Studies on in vitro effect of biological control agents against Colletotrichum gloeosporioides of papaya

The use of biological control agents as pathogen control agents has gained significance due to being non-hazardous to humans, biodegradable and environmentally friendly. The aim of the study was to test in vitro and in vivo antagonistic activity of yeasts and Bacillus spp. as biological control agents against Colletotrichum gloeosporioides of Carica papaya L. Isolation and in vitro bioassays of 45 yeasts and 55 Bacillus spp. against C. gloeosporioides were conducted on potato dextrose agar incubated at 25°C. The mycelial growth was measured in mm, seven days after inoculation and the percentage inhibition was calculated. Out of 100 biological control agents isolated from different plant parts of different hosts, 51 Bacillus isolates and 27 yeast isolates inhibited mycelial growth of C. gloeosporioides by a percentage above 50 during the in vitro primary screening. Bacillus spp. had more isolates that exhibited the strongest antagonistic activity and effectively inhibited the mycelial growth of C. gloeosporioides compared to yeast isolates. Twenty-one yeast isolates and 47 Bacillus spp. inhibited mycelial growth of C. gloeosporioides with a percentage greater than 50 during the in vitro secondary screening. This reduction was significantly different in comparison to the untreated control. Yeast isolates YCR3, YSY1 and Bacillus spp. BMR2 provided the best control of C. gloeosporioides. Bacillus spp. isolated and screened in this study showed to be more antagonistic against C. gloeosporioides compared to the yeast isolates in vitro.