Crown rot continues to grow in status as a serious crop disease, largely because of the increasing adoption of reduced tillage farming, which leaves inoculum of the fungus on the soil surface and therefore in close contact with the susceptible stems of plants. Most wheat varieties are susceptible, although a few, such as some derived from Cook and Sunco, are less susceptible. A few varieties, such as Batavia, are significantly more susceptible than others and it is these varieties where most of the serious crop damage occurs.
These highly susceptible varieties include all durum varieties, and it is the durum industry in both the northern and southern regions that most need the development of resistant varieties. While there has been some progress for bread wheat varieties, durum remains a challenge.
Improved resistance to crown rot in bread wheat has been identified. Molecular markers have been identified by groups working at SARDI and at the University of Southern Queensland and Leslie Research Centre. These markers allow wheat breeding programs to fast-track the development of new breadwheat breeding lines with greater resistance to the disease. Wheat crop sown back onto previous cereal row.
Trying to repeat this in durum is much more difficult. Until now, no one has been able to identify any durum varieties or breeding lines with better resistance. For this reason the search for useful resistance has moved in recent years to searching among wild species closely related to durum wheat. Included among these are some lines known as Triticum dicoccum, which have been held in the Australian Winter Cereals Collection in Tamworth.
Dr Hugh Wallwork at SARDI has screened these over several years and identified three that have repeatedly shown partial resistance to crown rot. While these tests have been under way, he has also been using them as parents to see whether the resistance could be successfully transferred into an adapted variety. Now, at what is termed the BC1F4 generation and after some initial selection, the results of this work will be fully tested in the field and in replicated pot tests.
"By the end of 2005 we should know whether these wild parents can be used to help develop durums that have adequate resistance to avoid most problems with crown rot," Dr Wallwork says. "If the answer is positive then we are already well on the way to developing better varieties."
GRDC Research Code DAS000222
For more information: Dr Hugh Wallwork, 08 8303 9382, email@example.com Package offer on Cereal Root and Crown Diseases, ground cover direct, page 31