Assessment of sugarcane endophytic bacteria and rhizospheric Burkholderia species as antifungal agents

Naturally occurring bacterial endophytes were isolated from the stalks of six different sugarcane varieties. The highest numbers of bacterial populations were isolated from variety N12 and this variety was used for further investigations. Xylem sap as well as crushed cane sap was used for isolations, but no differences were observed between the type and numbers of species isolated. Endophytic bacterial populations decreased from the lowest to the upper-most internode. The lowest internode was surface sterilized and used to extract bacterial species on four different media (modified PW, TSA, PCAT and Candida medium). Most bacterial species were isolated on PW while PCAT medium was used to isolate Burkholderia and Pseudomonas species. The most common bacterial species isolated from sugarcane stalks were Pseudomonas spp., Zymomonas spp., Burkholderia spp., Bacillus spp., Serratia spp., Klebsiella spp. and Xanthomonas spp. Burkholderia reference strains, local endophytic stalk isolates as well as local Burkholderia isolates from the sugarcane rhizosphere were tested for their antifungal activity against sugarcane smut (Ustilago scitaminea)and Fusarium spp. causing stalk rot. Forty-seven strains inhibited the growth of Ustilago while seventy-two strains inhibited the growth of Fusarium in vitro. Twenty-one of these bacterial strains inhibited the growth of both Fusarium and Ustilago.