In vitro Evaluation of Burkholderia ambifaria for the Biological Control of Major Postharvest Fungal Pathogens in Citrus Fruits

Postharvest fungal diseases in mandarin fruits cause significant economic and nutritional losses during transport and storage. The control of postharvest diseases in citrus fruit involves frequent and large amounts of chemical fungicides. Increasing concerns about health hazards and environmental pollution caused by the use of chemicals have necessitated the development and use of environmentally friendly control strategies as an alternative to chemicals for the control of post-harvest diseases in citrus fruits. The bacterial isolates as biological control agents (BCAs) are one of the most suitable alternatives to synthetic fungicides, which are banned or restricted for use in post-harvest disease management. Fungal diseases such as black mould (Aspergillus niger), blue mould (Penicillium italicum), green mould (Penicillium digitatum), sour rot (Geotrichum citri-aurantii), and anthracnose (Colletotrichum gloeosporioides) cause the most significant postharvest losses in citrus fruit. The BCA bacterial isolate used in this study was isolated from healthy mandarins and identified as Burkholderia ambifaria by Matrix Assisted Laser Desorption Ionisation Time of Flight-Mass Spectrometry (MALDI TOF MS; MicroFlex LT, Bruker Daltonics, Bremen, Germany) analysis. In this study, the antagonistic activity of B. ambifaria on the inhibition of mycelial growth of A niger, P. italicum, P. digitatum, G. citri-aurantii and C. gloeosporioides isolated from mandarin fruits was determined under in vitro conditions. In dual culture tests, the BCA B. ambifaria isolate inhibited the mycelial growth of C. gloeosporioides by 66.67%, A. niger by 69.40%, G. citri-aurantii by 73.33%, P. italicum and P. digitatum by 77.78%. The high level of antagonistic activity of the bacterial isolate in inhibiting the mycelial growth of fungal pathogens showed that B. ambifaria has the potential to be used as a BCA against diseases occurring during post-harvest storage.