Ground Cover Supplement : GC Supplement - Biosecurity
GROUND COVER BIOSECURITY 16 DIAGNOSTICS & PRE-BREEDING Overseas and over here Taking a global and local approach to tracking and responding to disease threats is essential By Robert Park and Colin Wellings BIOSECURITY PEST AND disease threats can come not only from exotic incursions, but also from the local development of new pathotypes from pathogens already in Australia, resulting in the breakdown of plant resistance. For the rust diseases of cereals, history has time and again provided examples of both threats. At the University of Sydney's Plant Breeding Institute (PBI), methods to rapidly detect exotic and mutated pathotypes continue to be developed and improved. Stem rust The recent outbreak of stem rust in wheat in South Australia highlighted a possible mutation in the stem rust pathogen, enabling it to overcome the resistance gene Sr26. A two-pronged approach was used to determine if a mutation had in fact occurred. Tests at the University of Adelaide by Dr Ian Dundas and at CSIRO Plant Industry by Dr Rohit Mago established within days that the suspect crop did not carry the resistance gene Sr26, and hence was unlikely to be the cultivar Kite, as had been reported. Greenhouse tests of the rust at the University of Sydney by Professor Robert Park established within two weeks that the isolate present was an existing pathotype and that no mutation had occurred. Fortunately, resistance gene Sr26 (present in cultivars such as Currawong, Petrel, Snipe, Sunlin and WylahA) remains effective in Australia. In terms of external threats, an incursion of the exotic stem rust pathogen Ug99 could render 27 of Australia's 89 listed wheat varieties more susceptible to stem rust. Of these, six are anticipated to become fully susceptible. Pathologists from across the globe, including Australia, are tracking the progress and evolution of the Ug99 stem rust lineage. Named after its initial detection in Uganda in 1999, this pathotype concerns the international wheat- breeding community because it overcomes many of the resistance genes bred into modern wheat cultivars. However, eight independent genes that are effective against Ug99, including Sr26, are either available or already in use. Forty-four commercial varieties have one or more genes for resistance to Ug99. Seven pathotypes referred to collectively as the Ug99 lineage have been identified; these vary in their ability to overcome wheat stem rust resistance genes. One or more of these pathotypes have been identified in east Africa, New mutations of wheat-attacking stripe rust pathotypes that are already in Australia are a continuing internal biosecurity threat.
GC Supplement - Capacity building
GC Supplement - Grain storage