Screening the Antibacterial Activities of Streptomyces Extracts against Phytopathogens Xanthomonas oryzae pathovar oryzae, Xanthomonas campestris pathovar vesicatoria, and Pectobacterium carotovorum pathovar carotovorum

Abstract

Xanthomonas oryzae pv. oryzae (Xoo), X. campestris pv. vesicatoria (Xcv), and Pectobacterium carotovorum pv. carotovorum (Pcc) are the causative agents of bacterial blight in rice, bacterial spot in pepper, and bacterial soft rot in carrot and cabbage, respectively. To isolate novel microbial extracts with antimicrobial activities against these bacteria, approximately 5,300 different Streptomyces extracts were prepared and tested. Microbial cultures from various Streptomyces strains isolated from the Jeju Island, Baekam, Mankyoung river, Jiri mountain etc. in Korea were extracted into three different factions -secreted hydrophobic, secreted hydrophilic, and mycelia- using ethyl acetate, water, and methanol. Initially, 34, 29, and 10 extracts were selected as having antibacterial activities against Xoo, Xcv, and Pcc, respectively. Extracts 1169G4, 1172E9, and 1172E10 had the highest growth inhibition activities against both Xoo and Xcv, and extracts 1151H7 and 1152H7 showed the highest growth inhibition activities against Pcc.