Diversité et pathogénicité de Fusarium spp. du blé dur dans la région de Sétif : tolérance variétale et biocontrôle par Saccharomyces cerevisiae

Abstract

. The objectives of this study were fivefold. First, to assess the occurrence and distribution of Fusarium spp. populations associated with durum wheat in the Sétif region (Northeastern Algeria) over two cropping seasons (2021–2022 and 2022–2023). Second, to identify and characterize the recovered Fusarium isolates. Third, to evaluate the pathogenicity and toxigenicity of these isolates. Fourth, to investigate the biocontrol potential of Saccharomyces cerevisiae against durum wheat Fusarium. Finally, to assess the varietal tolerance of local durum wheat varieties (Bousselam, Boutaleb, Oued Elbared, Mohamed Ben Bachir, Simeto, Vitron, Waha, and GTA Dur) and Italian varieties (Bullel and Svevo) to three Fusarium culmorum isolates through in vitro assays on Petri dishes, a growth chamber experiment for FCR evaluation, and a greenhouse experiment for FHB assessment. Survey results from 26 and 27 durum wheat fields during the two cropping seasons revealed disease prevalences of 19.23 % and 11.11 %, respectively. Identification and characterization of 23 isolates revealed notable species and biological diversity despite an overall moderate prevalence (15.1 %). Fusarium culmorum (13 isolates) was identified as the predominant species, followed by F. clavum (6 isolates), F. equiseti (2 isolates), F. algeriense (1 isolate), and F. proliferatum (1 isolate). Pathogenicity assays confirmed the prominent role of F. culmorum in fusariosis development, exhibiting the highest pathogenic and toxigenic potential through the production of the mycotoxins deoxynivalenol (DON) and zearalenone (ZEN). Other species (F. algeriense, F. clavum, F. equiseti, and F. proliferatum) displayed variable levels of pathogenicity and toxigenicity. The biocontrol potential of S. cerevisiae was evaluated through in vitro and growth chamber experiments. S. cerevisiae strains (SC1, SC2, and SC3) significantly inhibited the mycelial growth of F. culmorum (57.14 %, 57.53 %, and 53.57 %, respectively), reduced spore germination (18.61 %, 7.45 %, and 26.48 %, respectively), and mitigated disease severity (37.5 %, 50 %, et 25 % respectively), via direct mechanisms (mycelial interaction, chitinase and β-1,3-glucanase enzymatic activity) and indirect mechanisms (production of volatile compounds). Furthermore, yeast strains enhanced the growth of infected durum wheat plants by promoting stem elongation and root development through indole-3-acetic acid (IAA) production, phosphate solubilization, and siderophore secretion. Evaluation of the tolerance of the ten durum wheat varieties revealed significant variability across the different experimental assays. Bousselam and GTA Dur were identified as the most susceptible cultivars, whereas Bullel exhibited stable tolerance across all developmental stages.