Factors affecting short and long distance dispersal of fungal pathogens - Chickpea Ascochyta blight as a model

Containment and eradication of exotic plant pathogens requires a comprehensive knowledge of epidemiology. Some fungal plant pathogens are spread by both rain-splash and wind, allowing dispersal over long distances and making containment difficult. Plant pathogens already identified in Australia with short and long distance dispersal are being used to evaluate a risk model designed for forecasting disease dispersal. Ascochyta rabiei, of world-wide significance in causing Ascochyta blight in chickpeas, has both rain-splash and wind dispersed spores, making it a suitable candidate to study the effect of environment on spore dispersal. Field trials were established in 2006 and in 2007 at two sites in south-eastern Australia to study the nature and pattern of spread of A. rabiei. Rain was critical in the initiation and continual spread of A. rabiei from diseased seedlings in 2006 and from chickpea residues in 2007. In plots of a susceptible cultivar, the prevailing wind was also influential in spread of disease from the central focus. Laboratory experiments to assess the effect of wind speed, rain droplet size and wind-driven-rain on spore dispersal, and studies on the factors affecting viability of conidia, will help to further calibrate the model. This model may provide a template for studying the spread of other diseases and for understanding likely scenarios of plant pathogen incursions.