Ground Cover Supplement : GC Supplement - Oilseed breeding
13 OILSEED BREEDING GROUND COVER CANOLA Table 1 The relationship between blackleg severity when the same canola variety is sown into its own stubble compared to sowing into the stubble of a different canola variety, illustrating how management decisions can modify disease risk Plants sown in 2008 into canola stubble Stubble source of varieties sown in 2007 Trial 45Y77 ATR BeaconA AV-GarnetA Blackleg severity (per cent) 45Y77 53 33 37 Pot experiment -- Nurcoung, Victoria ATR BeaconA 35 52 34 Field trial -- Kalkee, Victoria AV-GarnetA 23 12 61 Field trial -- Nurcoung, Victoria BLACKLEG SEVERITY VARIES depending on regional climate and intensity of canola production. Currently, blanket control recommendations focus on: nplanting canola varieties with a high level of genetic resistance; n avoiding canola stubble; and nusing a seed dressing or fungicide-amended fertiliser. By developing a rating system for risk factors we aim to provide growers with the ability to quantify disease risk and to establish how this risk can be modified by changes in management. The risk of blackleg is influenced by: nannual rainfall and how much of this falls in autumn; ntime of sowing; nthe proportion of the farm sown to canola; nvariety resistance rating; nthe use of a fungicide on the seed or fertiliser; nthe distance from stubble of different or the same variety; and nhow many years a variety has been sown on the farm. Each risk factor can be rated. For example, an annual rainfall of 500 millimetres could be rated '8' compared to '5' for areas receiving only 400mm. Some factors are within the control of growers and others cannot be influenced. However, by assigning a rating to each risk factor a total risk can be quantified prior to sowing. A total risk value would help growers understand how different risk factors interact and what impact a management choice could have on to the potential disease risk (Table 1). The more difficult part of the risk assessment process is for the canola industry to determine what constitutes a low, medium or high-risk situation. The system currently being explored bases the score for each factor on current knowledge, however each score is subjective and will change as more information becomes available. Even once this hurdle has been overcome, the score provides only a snapshot of risk at the start of the season. Climatic conditions during the growing season and changing virulence of the blackleg pathogen can modify the risk of blackleg occurring. To keep the system up to date, a process of monitoring support is proposed. Such support could include collecting and disseminating information about disease incidence and severity at regional National Variety Trials yield sites, and trapping spores and using a rapid DNA analysis to determine the frequency and virulence of those spores. A similar practice is being tested for windborne spores of pulse diseases. While the three current control methods will EACH RISK FACTOR CAN BE RATED. Paddock-based risk assessment for blackleg remain central to the management of blackleg, the introduction of a paddock risk assessment would help inform growers of the relative importance of each method for specific paddocks. The Canola Association of Australia's blackleg ratings and information on managing the risk of blackleg in canola can be found on the GRDC website (www.grdc.com.au) and on the Agronomy Centre section of the Australian Oilseeds Federation website (www.australianoilseeds.com/agronomy_centre). □ GRDC Research Code UM00030 More information: Dr Steve Marcroft, consultant, Marcroft Grains Pathology, 03 5381 2294, email@example.com Blanket recommendations for blackleg can overlook specific paddock risks By Steve Marcroft The factors promoting blackleg interact so rather than blanket recommendations a paddock-by-paddock assessment of risk is being developed.
GC Supplement - Climate
GC Supplement - Pulse breeding