Using co-culture to enhance fungal biocontrol activity and photostability

Fungal co-culture is a method that has predominantly been used for the discovery and production of novel secondary metabolites not found in axenic culture. However, its potential to enhance fungal biomass fitness and to harness unique beneficial traits has received limited attention. In this study, two fungal isolates Penicillium sp. (F1) and Trichoderma sp. (F2), with beneficial attributes such as promoting plant growth and controlling plant pathogens, demonstrated compatibility when co-cultured on agar and on a semi-solid substrate based on oats. The combined biomass containing conidia from both fungi (Mix) and conidia from F2 alone were equally efficient at inhibiting the growth of four plant pathogens (Fusarium oxysporum, Rhizoctonia solani, Botrytis cinerea, and Sclerotinia sclerotiorum) in in-vitro competition assays. In an in-planta bioassay on tomato stems, the Mix caused a significantly higher reduction in disease severity (severity reduced by 60%) than the reduction caused by F2 (28%) and F1 (41%) individually. Biomass of the Mix also displayed better photostability when exposed to ultraviolet light UV-C, with no viability loss after 1 minute and 30% reduction after 5 minutes of irradiation. F2 and F1 significantly dropped viability by 4.7% and 7.5% after 1 minute and by 37% and 56% after 5 minutes of irradiation, respectively. This study demonstrates that the distinct traits of F1 and F2 can be exploited concomitantly when co-cultured, resulting in a combined biomass with greater abiotic stress tolerance and enhanced biocontrol activity. Further research is required to understand the mechanisms that underpinned the improved fitness of this fungal consortium.