Inhibitory Activity of Endophytic Fungi Isolated from a Philippine Local Variety of Adlai (Coix lacryma-jobi ‘Kibua’) Against Escherichia coli and Fusarium oxysporum f.sp. cubense Tropical Race 4

Inhibitory Activity of Endophytic Fungi Isolated from a Philippine Local Variety of Adlai (Coix lacryma-jobi ‘Kibua’) Against Escherichia coli and Fusarium oxysporum f.sp. cubense Tropical Race 4

 

Courtney Violeta [1,*] and Nanette Hope Sumaya [1,2]

 

[1] Department of Biological Sciences, Mindanao State University – Iligan Institute of Technology, 9200 Iligan City, Philippines

[2] FBL-Nematology Research Group, Premier Research Institute of Science and Mathematics, Mindanao State University-Iligan Institute of Technology, 9200 Iligan City, Philippines

*Email: courtneyvioleta@gmail.com

 

This study evaluated the in vitro inhibitory activity of fungal endophytes isolated from leaves, roots and kernels of Coix lacryma-jobi ‘Kibua’ against two known pathogens, Escherichia coli (strain ATCC 25922) and Fusarium oxysporum f.sp. cubense Tropical Race 4 (FocTR4). Agar plug bacterial assays for E.coli ATCC 25922 and dual culture assays for F. oxysporum f.sp. cubense Tropical Race 4 or FocTR4 were conducted to assess the antibacterial activity and inhibitory interactions, respectively. A total of 36 pure isolates were obtained from different parts of C. lacryma-jobi, with varying degrees of antagonism against FocTR4 and antibacterial activity against E. coli. Among the tested isolates, LF13 (29.33), KN14 (25.67), LF12 (25), LF9 (24.33), and LF8 (22.33) demonstrated the highest inhibitory activity against E. coli (values inputted are average ZOI of each isolates, unit mm), while KN6 (69.50%), LF13 (65.95%), KN7 (58.15%), LF12 (51.76%), and LF15 (50.36%) showed the most significant inhibitory activity against FocTR4 (values inputted are the inhibition percentage of isolates against the test fungal pathogen). For the antibacterial assay, 8 out of the 23 (34.78%) isolates that exhibited inhibition against the test pathogen exceeded the bacterial inhibition of the positive control Chloramphenicol, which further proves that E. coli developed resistance over time to the antibiotic. Statistical analysis confirmed the significance of the results, both in the antagonism and antibacterial assays. The findings highlight the potential of these fungal isolates as biocontrol agents and sources of novel bioactive compounds. Further investigations such as extraction of phyto- and mycochemicals of the plant and fungal isolates, and also microscopic and molecular identification of the said isolates through internal transcribed spacer regions of rDNA (ITS-rDNA) were recommended for further development of new novel compounds and mechanisms to combat against pathogens and for taxonomic verification of the fungi isolates extracted from the different parts of the Kibua variety of adlai.