Submitted to: Nematology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/1/2005
Publication Date: 9/1/2005
Citation: Masler, E.P., Zasada, I.A., Sardanelli, S. 2005. Manipulation of hatching behavior in heterodera glycines through exposure to low temperature. Journal of Nematology 37: 380. Interpretive Summary: Plant-parasitic nematodes are microscopic worms that 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 eliminate in a few years the most extensively used chemical for nematode control in the United States. These concerns make the discovery of environmentally and economically sound replacements critical. One approach is to discover natural targets in nematodes that can be used to develop novel control strategies. Egg hatching is one of the most critical parts of the nematode life cycle in agricultural fields, and is a prime natural target. In this paper we report the development of a novel experimental method for inhibiting egg hatching of the soybean cyst nematode, the most important pathogen of soybeans in the United States. This development is important because now, for the first time, it is possible to directly compare normal and inhibited eggs to help discover natural molecules that can prevent eggs from hatching. This will accelerate discovery of novel control molecules. This information will be used by researchers who are developing safe, selective and cutting-edge methods for nematode control.
Technical Abstract: Heterodera glycines eggs were exposed to low temperature (5°C) in the dark for varying periods, and the effects of these treatments on hatching were assessed. Low temperature caused a significant decrease in total percent egg hatch but did not affect hatch timing or the qualitative aspects of the hatch curve. The curve contained three key features: early hatch, initial hatch period, and sharp rate decline. Initial hatch rates for all treatments were highest during the first 12 days following hatch assay initiation, and declined markedly by day 14 in all cases. Direct and indirect measurements of egg viability demonstrated that treatments did not affect mortality, and the effects of treatment were not carried over to the next generation. Total percent hatch was directly dependent upon initial hatch rate. Depression of hatch by exposure to low temperature was not reversed when eggs were returned to normal rearing temperature, suggesting that development had been arrested. Effects of low temperature were observed in as little as 18 hours. Data suggest that one or more developmental events were arrested, and that diapause was induced.