Effects of cyst components and low temperature exposure of Heterodera glycines eggs on juvenile hatching in vitro

Authors: Masler, Edward; Rogers, Stephen

Submitted to: Nematology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/15/2010
Publication Date: 12/15/2010
Citation: Masler, E.P., Rogers, S.T. 2010. Effects of cyst components and low temperature exposure of Heterodera glycines eggs on juvenile hatching in vitro. Nematology. 13(7):837-844.

Interpretive Summary: Plant-parasitic nematodes attack all crops of agricultural importance, causing over $10 billion in losses annually to U.S. farmers. Because several chemical pesticides used to control nematodes have been withdrawn from use, growers possess a critical need for the discovery of environmentally and economically sound nematode control agents. One approach to discovering new ways to control nematodes is to identify ways to inhibit their infectivity and reproduction using naturally derived compounds and treatments. We have previously shown that short-term low temperature exposure of eggs from the soybean cyst nematode, the most important pathogen of soybean crops worldwide, results in long term suppression of hatching. We have now combined low temperature treatment with natural compounds derived from the female nematode to suppress hatch further. In addition to significantly reducing the number of infective nematodes, the combined treatments also disrupt the timing of hatch. This result is significant because it reflects a great decrease in the ability of nematodes to infect host plants when they are most susceptible to nematode attack. 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: The effects of low temperature treatment of Heterodera glycines eggs and the interaction of this treatment with egg condition and cyst influences were examined in vitro. Exposure of eggs to 5 C for 1 week followed by a return to normal culture temperature resulted in a 25-33 percent reduction in total cumulative percent hatch (P < 0.05) after 2 weeks at 28 C. There was no effect on the timing of hatch by low temperature. Hatch from encysted eggs was 40 percent lower(P < 0.05)than from free eggs at 2 weeks, and hatch from low temperature-encysted eggs was over 60 percent lower (P < 0.05) during the same period. In addition to depressed hatch, encystment altered the timing of hatch relative to free eggs from the same cohort. Hatch from free eggs in the presence of cyst contents was accelerated relative to free eggs without cyst contents, but the total cumulative percent hatch was not increased. Reduction in hatch as a result of low temperature treatment was significant (P < 0.05) only if the treatment was applied prior to the J1 stage. J1 were not affected relative to J2 hatch. However, the effect of low temperature on earlier stages was not detected until development ceased at early J1 and later J1 stages. Also, low temperature treatment affected the apparent locomotion of some newly hatched J2. 16-fold (P < 0.001) more J2 from treated eggs were retained on 30 micrometers pore sieves than those from control eggs. The depression of hatch by low temperature egg treatment was apparently the result of the residual effects on early embryo stages, leading to arrest of development prior to J2.