|Sardanelli, Sandra - UNIV OF MARYLAND|
Submitted to: Nematology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: October 15, 2007
Publication Date: February 1, 2008
Citation: Masler, E.P., Donald, P.A., Sardanelli, S.S. 2008. Stability of Heterodera glycines (Tylenchida: Heteroderidae) juvenile hatching from eggs obtained from different sources of soybean, Glycine max. Nematology. 10(2):271-278. 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 used to kill nematodes 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 an experimental system that can be used to analyze hatching characteristics of the soybean cyst nematode, the most important pathogen of soybeans in the United States. This development is important because, for the first time, both external and internal factors that affect egg hatching can be detected and measured in a single experimental system. 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: The hatching behavior of Heterodera glycines eggs obtained from laboratory and greenhouse cultures and from the field was examined in vitro in tap water. Hatch of eggs from all cultures was robust, with up to 70 percent cumulative hatch at 2 weeks. Kinetics were similar, as hatching was linear in all cases from 3-10 days, slopes were 5.4-5.8 J2/day. However, cumulative percent hatch at 10 days varied from 45-68%. Eggs rinsed extensively in tap water had 39 percent and 25 percent lower hatch rates at 2 and 10 days, respectively, than did controls. Treatment of rinsed eggs with a tap water extract of non-egg cyst materials temporarily restored normal hatch level. Also, there was a positive correlation between egg density in hatch assays and percent hatch. Eggs obtained directly from the field hatched very poorly in tap water (0.7 J2/day) but were temporarily stimulated to hatch (3.5 J2/day) by tap water rinse. Field egg hatching behavior was lost after 2 generations in laboratory culture. Stability of H. glycines hatching kinetics and use of the hatching assay to examine egg dormancy and diapause are discussed.