Identification and characterization of the endophytic bacterium Bacillus atrophaeus XW2, antagonistic towards Colletotrichum gloeosporioides

Abstract

Bacillus atrophaeus XW2 was isolated from healthy poplar leaves and exhibited a strong inhibitory effect against Colletotrichum gloeosporioides, a predominant fungus causing poplar anthracnose. The culture filtrate and bacterial lysate of XW2 were antagonistic against hyphal growth and spore germination. The average diameter of the inhibition zones of hyphal growth were 22.3 mm for the culture filtrate and 12.1 mm for the bacterial lysate. The average inhibition rates of spore germination after 24 h were 94.6 % for the culture filtrate and 88.8 % for the bacterial lysate. In the presence of both culture extracts, hyphae developed vacuoles and swelling, and abnormalities were observed in 100 % of germinated spores. Lipopeptides isolated from culture filtrate and bacterial lysate had high antifungal activities against C. gloeosporioides. The average diameter of the inhibition zones were 23.2 mm for culture filtrate and 11.8 mm for bacterial lysate. Crude proteins isolated from culture filtrate and bacterial lysate also showed good inhibition qualities. The average diameters for the zones of inhibition were 22.3 mm for culture filtrate and 13.4 mm for bacterial lysate. Volatiles produced by XW2 inhibited hyphal growth of C. gloeosporioides by 60.2 % and were antagonistic against the germination of C. gloeosporioides spores after 3 days. Greenhouse studies revealed that XW2 had a 49.1 % efficacy in controlling poplar anthracnose 12 days after exposure to the pathogen. We consider that Bacillus atrophaeus XW2 is a promising natural biocontrol agent for use against C. gloeosporioides.