Ancient wheat on the road to resistance
Wild, ancient wheat grasses, the ancestors of modern wheat varieties, are becoming essential to varietal breeding. Although now on the verge of extinction, scientists believe these ancestors hold a vital key to solving Australia’s problem of root-lesion nematodes.
Root-lesion nematodes (RLN) are considered most likely endemic to the Fertile Crescent region in the Middle East where wheat originated some 8,000 years BCE. From there, RLN probably spread around the world with grain cultivation across North Africa, Europe, America, and finally Australia.
Scientists believe Australian wheat varieties were selected initially in the absence of RLN. This has resulted in new varieties being susceptible, losing the resistance that their wild ancestors once had.
Currently, no commercial wheat varieties are resistant to the ravages of RLN, and the massive yield losses growers experience each year are of great concern to the industry. The species Pratylenchus thornei is the most prevalent in northern grain-growing systems, and can cause up to 70 per cent yield loss in susceptible wheat crops.
Considering the urgency, wheat researchers at Queensland's Department of Agriculture and Fisheries (DAF) were excited to discover that ancestral wheat species, and 'landraces' (indigenous wheats cultivated in ancient villages), appear to be resistant to P. thornei.
“We realised the resistances that aren't available in commercial wheats, do exist in their ancient ancestors,” says Professor John Thompson, Crop Nematologist at University of Southern Queensland’ who supervises the GRDC-funded wheat pre-breeding program into genetic options for RLN control.
“Our glasshouse experiments found a number of wild varieties had resistance to P. thornei,” he says. “So we selected the best ones of these, and are now working to cross their resistances into adapted wheat varieties for the northern region, and for Australia generally.”
Developing adapted germplasm with resistance to both species of RLN (P. thornei and P. neglectus) is the research team’s ultimate aim.
“Tolerant varieties can still yield well, but growing them doesn’t fix the nematode problem,” explains Professor Thompson.
“Tolerant plants remain susceptible, and nematodes will continue to multiply inside their roots. A resistant variety, however, will prevent build-up of nematode populations quite dramatically and ultimately reduce populations of nematodes in paddocks,” he says.
“We now have valuable sources of resistance and established screening methods to select progeny for resistance, and eventually develop commercially available resistant varieties” he says.
“The current problems with P. thornei in northern region paddocks will be substantially reduced when most wheat varieties grown are resistant to both RLN species.
Professor John Thompson, Crop Nematology, Centre for Crop Health
University of Southern Queensland
07 4639 8806
GRDC Project Code DAQ