Results of a Department of Agriculture and Food project to identify the resistance and tolerance of crop cultivars to a local root lesion nematode were shared at the 2013 Agribusiness Crop Updates.
There are currently no economically viable chemical treatments available to control nematodes in broadacre agriculture in Western Australia, making crop rotation and variety selection the only effective tools to manage the pest in dryland cropping systems.
The department’s research, funded by the Grains Research and Development Corporation, confirmed growers can limit yield losses caused by Pratylenchus teres (RLN) by incorporating specific cultivars into their crop rotations.
Department research officer Sarah Collins said surveys demonstrate that several species of root lesion nematode (RLN) occur in WA and that one or more of these species occur in at least 60 per cent of Western Australian crop paddocks.
This equates to at vast 5.3 million hectares of the State’s cropping zone affected by the pest.
The surveys also found yield limiting levels of RLN in at least 40 per cent of WA crop paddocks.
Dr Collins said that Pratylenchus teres (P. teres), which is unique to WA, is capable of causing significant yield damage to a wide range of hosts.
“Average cereal yield losses due to root lesion nematodes of at least 5 per cent – and more often 10 to 15 per cent – are common for wheat and barley, and can rise as high as 75 per cent, particularly where P. teres is present,” Dr Collins said.
“Root lesion nematodes are microscopic migratory endoparasites that enter roots and feed on cell contents. They can continue feeding within the same root or move to feed on nearby root systems.
“This process damages root systems, leading to decreased water and nutrient uptake efficiency making the plants more susceptible to other stresses.”
Dr Collins said the research, incorporating both field testing and glasshouse trials, was aimed at identifying resistant crop and pasture species which limit the multiplication of P. teres in the soil by being poor or non-hosts of the pest or resistant cultivars.
“Resistance refers to the effect of the plant on the nematode where more resistant plants inhibit nematode reproduction and lead to declining nematode numbers,” Dr Collins said.
“Initial field testing of the resistance of 22 wheat, 21 barley and 12 canola cultivars to P. teres was carried out in Katanning in 2009 and 2010.
“Glasshouse trials enabled assessment of large numbers of wheat, barley, canola, pea and lupin cultivars in highly replicated trials.”
During the past two years, a tolerance trial was conducted near Toodyay to measure the effect of the nematode on plant growth and yield for 24 wheat varieties, with differences between varieties evident and greater yield losses occurring in less tolerant cultivars.
In this context, tolerance refers to the ability of a plant to limit yield loss despite the presence of nematodes within the soil.
“Our work characterising cultivar resistance and tolerance levels to P. teres will enable growers to select appropriate crop cultivars and species and develop effective rotational plans to minimise current and future yield losses,” Dr Collins said.
“Before applying that knowledge however, it is vital growers know which species of root lesion nematode is present in their crop because cultivars that are resistant to one nematode species may be susceptible to another.
“To determine nematode species and levels, growers should use available in-season testing services such as AGWEST Plant Laboratories. Several root lesion nematode species are identified through PreDicta-B™ soil testing, however currently P. teres is not reported by this test.”
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