Effet in vivo de biocontrôle d’un endophyte fongique sur l’atténuation des maladies phytopathogènes.

Abstract

This work investigates the potential of an endophytic fungus isolated from halophyte plants, evaluated as a biocontrol agent and plant growth promoter against two phytopathogenic fungi, on several host plants, under both in vitro and in vivo conditions. Endophytic fungi are a key component of the plant microbiome, capable of establishing mutualistic or neutral relationships with their host plants. In this study, we evaluated the biocontrol potential of an endophytic fungus of the genus Aspergillus sp., isolated from halophyte plants, against two phytopathogenic fungi Alternaria sp. and Diaporthe sp. on three host plants: cucumber (Cucumis sativus L.), mint (Mentha sp.) and the Mediterranean shrub Phillyrea latifolia, using in vitro and in vivo approaches. Direct confrontation assays on PDA medium demonstrated significant antagonism of Aspergillus sp. against both pathogens. Furthermore, the disc diffusion method revealed a weak activity of the crude extract, represented by inhibition halos not exceeding 14 mm. In vitro detached-leaf tests revealed contrasting responses depending on the host species: Phillyrea latifolia, a Mediterranean woody shrub with a thick cuticle and high secondary metabolite content, showed naturally high resistance to both pathogens, with very limited symptoms regardless of treatment. Mentha sp., by contrast, proved considerably more susceptible, and it was on this species that Aspergillus sp. exerted its most notable protective effect, particularly against Diaporthe sp., with a marked reduction in disease severity. The in vivo trial on cucumber confirmed a significant plant growthpromoting (PGPF) effect of Aspergillus sp., but did not demonstrate any reduction in pathogenic symptom severity. Co-inoculated plants even showed slightly higher severity than those infected by the pathogen alone, a result attributed to the seedbased inoculation route and the complexity of tripartite interactions under real conditions.