Phoma koolunga is one of three species that causes ascochyta blight (blackspot) of field pea (Pisum sativum L.) in Australia. Phoma koolunga was first described in 2009 from South Australian isolates and has since been reported in Western Australia, New South Wales and Victoria. However, the origin of the pathogen and its host range remain largely unknown. The aim of this study is to determine the host range of P. koolunga and to explore questions on the origin(s) of ascochyta blight pathogens in Australia.
Host range experiments were conducted on a selection of Australian native legumes and naturalised pasture species found in geographical proximity to field pea crops. One isolate of P. koolunga was used to spray-inoculate the range of legume species, including Pisum sativum cv. Kaspa as control. In the same experiment a different comparator isolate of P. koolunga was used to inoculate the same range of legumes. Control plants were mock-inoculated with water. The inoculated plants were placed in plastic humidity tents, one tent per isolate, in the same growth room. Disease severity will be measured as a percentage of leaf area diseased (%LAD) every 3 days up to 21 days post-inoculation. Disease incidence and percent leaf area diseased will be compared among isolates and species. Experiments are in progress and results will be presented.