S. CHAKRABORTY

CSIRO, Tropical Agriculture, St Lucia, Queensland, Australia

Abstract

Epidemiological research on anthracnose disease of stylo in Australia has improved understanding of the disease cycle through quantifying interaction between host, pathogen and the environment. Research has focused on: pathogenic and genetic variation in the Australian population of Colletotrichum gloeosporioides in comparison with diversity at the centre of origin for this pathogen in South America; environmental influences on anthracnose development and survival as a means to understand better the effectiveness of host resistance; and epidemiological consequences of strategies for the deployment of host-resistance genes. Through a close collaboration with breeding and cultivar development work, this research has helped to characterise and utilise better resistance for the management of anthracnose. Recently, a novel approach, using multivariate analysis, has been used to classify isolates into races taking into account the variation between pathogenicity assays. Both pathogenic and selection-neutral molecular markers have been used to reveal a limited range of variation in the Australian pathogen population compared with that at the centre of origin. This finding has important quarantine implications. The influence of weather factors in the dispersal, infection and survival of C. gloeosporioides has been established to characterise better the forms of genetic resistance which are prone to environmental variation. Evolutionary consequences of stylo genotype mixtures have been established to show that changes in race frequency can occur rapidly in the pathogen population, perhaps following changes in the composition of the host population due to outcrossing. As a model system, stylo anthracnose disease is being used to study the impact of predicted global climate change on plant diseases and the application of a 3-dimensional visual simulation model, 'virtual plant', to understand better the dynamics of disease and pest development within a plant canopy. An important feature of this research has been the effective national and international collaboration. With new opportunities for international research, this collaboration is expected to grow in strength and stature to help manage this important disease.