Cassava Endophytic Bacteriome as Potential Biocontrol Agents Against Three Crop Phytopathogenic Fungi

Crop yield losses stemming from pathogen infection and pests constitute 10%-40% of the potential annual total world crop production. Biological control agents have gained prominence as an environmentally friendly alternative to the use of hazardous synthetic agrochemicals. Herein, we evaluated the potential role of endophytic bacteria from cassava as biological control agents of three crop phytopathogenic fungi. Eighty-four endophytic bacteria isolated from cassava were assessed for antagonistic activity against phytopathogens Colletotrichum siamense, Colletotrichum sublineola, and Phytophthora infestans infecting cassava, sorghum and potato, respectively. Fourteen endophytic bacteria exhibited antifungal activity against the three phytopathogens. Of the 14 endophytic bacteria, four [Bacillus siamensis AS3, B. velezensis (DP1 and CS3b) and B. subtilis DL6] demonstrated significantly high inhibition rate on mycelial growth ranging from 62% to 72.3% against C. siamense, 63%-65.9% against C. sublineola and 64%-75.3% against P. infestans as compared with the control. The four endophytic bacteria produced volatile organic compounds that inhibited fungal growth ranging from 34.1% to 46.4% in P. infestans, 31.9%-36% in C. siamense and 33.9%-39.6% in C. sublineola. The results highlight the biocontrol potential of endophytic bacteria from cassava against three crop phytopathogenic fungi, which could be used for the future development of sustainable management strategies using environmentally friendly approaches. This study demonstrated that B. siamensis, B. velezensis, and B. subtilis with a strong antagonistic effect on C. siamense, C. sublineola, and P. infestans, can be potential biocontrol agents for cassava and sorghum anthracnose and potato late blight.