Dr Steve Marcroft1, Dr Angela Ven de Wouw, Dr Susie Sprague
1MGP, Horsham, Australia
Yield loss in Australia due to blackleg disease can be caused by crown canker resulting from infection during seedling growth, and/or upper canopy infection (UCI) from infection after the plant undergoes stem elongation. Currently, the Blackleg Rating system classifies cultivars for resistance to crown canker. The significant yield losses associated with UCI have only recently been quantified, with initial research directed towards understanding the risk factors such as flowering time, chemical control strategies and a robust assessment method which is complicated due to variability in symptom expression. A UCI rating system is required to enable growers to understand the level of susceptibility/resistance of each cultivar to inform crop management practices such as fungicide applications or isolation from stubble. Field screening for UCI resistance is problematic as cultivars differ in exposure to inoculum depending on their phenological development. Hence a controlled screening method is required to account for cultivar phenology, environment and pathogen genetic variability. Research under controlled conditions, whereby plants were inoculated at the same growth stage with single blackleg isolates, has identified both major gene and quantitative resistance. Germplasm is currently being screened to determine if the resistance is stable across environments (glasshouse, shadehouse, field) and blackleg populations (individual isolates, field populations). If successful we will have UCI resistance controls to allow comparison to all other germplasm. This may lead to the development of UCI blackleg ratings; however further work will be required to develop a cost effective high throughput system.
Steve has worked in the canola industry since 1994. He is responsible for applied research to support the canola industry.