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Samira Bensmail, Fatma Halouane-Sahir, Sadjia Lahiani, Souhila Bensmail, Amel Bennacer, Samira Mebdoua, Abdenaceur Reghmit, Zahia Oukali

Abstract

The biocontrol of phytopathogens, including fungal parasites, is considered a natural and eco-friendly alternative to chemical treatments. This study aimed to isolate, screen, and identify rhizospheric fungal strains from durum wheat cultivated in central Algeria, along with endophytic fungi from wheat weeds in the same region, for their ability to produce chitinase, an enzyme relevant for biocontrol. Of the 61 fungal isolates, 37.7% showed varying levels of enzyme activity during primary screening on solid medium. The fifteen most productive strains were selected for secondary screening through submerged fermentation (SmF) using colloidal chitin as the substrate. The chitinase activity assay revealed that Aspergillus alliaceus PP235382 and Trichoderma harzianum PQ564478 were the most potent after 48 h (0.145±0.006 IU/mL) and 96 h (0.173±0.011 IU/mL) of incubation, respectively. Furthermore, both strains exhibited the highest antagonistic activity against three wheat pathogens (Fusarium graminearum, F. culmorum, and Alternaria alternata) in dual culture, with inhibition rates between 68.27% and 87.71%, among six fungal strains selected for their high chitinase activity. Chitinase production by T. harzianum and A. alliaceus under SmF conditions was enhanced to achieve 1.167±0.011 IU/mL and 0.915±0.033 IU/mL, respectively, using a mineral medium containing 1% (w/v) colloidal chitin and 1% (w/v) glucose under the same incubation time as previously determined. The crude enzymatic extracts of the antagonists provided the best inhibitory potential against F. culmorum. The two newly isolated strains and their chitinolytic extracts could be used to control wheat fungal pathogens.

Keywords

Rhizospheric fungi, Aspergillus alliaceus, Trichoderma harzianum, Chitinases, Biological control

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