|HOOKS, CERRUTI - University Of Maryland|
Submitted to: Nematology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/18/2016
Publication Date: 12/16/2016
Citation: Masler, E.P., Rogers, S.T., Hooks, C.R. 2016. Behavioral differences of Heterodera glycines and Meloidogyne incognita infective juveniles exposed to root extracts in vitro. Nematology. 19(2):175-183.
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 Because several chemical pesticides used to control nematodes have been withdrawn from use, growers face a critical need for the discovery of environmentally and economically sound nematode control agents. One approach to discovering new means of controlling nematodes is to identify ways to inhibit their metabolism and infectivity using naturally derived compounds. We discovered that soybean cyst nematodes and root knot nematodes respond differently to a series of natural plant root chemicals. These discoveries are significant because they reveal that plant molecules have significant potential as natural suppression agents since they affect the behaviors plant-parasitic nematodes need to survive. 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 in vitro behaviors of infective juveniles (J2) of Heterodera glycines and Meloidogyne incognita were compared in the presence and absence of plant root extracts. In an agar plate attraction-retention assay, H. glycines was 15-fold more responsive to a chemical attractant (CaCl2; P < 0.05) than was M. incognita. When an agar disc was placed on the agar surface, it induced aggregation of H. glycines at a rate 2.9-fold greater than M. incognita (P < 0.05). Crude extracts (slurries; 40 mg dry root weight ml-1 water) from roots of a series of plant species (corn, Zea mays; cucumber, Cucumis sativus; marigold, Tagetes patula; mustard, Sinapis alba; pepper, Capsicum annuum; soybean, Glycine max) differentially affected the two nematodes. Cucumber, marigold, pepper and soybean slurries each attracted H. glycines at rates between 2.2-fold and 3.6-fold over controls (P < 0.05). No root preparations were attractive to M. incognita, which were marginally but significantly (P < 0.05) repulsed by corn, cucumber, mustard and pepper, relative to controls. Preparation of selected root extract supernatants, which involved vacuum drying, decreased (P < 0.05) the attractiveness of marigold and soybean to H. glycines by 38 and 82 percent, respectively, but effect of pepper was unchanged. Supernatant processing had no effect on M. incognita behavior. Root supernatants from marigold, pepper and soybean at 1 mg dry root weight ml-1 water each decreased (P < 0.05) the frequency of head movement in both H. glycines and M. incognita relative to controls. However, dose responses were detected only with marigold, with maximum decreases (P < 0.05) in activity at 16 mg dry root weight ml-1 for each species. These decreases were significantly different (P < 0.05) at 46 and 66 percent, respectively, for H. glycines and M. incognita. The behaviors of the two nematodes were qualitatively different across in assays that required detection of signals across a short distance, whereas qualitative responses were similar where juveniles were immersed in treatment solution. In these assays, quantitative responses to marigold were different.