Characterization of Lysobacter spp. strains and their potential use as biocontrol agents against pear anthracnose.

Colletotrichum fructicola, is an important fungal pathogen that has been reported to cause pear (Pyrus) anthracnose in China, resulting in substantial economic losses due to severe defoliation and decreased fruit quality and yield. In the search for novel strategies to control pear anthracnose, Lysobacter strains have drawn a great deal of attention due to their high-level production of extracellular enzymes and bioactive metabolites. In the present study, we compared four Lysobacter strains including Lysobacter enzymogenes OH11, Lysobacter antibioticus OH13, Lysobacter gummosus OH17 and Lysobacter brunescens OH23 with respect to their characteristics and activity against pear anthracnose caused by C. fructicola. The results showed that the evaluated Lysobacter species presented various colony morphologies when cultured on different media and were proficient in producing protease, chitinase, cellulase and glucanase, with L. enzymogenes OH11 showing typical twitching motility. L. enzymogenes OH11 and L. gummosus OH17 showed potent activity against the tested fungi and oomycetes. L. gummosus OH17 produced HSAF (heat-stable antifungal factor) which was demonstrated to be a major antifungal factor in L. enzymogenes OH11 and C3. Furthermore, L. antibioticus OH13 and L. brunescens OH23 exhibited strong antibacterial activity, especially against Xanthomonas species. Cultures of L. enzymogenes OH11 protected pear against anthracnose caused by C. fructicola, and the in vivo results indicated that treatment with an L. enzymogenes OH11 culture could decrease the diameter of lesions in pears by 35 % and reduce the severity of rot symptoms compared to that observed in the control. In the present study, we systemically compared four Lysobacter strains and demonstrated that they have strong antagonistic activity against a range of pathogens, demonstrating their promise in the development of biological control agents.