Biological control of Botrytis cinerea in tomato and Fusarium graminearum in wheat using the novel species Burkholderia mycopellens and Burkholderia crassaminum

The antifungal activity of five novel Burkholderia strains against Botrytis cinerea R16 infection in tomato and Fusarium graminearum PH-1 infection in wheat was evaluated in vitro and in vivo. All strains reduced B. cinerea R16 infection symptoms in tomato as measured by chlorophyll fluorescence and chlorophyll index. The strains reduced the biomass accumulation of F. graminearum PH-1 on wheat leaves and helped preserve chlorophyll content, as indicated by a smaller reduction in the chlorophyll index in the Burkholderia-treated leaves as compared to the infected controls, highlighting their effective biocontrol activity. An evaluation of the phytotoxicity of the five strains revealed no effects on tomato, while for two strains, LMG 21824T and LMG 32019T, a negative effect on the chlorophyll fluorescence was observed in wheat, pointing to phytotoxicity. The whole genome sequence analyses of the five strains revealed a large number of biosynthetic gene clusters with fully conserved replicon position. Some of these, including gene cluster families encoding the production of occidiofungin A and the siderophores ornibactin and pyochelin, were shared by all strains, while others were variably present, yet their distribution did not provide a clear basis for explaining the observed phenotypic characteristics of these strains. Phylogenomic analyses demonstrated that these bacteria represented two novel Burkholderia cepacia complex species for which the names Burkholderia mycopellens sp. nov. and Burkholderia crassaminum sp. nov., are proposed.