CONTROLLING PLANT-PARASITIC NEMATODES WITH NEMATODE-TRAPPING FUNGI AND ORGANIC

• Sponsoring Institution: National Institute of Food and Agriculture
• Project Status: COMPLETE
• Funding Source: HATCH
• Reporting Frequency: Annual
• Accession No.: 0207391
• Project Start Date: Oct 1, 2006
• Project End Date: Jun 30, 2007
• Program Code: [(N/A)]- (N/A)

Recipient Organization
UNIVERSITY OF CALIFORNIA, DAVIS
410 MRAK HALL
DAVIS,CA 95616-8671

Performing Department
NEMATOLOGY

Non Technical Summary
Plant-parasitic nematodes cause substantial damage to crops throughout California and the rest of the world. Farmers need new and safer methods for controlling these soilborne pests and one method is biological control, that is, control by natural enemies, including nematode-trapping fungi. Although nematode-trapping fungi occur naturally in nearly every soil, their numbers are usually too small to control plant-parasitic nematodes. This project will investigate factors that determine the ability of nematode-attacking fungi to control plant-parasitic nematodes in soil. Factors include: fungal-feeding nematodes (which may suppress the nematode-attacking fungi), bacterial-feeding nematodes (which may act as hosts and thereby increase the beneficial fungi); and organic amendments (which may support increases in the beneficial fungi). The project will also compare detection and quantification of the beneficial fungi using traditional vs molecular techniques.

Animal Health Component

50%

Research Effort Categories

Basic

50%

Applied

50%

Developmental

(N/A)

Classification

Knowledge Area (KA)	Subject of Investigation (SOI)	Field of Science (FOS)	Percent
215	1199	1120	50%
215	1499	1120	50%

Knowledge Area
215 - Biological Control of Pests Affecting Plants;

Subject Of Investigation
1499 - Vegetables, general/other; 1199 - Deciduous and small fruits, general/other;

Field Of Science
1120 - Nematology;

Keywords

biological control (nematodes)

nematode control

Goals / Objectives
1. Determine whether fungivorous nematodes limit control of pest nematodes by nematode-trapping fungi. 2. Determine which bacterivorous and fungivorous nematodes are and are not attacked by the nematode-trapping fungus Dactylellina haptotyla in soil amended with organic matter. 3. Determine which organic amendments/substrates most enhance nematode-trapping fungi and other natural enemies of nematodes. 4. Develop molecular techniques for detection and quantification of nematode-trapping fungi.

Project Methods
Soil microcosms will be used to determine which factors cause nematode-trapping fungi to increase or decrease in soil. Factors to be focused on include fungivorous nematodes, which may explain why nematode-trapping fungi sometimes decline when host nematodes are abundant; different species of bacterivorous nematodes, which may or may not be hosts for the fungi; and different kinds of organic amendments, which may support increases in the population densities and activities of nematode-trapping fungi. Molecular and conventional methods will be compared for the detection and quantification of nematode-trapping fungi.

Progress 10/01/06 to 09/30/11

Outputs
No outputs are reported for this period and this is a final report (the principal investigator retired on 28 June 2007).

Impacts
One of the most commonly studied nematophagous fungi, Arthrobotrys oligospora, increased to very large numbers when dead moth larvae were added to soil. The increase in population density, however, was not accompanied by an increase in nematode mortality as measured with assay nematodes. There was no evidence of negative feedback (density-dependent nematode mortality) on nematode population density. The results indicate that A. oligospora is unlikely to control plant-parasitic nematodes in agricultural fields. Detection of nematode-trapping fungi (Orbiliales) was compared with a culture-based method and with a molecular method (PCR using Orbiliales-specific primers). PCR failed to detect many species detected by the culture-based method and the culture-based method failed to detect many species detected by PCR. The results suggest that the two methods are complementary.

Publications

• Nguyen, V.L., J.L. Bastow, B.A. Jaffee, and D.R. Strong. 2007. Response of nematode-trapping fungi to organic substrates in a coastal grassland soil. Mycological Research 111:856-862.
• Jaffee, B.A. 2006. Interactions among a soil organic amendment, nematodes, and the nematode-trapping fungus Dactylellina candidum. Phytopathology, 96:1388-1396.
• Jaffee, B.A., J.L. Bastow, and D.R. Strong. 2007. Suppression of nematodes in a coastal grassland soil. Biology and Fertility of Soil 44:19-26.

Progress 10/01/06 to 06/30/07

Outputs
No outputs are reported for this period and this is a final report (the principal investigator retired on 28 June 2007).

Impacts
One of the most commonly studied nematophagous fungi, Arthrobotrys oligospora, increased to very large numbers when dead moth larvae were added to soil. The increase in population density, however, was not accompanied by an increase in nematode mortality as measured with assay nematodes. There was no evidence of negative feedback (density-dependent nematode mortality) on nematode population density. The results indicate that A. oligospora is unlikely to control plant-parasitic nematodes in agricultural fields. Detection of nematode-trapping fungi (Orbiliales) was compared with a culture-based method and with a molecular method (PCR using Orbiliales-specific primers). PCR failed to detect many species detected by the culture-based method and the culture-based method failed to detect many species detected by PCR. The results suggest that the two methods are complementary.

Publications

• Jaffee, B.A. 2006. Interactions among a soil organic amendment, nematodes, and the nematode-trapping fungus Dactylellina candidum. Phytopathology, 96:1388-1396.
• Jaffee, B.A., J.L. Bastow, and D.R. Strong. 2007. Suppression of nematodes in a coastal grassland soil. Biology and Fertility of Soil 44:19-26.
• Nguyen, V.L., J.L. Bastow, B.A. Jaffee, and D.R. Strong. 2007. Response of nematode-trapping fungi to organic substrates in a coastal grassland soil. Mycological Research 111:856-862.

Progress 01/01/06 to 12/31/06

Outputs
The effect of different organic inputs on nematode-trapping fungi in soil from the Bodega Marine Reserve was examined. The organic inputs included lupine leaf litter, grass leaf litter, dead isopods, dead moth larvae, deer feces, isopod feces, shrimp shells, and chitin. Inputs with lower carbon to nitrogen ratios (lupine leaf litter and dead isopods) caused the greatest increases in the nematode-trapping fungus Arthrobotrys oligospora. Primers for detecting nematode-trapping fungi were developed and compared with a traditional technique (sprinkle plates) for detecting nematode-trapping fungi. In initial tests, the primers detected some species detected by sprinkle plates, detected additional species undetected by sprinkle plates, and failed to detect some other species detected by sprinkle plates.

Impacts
Plant-parasitic nematodes can reduce crop production and alternative methods of control are needed. The current project should increase our understanding of how to enhance and detect some consumers of these pests.

Publications

• Jaffee 2006 No publication in this period.