Submitted to: Nematology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/29/2008
Publication Date: 7/1/2009
Citation: Zasada, I.A., Masler, E.P., Rogers, S.T., Halbrendt, J.M. 2009. Behavioral response of Meloidogyne incognita to benzyl isothiocyanate. Nematology. 11:603-610. 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 for controlling nematodes in the United States. This makes the discovery of environmentally and economically sound replacement control strategies critical. One approach to discovering new nematode control strategies is to identify ways to disrupt nematode development by using chemicals that occur naturally. We have discovered that a small molecule called benzyl isothiocyanate (BITC), which is produced naturally by plants, can be used to control plant-parasitic nematode movement and egg production, and that very small amounts of BITC nearly eliminate nematode parasitism on host plants. These results are significant because they demonstrate that low concentrations of BITC can be used to suppress plant-parasitic nematodes while minimizing effects on non-target organisms. This information will be used by scientists as they enhance the ability of plants that contain natural plant products to reduce plant-parasitic nematode damage to agricultural crops.
Technical Abstract: After the incorporation of brassicaceous plant material into soil, it is likely that nematodes are not always exposed to lethal concentrations of nematotoxic isothiocyanates. It would be informative to know what effect sub-lethal concentrations of isothiocyanates have on plant-parasitic nematode behavior and whether these concentrations play a role in nematode suppression. To address these questions, infective Meloidogyne incognita juvenile (J2) behavior was evaluated after in vitro exposure to sub-lethal concentrations of the secondary plant metabolite benzyl isothiocyanate (BITC). Behavior was qualitatively and quantitatively affected. Overall nematode activity, scored visually in treatment groups, and individual nematode movement frequencies quantified by video assay, were each significantly (P < 0.05) reduced within 2 hrs of exposure to 0.01 mM BITC. All responses were dose dependent through 0.03 mM BITC. Infectivity of BITC-treated M. incognita J2 on soybean (Glycine max) was measured directly by root staining and gall rating, and indirectly by egg production. All measures demonstrated significantly reduced (P < 0.05) infectivity after treatment of J2 with 0.01 mM BITC. In addition, egg production was almost completely eliminated (< 5% of control) by 0.03 mM BITC. The correlation between the effect of BITC concentrations on J2 activity and infectivity on subsequent egg production was positive (R2 = 0.54 and 0.63, respectively; P < 0.001), with decreased J2 activity and infectivity resulting in decreased egg production. BITC concentrations that do not cause mortality significantly affect M. incognita J2 behavior, indicating that sub-lethal concentrations can be used for nematode suppression.