Burkholderia isolates from a sand dune leaf litter display biocontrol activity against the bole rot disease of Agave sisalana

Abstract

Sisal (Agave sisalana) is an important source of biodegradable hard fiber for diverse industrial uses. The disease known as sisal bole rot leads to plant death and is caused by black aspergilli, including Aspergillus niger, A. brasiliensis and A. tubingensis. Bole rot is among the factors responsible for the decline of sisal production in Brazil. The potential of 16 Burkholderia sp. isolates obtained from sand dune leaf litter to control the disease was evaluated as part of a biocontrol program. The isolates of Burkholderia clustered in a new phylogenetic clade related to, but different from B. gladioli, B. plantari and B. glumae, its closest known relatives. All isolates secreted several enzymes, diffusible compounds, siderophores, volatile organic compounds (VOCs) and were able to solubilize phosphate, and inhibit mycelial growth and spore germination of Aspergillus niger in vitro. The Burkholderia isolates varied in their activity in vitro and in a greenhouse experiment, but consistently reduced disease severity by 54–77% in two independent field experiments. Because species of Burkholderia are opportunistic and might be pathogenic to plants and animals, the development of biocontrol products containing living cells of these bacteria has been viewed with care by regulatory agencies and scientists around the world. Future studies will focus on the development of products containing metabolites and heat-killed cells of these isolates to control sisal bole rot disease.