Isolation and characterization of a new Burkholderia pyrrocinia strain JK-SH007 as a potential biocontrol agent

Abstract

Poplar canker is a kind of serious disease of poplar branches in China and all over the world. In China, the poplar canker is mainly caused by three pathogens of Cytospora chrysosperma, Phomopsis macrospora and Fusicoccum aesculi, which is hard to control. A collection of 1,013 bacterial isolates obtained from the poplar stems in 9 regions of China. Of all the strains tested, 13 bacterial isolates inhibiting three pathogens (C. chrysosperma, P. macrospora and F. aesculi) growth were selected, whose inhibition zone width were more than 15 mm. Strain JK-SH007 exhibited the most obvious antagonistic activity. Besides, this strain also produced extracellular hydrolytic enzymes (β-1, 3-glucanases, proteases and chitinases). This bacterium had no pathogenicity and was identified as Burkholderia cepacia complex (Bcc) genomovar IX: B. pyrrocinia by the Biolog identification system combined with 16S rDNA and recA gene sequence analysis and morphological, physiological and biochemical methods characteristics. B. pyrrocinia JK-SH007 exhibited the highest biocontrol and colonization capabilities. After 3 months, plant height and ground diameter in poplar seedlings inoculated with JK-SH007 were significantly (P < 0.05) higher than in control (non-inoculated) plants. The selected B. cepacia isolate colonized poplar stems and leaves endophytically, promoting plant growth and suppressing pathogenic activities of C. chrysosperma, P. macrospora and F. aesculi on seedling of poplar. This is one of the few reports dealing with isolation and characterization of B. cepacia strains with biocontrol activity against the poplar canker. The endophytic isolate also has the potential to perform as plant growth promoter.