BLACKLEG DISEASE ON OILSEED BRASSICA IN AUSTRALIA - A REVIEW

Blackleg, caused by the fungus Leptosphaeria maculans, is the major di sease of canola (Brassica napus) in Australia. The development of blac kleg-resistant B. napus varieties has been a major factor in the resur gence of the industry nationwide. The main sources of resistance used in Australian public breeding programs are Japanese spring varieties a nd French winter varieties. In these programs, all early generation ma terial is screened in field blackleg nurseries sown on, or adjacent to , infested canola stubble from the previous season. Little is known ab out the genetic control of resistance, and the mechanisms responsible for generating pathogenic variability oft. maculans isolates in Austra lia is Largely uncharacterised. Australian B. napus varieties are the most blackleg-resistant spring varieties in the world. Apart from grow ing blackleg-resistant varieties, other strategies that minimise infec tion and delay any breakdown in varietal resistance include growing ca nola on the same area only once every 3 years, destroying stubble, and eradicating volunteer plants between cropping seasons. Additionally, strategic use of chemicals can provide effective control to supplement varietal resistance in areas prone to severe blackleg infestation.