WHEAT varieties that feature improved root-lesion nematode (RLN) resistance are in the pipeline thanks to a GRDC-funded project that has identified resistance genes in wheat cultivars from Australia and CIMMYT, the world's wheat-breeding hub in Mexico, and landraces (traditional, local varieties) from Morocco, Iran and Iraq.
Under the University of Southern Queensland's Centre for Crop Health (CCH) professor of crop nematology John Thompson and project leader and CCH crop nematologist Jason Sheedy, the research into genetic options for nematode control started in 2011.
Five resistant and tolerant cultivars that out-yield current commercial varieties have already been delivered to the major breeding companies in Australia.
The recipients include AGT, LongReach, InterGrain and Dow. "In the project we've brought in genes from a number of different sources," Professor Thompson said.
"They include landrace varieties selected by farmers over many generations to suit local conditions, and synthetic hexaploids - lines made by recreating the natural hybridisation process that produced bread wheat from durum and goat grass in the Middle East 10,000 years ago, into our northern-region wheat germplasm."
Initial evaluations of the newly developed resistant and tolerant cultivars have shown yield increases of up to 8 per cent over the popular tolerant variety EGA Gregory.
The research has also indicated significant reductions in nematode populations left in the soil to attack a following crop.
"We have been charged with increasing the genetic diversity of RLN resistance and incorporating that diversity into varieties suitable to each of GRDC's three grain regions, and the companies are now making further crosses to release commercial nematode-resistant varieties."
COMMENT THE NEED
Professor Thompson says wheat producers are now able to reap the rewards of the partnership between GRDC-funded pre-breeding and commercial breeding with wheat transitioning from a mostly intolerant and susceptible crop to having the combination of tolerance and resistance available in varieties like Gauntlet, Suntop and Sunmate.
This was particularly important, given that about 85 per cent of paddocks in southern Queensland and northern NSW and 28pc in central Queensland have the RLN species Pratylenchus thornei or Pratyelnchus neglectus or both present.
RLN THE COSTS
- Long-term trials at Jondaryan have found RLNs cause wheat yield loss in nine years out of 10, and cost intolerant varieties up to 50 per cent of their yield potential, Professor Thompson says.
- RLNs are all female, and lay their eggs in roots, which hatch and cause an exponential build-up of numbers which can hit the plant hard at the tillering stage, causing it to produce a lower number of tillers and heads, and appear nutrient and water stressed.
- A damaging population is considered to be 2000 per kilogram of soil, and P. thornei is estimated to be at this level in 30pc of affected paddocks in southern Queensland and northern NSW, compared with only 5pc for P. neglectus.