ARS | Publication request: Root zone chemical ecology: Semiochemically mediated manipulations of nematode behavior

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: July 24, 2011
Publication Date: N/A

Technical Abstract: Tritrophic interactions among plants, pest and natural enemies of the pest have been thoroughly examined in the above-ground terrestrial environment. However, below ground interactions are still poorly understood. For example, some citrus root stock cultivars release volatiles in response to root weevil (Diaprepes abbreviatus) damage that attract entomopathogenic nematodes. Field experiments further revealed that many other nematodes, including plant parasitic, were attracted to volatiles from the insect damaged roots. Additionally, nematodes seem to integrate host signals as well as species specific signals. For instance, the root knot nematodes (Meloidogyne spp), the most economically important species, prefer uninfected over nematode infected roots when given a choice. Recently, the model nematode Caenorhabditis elegans, a bacterivorus nematode, has been shown to utilize pheromone communications. When crowded, or running out of food, C. elegans release dispersal pheromone(s) that trigger newly emerged nematodes to turn into an alternative developmental stage (dauer) where they preserve resources, stop feeding and start to search for a new food resource. Blends of similar pheromone components (called ascarosides) can initiate dauer, feeding, as well as sexual behavior. There is no return to the dauer stage after feeding behavior is initiated, thus without food the nematodes will die. We have strong indications that also entomopathogenic (Steinernema feltiaei) as well as plant pathogenic root knot nematodes (Meloidogyne spp) use similar pheromone communication. After an initial dispersal from a consumed host, if no food is found, both types of nematodes utilize infectious juvenile developmental states where they will slow down and wait. Pheromones and/or host (plant) attractants will trigger movement towards a perceived host and initiate feeding. So far, we have isolated and partially characterized the dispersal pheromone for S. feltiae. In summary, the nematodes might respond to unknown signals released by the infested roots but preliminary experiments indicate that root knot, and other plant parasitic nematodes, use pheromones to control behavior such as avoidance and dispersal. In this presentation we will present and discuss our progress towards utilizing host produced attractants as well as the nematodes own pheromones to manipulate the behavior of beneficial as well as plant pathogenic nematodes.