Ground Cover Supplement : GC Supplement - Cereal foliar fungal diseases
14 Non-rust fungal diseases YELLOW SPOT RESISTANCE ON THE WAY nationally, yellow spot is rated as the second most damaging wheat disease behind stripe rust, costing growers up to $30 per hectare in lost production and control costs in hard-hit areas By Janet Paterson WHEAT VARIETIES WITH resistance to yellow spot (also known as yellow leaf spot or tan spot) could be available within the decade following the discovery of eight genes conferring good resistance to the costly disease. Leader of the national GRDC project Dr Manisha Shankar, from the Department of Agriculture and Food, Western Australia (DAFWA), says more resistance genes are on the horizon and that 16 lines with three 'stacked' genes have already been delivered to breeding companies across Australia. "The breeding lines have been tested for yellow spot resistance under controlled conditions at both the seedling and adult plant stages and all show good levels of resistance," Dr Shankar says. The research team is now focused on stacking five to six of the genes into both short and long-season wheat breeding lines. "These stacked lines should be directly useful as parents in wheat breeding programs." Each of the genes has a corresponding marker developed through the Australian Wheat and Barley Molecular Marker Program, based at the University of Adelaide, enabling breeders to keep track of multiple genes during variety development. Dr Shankar and colleagues from across Australia have screened nine mapping populations to find the eight genes that confer yellow spot resistance. In addition, they have sifted through nearly 900 international wheat lines to find new sources of resistance to yellow spot. Many of the lines were imported from the International Centre for Agricultural Research in the Dry Areas (ICARDA) and the International Maize and Wheat Improvement Center (CIMMYT), through the CIMMYT-Australia-ICARDA Germplasm Evaluation (CAIGE) project. Before the national pre-breeding project started in 2010, relatively few yellow-spot-resistance genes had been identified and mapped in Australian germplasm, with only one gene in general use in wheat breeding programs. Dr Shankar says this gene conferred good yellow spot resistance but did not explain the full spectrum of resistance evident in breeding trials, prompting the research team to look for other sources of yellow spot resistance. Stacked together the genes should provide a durable source of yellow spot resistance because they will take longer for the fungal pathogen to overcome. The research has also led to the development of a new screening process for yellow spot resistance in adult plants. Previously, the screening was carried out in the field and researchers had to wait until the wheat plants reached maturity to screen for resistance. "By exposing plants to continuous light in the glasshouse we can mature the plants much more quickly and, under these controlled conditions, plants have produced flag leaves within four to six weeks," Dr Shankar says. Identifying sources of adult plant resistance earlier greatly improves the efficiency of the breeding process and should speed the delivery of new varieties. The research has also improved on spore production methods, enabling researchers to produce and store large amounts of yellow spot inoculum. "This means that we can now test more genetic material, both in the field and in the glasshouse," Dr Shankar says. The 'Germplasm enhancement for yellow spot resistance in wheat' project is a collaborative project between DAFWA, the University of Adelaide, the Victorian Department of Environment and Primary Industries, the Queensland Department of Agriculture, Fisheries and Forestry and Curtin University. □ grdc research code daW00206 more information: Dr Manisha Shankar, DAFWA, 08 9368 3333, firstname.lastname@example.org PHOTO: DAFWA “the breeding lines have been tested for yellow spot resistance under controlled conditions at both the seedling and adult plant stages and all show good levels of resistance.” -- DR MANISHA SHANKAR DAFWA researcher Dr Manisha Shankar is leading a national GRDC project to increase yellow spot resistance in Australian wheat varieties.
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