Models of sugarcane smut disease and their implications for testing variety resistance.
The testing procedure currently used for assessing Ustilago scitaminea resistance in sugarcane varieties is empirical and leads to anomalies. Models for between crop changes in infection rate are proposed, based on the resistance mechanisms of plants to the disease. The probability of infection of a bud is modelled as 1-(1-p)\sup\s, where s is the number of smut spores reaching sites of infection and p is probability of any one of them causing an infection. The models have implications for variety resistance trials and suggest modifications of testing procedures which may lead to more effective ways of selecting resistant varieties for commercial use.