Synthetic wheat? Back to basics for yield and disease resistance by Guy Cotsell

Remaking the modern wheat gene line up.

AN international project is going back to the ancestors of modern wheat to recruit genes that have the potential to improve drought tolerance and resistance to heat stress and disease in Australian wheat.

Synthetic wheat, developed by scientists in Australia, in the US and importantly at the International Maize and Wheat Improvement Centre in Mexico (CIMMYT), is the vehicle to introduce these ancient genes into our modem varieties.

Synthetic is not always a good word in our present-day supermarket culture, sometimes implying something secondbest, or not quite the real thing. But the synthetic wheat lines being developed under this joint project have impeccable pedigrees - they are crosses which might have happened naturally thousands of years ago, but didn't.

Wheat originated with three different wild plant species, one of which resembled our modern durum. In the wild these species crossed with goat grass, a close relative of modern wheat, and in doing so acquired some useful genes.

But this crossing probably occurred only two or three times during the development of our present-day wheats, which as a result possess some - but not many - of the 'good' genes from goat grass and durum wheat. So researchers had another look to see what else goat grass might have to offer, and found a wide range of 'good' genes such as resi stance to di sease of nematodes, crown rot and yellow spot.

To get these genes into our modern wheats, scientists are now 'remaking' wheats by going back to the original goat grass and crossing it with modem durum to make some of the crosses that didn 't happen in nature. The material is rich - between 200 and 300 different types of goat grass have been collected in the Middle East and Asia. Many are carrying genes that could benefit present-day crops.

Both CIMMYT and Kansas State University set up major programs to make these crosses and then to evaluate crosses between the synthetics and bread wheat. CIMMYT has developed about 800 synthetic lines. They form a 'genetic bridge' to cross with modern wheat.

Drought tolerance and resistance to heat stress

As work progressed, researchers realised some of the new crosses gave high yields and could tolerate drought and heat stress during grain-filling. A GRDC-supported project involving the CSIRO, the Victorian Institute for Dryland Agriculture at Horsham and the Queensland Department of Primary Industries at Toowoomba is now looking at whether these characteristics can be introduced into Australian varieties.

The project is working with CIMMYT to develop crosses from Australian durums, then to cross these synthetics back to Australian wheat. Horsham researchers are working on resistance to cereal cyst nematode and at Toowoomba the focus is resistance to yellow spot, crown rot and root lesion nematode. Both are looking for higher yield.

Trials in Mexico are reported to have successfully grown drought-tolerant wheat on as little as 150 mm of water for the entire growing season.

In a recent report on GRDC investments in CIMMYT, GRDC consultant Paul Brennan paid tribute to the energy and magnitude of the CTMMYT effort in this project. Dr Brennan pointed out that Australian scientists had been using CIMMYT germplasm for 30 years and this had provided an estimated $4 billion benefit to Australian wheatgrowers.

Program 1.6.4 Contact: Dr Paul Brennan 02 6687 5288

Region North