Hatching Behavior in Heterodera glycines in Response to Low Temperature*

Abstract

Heterodera glycines eggs were exposed to low temperature (5°C) in the dark for various periods, and the effects of these treatments on hatching at 27°C were assessed. Low-temperature treatments caused a significant decrease in total percent egg hatch relative to untreated controls, but did not affect either the timing of egg hatch or the qualitative aspects of the hatch curve. Hatch curves comprised 3 distinct phases: hatch initiation (I), linear increase (II), and hatch rate decline (III). Hatch rates for all treatments were greatest during the first 12 d following hatch assay initiation, and rate decline occurred by day 14 regardless of treatment. Egg viability tests based upon vital staining demonstrated that refrigeration did not affect mortality, and monitoring progeny eggs obtained from plants inoculated with refrigerated eggs did not reveal any effect on hatching. Total percent hatch was directly dependent upon phase II linear increase rate. Depression of hatch by low temperature was not reversed when eggs were returned to 27°C. Results suggest that 1 or more developmental events were arrested, and that a diapause was induced.