Submitted to: Journal of Nematology
Publication Type: Abstract Only
Publication Acceptance Date: April 13, 2005
Publication Date: October 31, 2005
Citation: Masler, E.P., Zasada, I.A., Sardanelli, S. 2005. Manipulation of hatching behavior in Heterodera glycines through exposure to low temperature [abstract]. Journal of Nematology. 37:380.
We have previously shown that laboratory cultures of Heterodera glycines produced eggs that segregated into two groups defined by hatching behavior. Group I eggs readily hatched in water (27 degrees C) in a linear pattern through 12 days, with 60 to 70 total percent hatch (TPH). Group II eggs, the 30 to 40% that did not hatch in water, hatched when exposed to soybean plants; these eggs resembled H. glycines eggs collected from the field in hatching behavior. Physiological differences between Group I and II eggs can provide a means to investigate developmental and hatching mechanisms in this species. In initial experiments, we used refrigeration (5 degrees C) to mimic one environmental parameter encountered in the field. Refrigerated eggs, subsequently returned to 27 degrees C, exhibited decreased TPH with increased refrigeration length (e.g., ~70 TPH, no refrigeration; 30 TPH after 2 weeks refrigeration, 20 TPH after 4 weeks, <10 TPH after 6 weeks). Regardless of refrigeration length hatch rates were linear through 12 days, hatch curves had similar shapes, and mortality was the same for both non-refrigerated control eggs and refrigerated groups. Eggs refrigerated for more than 8 weeks did not hatch in water, but did hatch when exposed to soybean plants. We argue that refrigeration affects one or more critical stages in embryogenesis, and that developmental pathways that render the pre-infective juvenile ready to hatch were arrested. This developmental arrest was overcome by some outside stimuli (e.g., host plant) but not by others (e.g., temperature). Data are provided to illustrate the effect of refrigeration on hatching kinetics, and models are presented for investigating the developmental mechanisms affected.