Submitted to: Nematology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: April 2, 2008
Publication Date: November 1, 2008
Citation: Masler, E.P. 2008. Responses of Heterodera glycines and Meloidogyne incognita to exogenously applied biogenic amines. Nematology. 10:911-917. Interpretive Summary: Plant-parasitic nematodes attack all crops of agricultural importance, causing over $10 billion in losses annually to U.S. farmers. One problem facing growers is that environmental concerns will result in the elimination within the next few years of the most extensively used chemical used to kill nematodes in the United States. This loss makes the discovery of environmentally and economically sound replacement control agents critical. One approach to discovering new methods to control nematodes is to identify ways to disrupt their normal biochemical processes by using chemicals that occur naturally inside the nematode. We have discovered that small molecules called biogenic amines, which are produced naturally by nematodes, can be used to control hatching and movement in two species of plant-parasitic nematodes and that response to these amines is different in the two species. The discovery is significant because it identifies targets in plant parasites which can be used to control the nematodes. Consequently, this information will be used by researchers in the agrochemical and agricultural biotechnology industries who are developing safe, selective methods for nematode control.
Technical Abstract: Hatching and infective juvenile (J2) behavior in two species of plant-parasitic nematodes, Heterodera glycines and Meloidogyne incognita, were affected by in vitro treatment with the biogenic amines dopamine, octopamine, and serotonin. While the overall responses of each species to amine exposures were qualitatively similar, clear quantitative differences emerged. Dopamine reduced H. glycines hatch 66% at 40mM (P < .0001) but had no significant effect on M. incognita. Octopamine and serotonin each depressed hatching in each of the species, but H. glycines was more sensitive to treatment. 20mM octopamine reduced hatch by 57% (P < .0001) in H. glycines while 40mM octopamine reduced hatch by 39% (P < .0004) in M. incognita. Species differences in response to serotonin were more pronounced. Hatch was reduced 90% in H. glycines at 1mM (P < .0001) and 40% in M. incognita at 5mM (P < .0004). While hatching was generally depressed in all cases, infective juvenile behavior, as assessed by frequency of head movement, was strikingly different among the three amines. Dopamine had no effect on J2 movement in either species when assayed through 20mM, but did reduce frequency by 65% in H. glycines at 50mM (P < .002). Octopamine stimulated head movement in J2 of both nematodes but was strikingly more potent with M. incognita, with a maximum stimulation of 80% at 10mM (P < .0001) compared with 66% at 75mM (P < .0001) for H. glycines. ED50’s were 1.91mM and 32.35mM for M. incognita and H. glycines, respectively. Serotonin sharply depressed J2 head movement frequencies. 5mM reduced frequency by more than 80% in each species, and ED50’s were 0.73mM and 1.72mM serotonin for H. glycines and M. incognita, respectively.