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United States Department of Agriculture

Agricultural Research Service


item Gottwald, Timothy
item Trocine, T
item Timmer, L.

Submitted to: Phytopathology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/29/1997
Publication Date: N/A
Citation: N/A

Interpretive Summary: The device described in this manuscript was designed to study the spore release by fungal plant pathogens under various controlled environmental conditions. The device consists of a small environmental chamber into which specimens of plant material, infected with pathogens, can be placed. By the use of a computer, the environmental conditions within the chamber can be controlled and manipulated. The environmental factors that can be controlled are temperature, relative humidity, light in the visual and infra red range, simulated rainfall, wind speed, and vibration. Programs can be written on the computer to control all of the above parameters simultaneously, change them over time, and monitor and record the conditions within the chamber every few seconds. By studying each of these factors independently and in combination with other environmental factors, we hope to determine those conditions that cause the pathogens of citrus and other crops to release spores (infectious pathogens), and those conditions which inhibit spore release. The information can then be applied to assist in disease control in the field by changing horticultural practices to inhibit or delay pathogen release, or to cause release during times when the crop is not susceptible. Such a strategy forces the pathogen to shed its infectious propagules when no infection can take place, allowing the crop to escape infection, thereby protecting it.

Technical Abstract: An environmental chamber was designed to study aerial release of spores of ascomycetes and hyphomycetes, based on a previous device developed by C. M. Leach. Relative humidity (RH), temperature, red (660 nM) and infrared (880 nM) light, leaf wetness, wind speed, vibration, and rain events are controlled and monitored within the chamber via an RTC-HC11 real-time controller and data acquisition system. A BASIC computer program is uploaded to and controls the system by requesting a profile of environmental conditions that change through time according to user specifications. The controller interacts with a stepper motor, solenoids and relay switches via a feedback system based on data received from solid state RH, temperature, and leaf wetness sensors. The data acquisition system records environmental data from the chamber in RAM memory that can be downloaded to a PC for correlation with spore release data. Spores released from fungal specimens on plant tissues, and cultures that are placed into the chamber and subjected to the desired interactions of environmental conditions, are collected on a continuous volumetric spore trap at an exhaust port from the chamber. The device is presently being used to study Mycosphaerella citri and Alternaria citri spore release.

Last Modified: 10/17/2017
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