Role of Pseudomonas Produced Hydrogen Cyanide in Biological Control of Plant-parasitic Nematodes

Plant-parasitic nematodes are among the most devastating pests world-wide, causing extensive damage to important agriculture crops. The management of nematodes is challenging. Current methods used for nematode control rely mostly on using chemical nematicides and naturally resistant plants. Because of serious health and environmental problems associated with chemical control and over use of resistant plants resulting in resistant breaking strains of nematodes, alternative nematode-control methods are needed. Several potential nematode-biocontrol agents, including bacteria and fungi, have been studied for their antagonistic effect toward plant-parasitic nematodes. However, a concise picture about the biological agent’s mechanisms used to antagonize nematodes remains elusive. In the present study, over 60 different isolates of Pseudomonas were identified that were lethal to the free-living nematode, Caenorhabditis elegans. All nematodelethal isolates of Pseudomonas were genetically, phenotypically, and biochemically characterized for their motility, exoprotease activity, and production of siderophores, polysaccharides, and secondary metabolites (cyanide, DAPG, PCA, pyrrolnitrin and pyoluteorin). These Pseudomonas strains were also screened for biocontrol activity against plant-parasitic nematodes (Meloidogyne incognita and Heterodera glycines), plant-pathogenic bacteria (Agrobacterium rhizogenes) and fungi (Fusarium solani). From our phenotypic characterization, one of the most common traits to most of the nematode-lethal stains was production of cyanide. Cyanide production was found in 87% of the C. elegans-lethal strains and 100% of the plant-parasitic nematode lethal strains