DAV00123 - Victorian Field Crop Nematology Project
In many Australian cropping soils the presence of nematodes limits field crop production. Murray and Brennan (2009 a and b) suggested that in south-eastern Australia alone, nematodes are reducing wheat and barley production by 4.9% ($98 million a year) and 5.1% ($42 million a year) respectively, with losses in excess of 20% possible. Field-crop nematology in south eastern Australia has been recently reviewed by Vanstone, Hollaway and Stirling (2008). In south-eastern Australia the nematodes of importance are the cereal cyst nematode (Heterodera avenae) and two species of root lesion nematode (Pratylenchus thornei and P. neglectus).
The nematode species and number present within a paddock can be efficiently determined using the DNA-based diagnostic test provided by SARDI (Ophel-Keller et al. 2008). Yield loss caused by nematodes is related to the density of the nematodes present in a paddock, so growers can minimise yield loss in two ways. The first is to grow crops or cultivars that are tolerant of the nematode (that is they can still yield well in the presence of the nematode). The second is to grow crops or cultivars that are resistant to the nematode and thereby reduce nematode densities; thus reducing losses in subsequent crops. For growers to select, and breeders to develop, field-crop cultivars with resistance and/or tolerance to the range of nematodes of importance in south-eastern Australia requires reliable field data.
Currently, in south-eastern Australia, there is limited information on the tolerance of cereal cultivars to the three nematodes of importance. The provision of tolerance ratings on newly-released cultivars will assist growers with the selection of cultivars that can minimise yield loss in the presence of medium to high nematode densities. Tolerance-screening trials can also provide data on the yield loss caused by different nematode densities, which can help growers and cereal breeders prioritise nematode-control strategies. Field experiments are required to determine the level of resistance to root lesion nematodes that is desirable within cultivars to prevent nematode densities increasing to damaging levels.
Breeders and growers currently do not have an understanding of the level of resistance that is desirable to maintain nematode densities below threshold levels in south-eastern Australia. Such information will inform strategies for molecular marker development and resistant-cultivar breeding.
Root- lesion nematodes have a wide host range that includes cereals, pulses and oilseeds. For growers to manage nematode densities within the cropping rotation they need to known the resistance/susceptibility of rotational crops. For most pulse crops the resistance/susceptibility to root-lesion nematodes has not been determined in more than 10 years (Hollaway et al. 2000, Taylor et al. 2000). To assist growers with root-lesion nematode management they need information on the resistance/susceptibility of new pulse varieties as part of the NVT process.
This project will provide information on the field tolerance and resistance of newly-released cultivars to the important nematodes that limit yield in south-eastern Australia. The project will also provide recommendations for target resistance levels for growers to maintain nematode levels in farming system below damaging levels.
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