Bioactivity of Some Endophytic Fungi from Cameroonian Medicinal Plants against Verticillium albo-atrum, Rhizoctonia carotae and Phytophthora megakarya

Abstract

Endophytic fungi (EFs) are beneficial microorganisms which grow in living plant tissues without causing any disease to their hosts. Most of them have antifungal properties. EFs of three herbaceous plants namely Lantana camara, Emilia coccinae and Bryophyllum pinnatum were isolated by using potato dextrose agar medium (PDA) and screened for their antifungal activity on the double direct confrontation (DDC) test on PDA. The growth diameter of pathogenic fungi with or without endophyte was measured weekly. Then, fourteen days after the DDC test, fungicidal or fungistatic activity of the EFs was assessed on the pathogens’ growth. Finally, EFs that strongly inhibited pathogens’ growth were submitted to the morphological characterization on PDA, Malt Extract Agar (MEA) and Sabouraud Dextrose Agar (SDA) media at three pH levels (5.2, 7 and 9). Results showed that eight EFs genera are associated with these herbaceous medicinal plants with diverse antifungal activities. EFs that significantly (p <0.05) inhibited the growth of the three pathogenic fungi were: Trichoderma harzianum (66%), Cercospora sp (58%) and Aspergillus sp (49%), 7 days after the DDC test. Endophytes T. harzianum and Cercospora sp were fungicidal on the three pathogens while Aspergillus sp was fungicidal on V. albo-atrum and R. carotae. There was a high morphological variability (colour, texture and pigments produced by EFs on culture media), and variability in their daily growth diameter and sporulation among EFs from one medium to another and from one pH level to another. This study suggests that T. harzianum and Cercospora sp endophytes possess the high antagonistic activity and can be used as an alternative to synthetic chemicals that control plant diseases