Key points

• Cereal varieties with resistance and tolerance to cereal cyst nematode and root lesion nematode are an important part of an effective management package
• Genetic sources from West Asia and North Africa have been identified and packaged into locally adapted germplasm for wheat

The development of resistant and tolerant varieties is essential for on-farm management of cereal cyst nematodes and root lesion nematodes.

To better understand and ultimately defeat soil-borne nematodes, including cereal cyst nematodes (CCN) and root lesion nematodes (RLN), GRDC has invested in two five-year research projects looking at management strategies and breeding.

The research is led by the University of Southern Queensland and the University of Adelaide, in conjunction with the South Australian Research and Development Institute (SARDI).

New strategies for nematode control have already reduced costs to the Australian grains industry. These strategies integrate:

• diagnosis of nematode population densities in individual paddocks;
• growing cereal varieties with resistance (the ability of a plant to reduce nematode reproduction in its roots) and/or tolerance (the ability to yield well despite infection); and
• rotation with resistant crop species.

Root lesion nematodes

For RLN, significant progress has been made, but substantial losses still occur in the northern region, especially from Pratylenchus thornei. The most effective way to minimise these is through development and deployment of improved varieties.

To support this breeding effort, we identified sources of P. thornei resistance in genetically diverse collections of wheat, developed mapping populations and mapped quantitative trait loci (QTL) on chromosomes 2B, 6D and 7B. For one source of resistance, we recently fine-mapped a resistance gene to a very small region of chromosome 6D.

For P. thornei tolerance, we used the commercial varieties EGA Wylie and EGA Gregory as sources of tolerance and mapped QTL on chromosomes 3B and 6D, respectively. Importantly, the tolerance and resistance QTL on 6D are at distinct positions on that chromosome, indicating they are distinct genetic traits and both must be incorporated into varieties to optimise on-farm management.

As most of the sources of P. thornei resistance for wheat were ‘exotic’ – synthetic hexaploid wheats and materials from the West Asia and North Africa (WANA) region – we undertook pre-breeding to ‘package’ resistance and tolerance genes into adapted backgrounds. After repeated selection for RLN resistance and tolerance, 19 improved lines and numerous DNA markers have been delivered to Australian plant breeders.

One of the challenges in controlling RLN is that they have wide host ranges and can infect more than one crop in farming systems. To support breeding for RLN control throughout rotations, we have also mapped resistance in barley and chickpeas and have developed DNA markers that can be used by breeders of those crops.

Cereal cyst nematodes

CCN once caused devastating damage to cereal crops in the southern region, but has been largely brought under control, thanks to growers adopting resistant varieties and appropriate crop rotation practices. The DNA markers developed in these projects will assist cereal breeders with selection of resistant germplasm.

In our research on CCN, we are closing in on specific genes that determine resistance: Rha2 and Rha4 in barley and Cre8 in wheat. This work is providing new insights into how nematodes harm plants and how resistance genes counteract this.

More information: Jason Sheedy, 07 4631 1185, jason.sheedy@usq.edu.au; Professor Diane Mather, 08 8313 7156, diane.mather@adelaide.edu.au