|Bonman, John - Mike|
Submitted to: Journal of Phytopathology
Publication Type: Abstract only
Publication Acceptance Date: 3/31/2006
Publication Date: 7/29/2006
Citation: Jackson, E.W., Chong, J., Avant, J.B., Bonman, J.M. 2006. Utilization of a detached leaf method for cereal rust disease studies.. Phytopathology S881. Interpretive Summary: A new laboratory technique was developed at the USDA ARS Small Grains and Potato Research Unit in Aberdeen, ID to eliminate contamination of cereal rust cultures when conducting experiments with these important pathogens. To develop the technique, detached oat leaves were suspended on special media in small plastic chambers and inoculated with the oat crown rust pathogen. Leaves in the sealed chambers were incubated in the laboratory and produced viable spores within 10 days. Using the technique we were able to identify resistant and susceptible oat cultivars. We were also able to produce viable spores of other cereal rust fungi, including the oat stem rust pathogen on oat leaves and wheat leaf rust pathogen on wheat leaves. The new technique provides an alternative means of maintaining pure cultures of infectious rust cultures for use in disease resistance research.
Technical Abstract: Cereal rust pathogens are obligate biotrophs with wind disseminated propagules and a large number of races. These characteristics make propagation of single-race cultures difficult in environments where multiple races are present. The objectives of this study were to develop an isolated propagation system using detached leaves and test the utility of the system to study host resistance. Oat leaves were cut into 10-cm sections, disinfested with 0.5% NaOCl for 5 min, and rinsed in sterile ddH<sub>2</sub>O. Leaf section were then suspended in sterile plastic boxes by enclosing 3.5 cm of each leaf section end between 4% agar blocks amended with various chemical constituents. The exposed 3-cm portions were inoculated in an aseptic hood with <i>P. coronata</i> urediniospores suspended in water. Boxes were sealed and incubated in a lighted growth cabinet at 21'C until sporulation. Viable spores were produced on leaves in all treatments except those with Auxin and the water agar checks. Using this method, detached leaves of 16 differential oat cultivars inoculated with two isolates showed the same reactions as whole plants screened under standard conditions in a growth chamber. Initial results with other cereal rust disease caused by <i>P. graminis f. sp. avenae</i>, and <i>P. triticina</i> indicate viable urediniospores can be produced on detached leaves of the respective host.