Low-molecular-weight metabolites produced by Pseudomonas aeruginosa as an alternative to control Huanglongbing in Citrus sinensis cv. Valencia

Abstract

Huanglongbing (HLB) is the most destructive disease of citrus worldwide and an efficient management strategy to control it has not yet been established. The potential of pseudomonads to suppress plant pathogens is well known and the secondary metabolites they produce represent new alternatives of compounds to control plant diseases. The main challenge is to find new compounds that show strong antibiotic activity, low toxicity to plants and little or no harm to the environment. The objectives of the present study were to determine the potential of the F4A fraction from Pseudomonas aeruginosa to control HLB and to induce systemic resistance. Low molecular weight compounds with antimicrobial activity were purified with organic solvent, thin layer chromatography (TLC) and normal and reverse phase chromatography. Compounds present in the F4A fraction were mainly obtained by thin-layer chromatography (TLC) and Preparative-High Performance Liquid Chromatography (HPLC-prep). To assess their biological activities, conventional and quantitative polymerase chain reaction were usxed. The F4A was sprayed on citrus trees infected with the causal agent of HLB, ‘Candidatus Liberibacter asiaticus’ under greenhouse conditions. The bacterial titers were reduced and defense genes were induced in leaves of trees treated with F4A, as assed by PCR analysis. The results showed that F4A (pseudomonads secondary metabolites) may provide a useful tool for the management of HLB.