Studies into races of sugarcane rust
A technique was developed for testing for physiological races of sugarcane rust. A range of cultivars were inoculated with a single spore isolate of Puccinia melanocephala by discharging 3 mg of urediospores into a spore settling tower by compressed air at 200 kPa pressure for one second with a settling time of ten minutes. A range of reaction types were obtained using this method. These reaction types were similar to reactions on naturally infected field grown plants. Components of stable resistance such as generation time, uredia number per mm2 and uredia diameter were also evaluated. The more resistant cultivars had fewer uredia per mm2 compared to the susceptible cultivars. No difference was recorded in generation times and size of uredia. The age of the leaf inoculated (between 24 and 75 days) did not have any apparent effect on host reaction type, generation time, uredia number and uredia size.