease impact reduction, which thus suggested the involvement of more than direct antibiosis in the whole SA biocontrol performance. Globally, significant correlation between the in vitro antagonistic properties of SA and its capacity to reduce the disease occurrence (r=0.81, P≤0.05) has been highlighted.
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