<i>Aspergillus</i>-<i>Penicillium</i> co-culture: An investigation of bioagents for controlling <i>Fusarium proliferatum</i>-induced basal rot in onion

Fungal co-culture is a method that allows the detection of interactions between fungi, enabling the examination of bioactive novel metabolites induction that may not be produced in monocultures. Worldwide, <i>Fusarium</i> basal rot is a primary limitation to onion yield, being caused by different <i>Fusarium</i> species. Current research directions encourage biological control of plant diseases as a replacement for routine chemical treatments. The current study aimed to investigate the co-culturing technique for mining new sources of bioagents that could be used as fungicides. <i>Aspergillus ochraceus</i> AUMC15539 was co-cultured with <i>Penicillium chrysogenum</i> AUMC15504, and their ethyl acetate extract was tested in vitro and in a greenhouse against <i>Fusarium proliferatum</i> AUMC15541. The results showed that <i>Aspergillus</i>-<i>Penicillium</i> (AP) co-culture extract significantly inhibited the growth of <i>F. proliferatum</i> with an MIC value of 0.78 mg/mL and showed antioxidant efficiency with an IC₅₀ value of 1.31 mg/mL. The brine shrimp toxicity testing showed a LC₅₀ value of 2.77 mg/mL. In addition, the co-culture extract showed the highest phenolic content at 114.71 GAE mg/g, with a 27.82 QE mg/g flavonoid content. Profiling of AP co-culture and its monoculture extracts by HPLC revealed a change in the metabolites profile in AP co-culture. Principal component analysis verified a positive correlation between the obtained HPLC data of <i>A. ochraceus</i> (A), <i>P. chrysogenum</i> (P), and AP extracts. Greenhouse experiments demonstrated that treating infected onion plants with the AP co-culture extract significantly enhanced all growth parameters. Additionally, the co-culture extract treatment resulted in the highest levels of total pigments (3.46 mg/g), carbohydrates (52.10 mg/g dry weight), proteins (131.44 mg/g), phenolics (41.66 GAE mg/g), and flavonoids (9.43 QE mg/g) compared with other treatments. This indicates a promising potential for fungal co-cultures in discovering new bioagents with antifungal properties and growth-promoting capabilities.