Large Incubation Chamber Suited for Use in Selection for Disease Resistance1

Abstract

The construction and operation of a large moist incubation chamber and its application in a disease resistance selection program are described. The walk‐in chamber is made of aluminum alloy sheeting bonded to urethane foam insulation. Inside dimensions are 3.36 ✕ 3.36 ✕ 2.05 m high, and it holds about 5,000 seedling alfalfa plants. The disadvantages of other incubation chambers, such as uneven moisture deposits, refrigeration failure, drying of leaf surfaces, small capacity, and high cost are reduced or eliminated by the simple design of this chamber. Temperature is controlled through the flow of thermal‐regulated water across the sloped floor of the chamber. Periodic misting along with the waterflow cooling system maintain the air at loo'% relative humidity. The chamber has been used successfully to produce leafspot and rust diseases of forage legumes and grasses. None of the pathogens required light for infection. In a selection program this chamber facilitates the production of a single disease whenever suitable plants are available, makes possible the sequential infection of regrowth with different pathogens, and reduces the number of escapes.