Crown rot resistance closer in durum wheat by Bernie Reppel
THE 'HOLY Grail' quest for crown rot resistance in durum (pasta) wheats is moving ahead, with the identification of promising resistance in durum cultivars from Morocco and in lines of 'goat grass', a wild relative of wheat, passed to Australia by French researchers.
The lines of 'goat grass' (Triticum turgidum ssp. carthlicum) possess both seedling and adult plant resistance to crown rot, while the Moroccan lines possess adult plant resistance.
When scientists and plant breeders "pyramid" these new resistances with other sources of partial crown rot resistance from durum and bread wheats, they will strike a major blow at a disease identified by the 2001 Durum Industry Conference in Adelaide as "one of the major impediments to the expansion and viability of the durum industry in Australia".
Crown rot is a major, soil-borne disease problem for durum wheat growers around Australia, slashing yields - by up to 50 per cent, more frequently by 20-30 per cent - and quality, primarily through the production of small grain.
Australia's current durum cultivars, Kamilaroi, Yallaroi, Wollaroi and Tamaroi as well as the recently released EGA Bellaroi are all highly susceptible to crown rot.
The breakthrough was made by Queensland Department of Primary Industries principal plant pathologist Graham Wildermuth, working on a GRDC supported project to breed durum wheats with crown rot resistance.
Dr Wildermuth's research also holds some prospect of resistance to the closely associated disease Fusarium head blight, which has had similar devastating effects on wheat crops in northern NSW.
Head blight is caused by the fungus Fusarium gramininearum and crown rot by Fusarium pseudograminearum. Dr Wildermuth says there is some evidence from his own research with bread wheat varieties, and from similar investigations overseas, that resistance to crown rot in some lines is linked with resistance to Fusarium head blight.
Lines incorporating some of the identified resistances are being tested in tbe field this winter cropping season, under the Enterprise Grains Australia durum wheat breeding program.
"Besides more reliable durum production, crown rot-resistant varieties will give producers more confidence in retaining stubble in areas where the disease is a problem," Dr Wildermuth said.
"Crown rot in a durum crop leaves high levels of inoculum to carry-over into following seasons, prompting growers to burn, rather than retain, beneficial stubble. Resistant varieties will reduce levels of disease inoculum likely to be carried over to following crops in durum stubble.
"It's also interesting that we noted a number of the Triticum carthlicum lines obtained from France produced crowns at a shallow depth in, or on, the soil surface.
"Earlier research in Australia has shown that resistance to crown rot in some bread wheat varieties and lines was related to shallow crown formation and that may also be occurring in these durum lines."