Submitted to: Nematology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/18/2012
Publication Date: 1/8/2013
Citation: Masler, E.P., Rogers, S.T., Chitwood, D.J. 2013. Effects of catechins and low temperature on embryonic development and hatching in Heterodera glycines and Meloidogyne incognita. Nematology. 15(6):653-663. 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 Because several chemical pesticides used to control nematodes have been withdrawn from use, growers possess a critical need for the discovery of environmentally and economically sound nematode control agents.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 by using naturally derived compounds. We discovered that two plant-derived molecules called polyphenols inhibit hatch in the soybean cyst nematode and the root-knot nematode, two of the most important nematode pathogens of crops worldwide. We have also found that the more potent of these polyphenols also inhibited the activities of enzymes involved with hatching. These results are significant because they show that natural agents can potentially be used to protect 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: Mimics of two natural influences, a chemical similar to one present in cyst nematodes and low temperature exposure of nematode eggs, were evaluated for their effects on quantitative and qualitative features of embryonic development and hatching. The polyphenol epigallocatechin gallate (EGCG), an analog of a compound found in nematode cysts, reduced hatch from both Heterodera glycines and Meloidogyne incognita eggs. Reduction was by 22.7 % (P < 0.05) in H. glycines and 68.5 % (P < 0.05) in M. incognita at 14 days after exposure to 1.0 mM EGCG. Significant reductions (P < 0.05) in hatch were observed by 7 days after exposure in H. glycines eggs, and as early as 5 days in M. incognita. Half-maximal % hatch was delayed by 0.6 day in H. glycines and 1.1 days in M. incognita (16.2 and 18.3 %, respectively). Decreased hatch was associated primarily with an increase in un-hatched, but viable, J2. Hatch levels could be completely restored by Day 14 in both species, if EGCG was replaced with water on Day 3. Replacement on Day 7 partially restored hatch in M. incognita but was not effective in H. glycines. Inhibition of chitinase activity by EGCG suggests one factor in J2 retention in the egg. Exposure to low temperature decreased hatch by ca. 50 % in both species (P < 0.05), but without accumulation of un-hatched J2. This stage peaked at Day 3 in H. glycines treated eggs, and on Day 7 in M. incognita. However, response to low temperature in each species was characterized by developmental arrest at the J1 stage.