Incidence and severity of blackleg caused by Leptosphaeria spp. in juncea canola (Brassica juncea L.) in Australia

Abstract

Juncea canola (Brassica juncea L.) is being developed throughout the worlds canola growing countries as a drought tolerant, shatter resistant and highly blackleg resistant option to canola (Brassica napus L.). Juncea canola was grown commercially in Australia for the first time in 2007. This study determined the incidence and severity of blackleg infection in juncea canola prior to commercial release throughout south-eastern Australia in 2006 and 2007, and then again 5 years after commercialisation (2010–2013) to determine if blackleg severity had increased. Blackleg was found at all 127 sites surveyed throughout Victoria, New South Wales, South Australia and Western Australia. The severity of blackleg infection differed among sites and among the juncea canola cultivars and breeding lines suggesting that differences in resistance may be present. This is the first report that L. maculans isolates virulent on B. juncea are already widespread throughout the Australian canola growing regions and contradicts the widespread opinion that B. juncea is immune to blackleg. This also demonstrates that blackleg infection was already occurring in juncea canola prior to commercialisation of this crop in Australia and that disease management strategies similar to those used in canola cultivation will need to be implemented.