Diversity of Endophytic Fungi of Psidium guajava (Myrtaceae) and Their Antagonistic Activity against Two Banana Pathogens

Aims: The present study was carried out to determine the diversity of endophytic fungi that colonize the leaves of Psidium guajava, and to evaluate their antagonistic activity against Fusarium oxysporum f.sp. cubense and Mycosphaerella fijiensis which are the two main phytopathogens of banana plants.

Place and Duration of Study: The research was carried out at Microbiology Laboratory, Faculty of Sciences, University of Yaoundé I and Microbiology Laboratory, Faculty of Biotechnologies, University of Agronomic Sciences and Veterinary Medicine Bucharest, between April 2018 and February 2020.

Methodology: Fragments of surface sterilized leaves of Psidium guajava were inoculated on Potato Dextrose Agar supplemented with chloramphenicol. The isolated and purified endophytic fungi were identified based on their macroscopic and microscopic characters using a mycological atlas as guide. The non-sporulating isolates were identified by comparing the ITS regions of their DNA to those of known fungi registered in the GenBank database. The antagonistic activity of the endophytic fungi isolated against Fusarium oxysporum and Mycosphaerella fijiensis was screened using dual culture method.

Results: A total of 28 endophytic fungal were isolated from the leaves of Psidium guajava corresponding to a colonization frequency of 33.33%. These isolates were identified as: Aspergillus sp., Botryosphaeria sp., Fusarium sp., Neoscytalidium sp., Xylaria sp., Phyllosticta capitalensis, Cercospora apii, Xylaria longipes, Phomopsis sp., Phomopsis asparagi, Aspergillus versicolor, Pallidocercospora thailandica, and Xylaria grammica that belonged to the Deuteromycota and Ascomycota divisions. These endophytic fungi inhibited the growth of Fusarium oxysporum f.sp. cubense and Mycosphaerella fijiensis with the percentage inhibition varying respectively from 23.25% to 73.52% and from 21.36% to 100%. The species Botryosphaeria sp., Phomopsis sp., Phomopsis asparagi, and Xylaria longipes exhibited the greatest activity.

Conclusion: The leaves of Psidium guajava have a fairly varied diversity of endophytic fungi. These endophytic fungi can serve as potential biological control agents against Panama and Sigatoka diseases of banana and also would produce secondary metabolites with antifungal properties.