Cereal rust corner with Dr Colin Wellings* and Dr Robert Park, University of Sydney, Plant Breeding Institute Cobbitty (Dr Wellings is on secondment from NSW Agriculture): Stripe rust proofing barley

CEREAL rust diseases are caused by pathogenic fungi that are highly specific in the host plants they attack. For example, the stem rust pathogen has several specialised forms with distinct host ranges, known as forma speciales (f. sp.) or 'special forms'.

Australia has so far been spared a form of stripe rust specialised on barley, and known as P. striiformis f. sp. hordei. This pathogen caused significant damage in South America when first introduced from Europe in 1975 and in 1991 spread to North America. Australian barleys tested at CIMMYT, Mexico, have proved to be generally susceptible to barley stripe rust. A summary of data from a CIMMYT nursery is presented in the accompanying table. It is clear that our current cultivars will be vulnerable to any introduction of this rust.

A research program supported by growers and the Federal Government through the GRDC has recently expanded to allow testing of barley breeding popUlations in Mexico to select for resistance to the barley form of stripe rust. In this way, it is planned that commercial barleys resistant to barley stripe rust will be available in advance of a potentially damaging exotic pathogen introduction.

Response of Australian barley cultivars exposed to P. striiformis hordei Race 24 in field plots at CIMMYT, Mexico (1999)

DISEASE RESPONSE

Resistant: less than 10 per cent leaf area affected; moderately resistant: 20- 40 per cent; moderately susceptible: 50-80 per cent; susceptible: over 90 per cent affected.

Resistant:
Malebo, Tallon, Tilga, Yerong

Moderately resistant:
Brindabella, Galaxy, Grimmett

Moderately susceptible:
Barque, Cask, Gilbert, Mundah, O'Connor, Stirling, Windich

Susceptible:
Arapiles, Chebec, Corvette, Fitzgerald, Franklin, Galleon, Gairdner, Kaputar, Molloy, Moondyne, Namoi, Onslow, Schooner, Skiff, Sloop, Tantangara, Weeah, Wyalong, Yagan