Ground Cover Supplement : GC Supplement - Pastures
LUCERNE GROUND COVER PASTURES 14 IMPROVING PERSISTENCE AND productivity in lucerne varieties being developed for grazing is the key focus of the breeding program targeting the southern Australian cropping zone. In breeding lucerne specifi- cally for this region, improved tolerance to grazing was identified as the highest priority, in addition to maintain- ing levels of insect and disease resistance and improving tolerance to soil acidity. A continuous grazing trial at Roseworthy, SA, evalu- ated 120 varieties of lucerne from 1999 to 2003. Plants surviving two years of continuous grazing were dug up and replanted in the South Australian Research and Development Institute (SARDI) breeding nursery to form new lines for further evaluation. In 2003, two new continuous grazing trials were sown. An acidic light sandy soil at Katanning, WA, was selected to see if grazing tolerance would con- tinue on a soil more conducive to physical disturbance from the trampling of sheep. The second trial was sown at Turretfield, SA, in a similar environment to Roseworthy. The evaluation of some 70 varieties and breeding lines has shown very encouraging results. All 10 of the new lines developed at Roseworthy were found to main- tain substantially higher plant densities than commercial varieties and other breeders’ lines in both of the new trials following nearly two years of continuous grazing by sheep. In comparison, existing varieties have col- lapsed and become useless due to their very low plant frequency and low ability to maintain production under grazing (Figure 1). The exciting parallel results between Turretfield and Katanning are further aided by the fact that these lines outperformed other breeders’ lines and cultivars in farmer-managed field trials at Cunderdin, WA, and Sherlock, SA. To ensure the new variety will be grazing-tolerant and maintain other desirable traits in lucerne, about 300 Grazing-tolerant lucerne: persistence and productivity PROJECT: BREEDING LUCERNE FOR SOUTHERN AUSTRALIAN CROPPING DISTRICTS. ALAN HUMPHRIES southern Queensland by the Queensland Department of Primary Industries and Fisheries. PegasisA has been developed for short-term lucerne rotations and sustain- able cropping systems. It has proved in field trials to be more persistent than other highly winter-active varieties, which will create opportunities to retain pasture phases for longer where desired. PegasisA is: n high-yielding and highly winter active; n rated as highly resistant to spotted alfalfa aphid, resistant to Phytophthora root rot and moderately resistant to Colletotrichum crown rot; and n very leafy and densely branched with a large spread- ing crown. As a highly productive and well-adapted lucerne variety, PegasisA has the following features: n increased grain yield and grain protein level in the cropping phase, improved environmental sustainability and increased profitability; n competitive stands in crop rotations will diminish weed incidence, reduce herbicide use and correspondingly delay the development of herbicide- resistant weed species; n the deep root system will use excess water and nutrients to offset the waterlogging, salinisation and acidification of soils; n selected for improved yield and persistence will increase forage production and animal productivity to increase farm income; and n grain yield depression in subsequent crops due to disease will be reduced, providing an effective disease-break between grain crops. PegasisA will be the first lucerne variety to be released through the Australian Lucerne Alliance (ALA), a partnership between the NSW DPI, the GRDC and Seedmark. This alliance combines ‘state-of-the-science’ lucerne breeding processes under a commercial man- agement consortium, as well as ‘state-of-the-industry’ marketing processes to ensure that new and improved lucerne varieties are successfully used by growers. PegasisA will complement previous releases from the NSW DPI lucerne breeding program that have included Nova – the first Australian-bred variety resistant to spot- ted alfalfa aphid; Aurora – a superior general-purpose variety bred with multiple pest resistance; AquariusA – the first variety in Australia to be bred with high resis- tance to Phytophthora root rot; GenesisA – general pur- pose winter-active variety with high forage yields and persistence; and VenusA – semi winter-dormant variety developed for persistence and yield under dryland con- ditions for long-term pasture rotations. Australian-bred lucerne varieties provide a great ‘home-grown’ plant resource for Australian farmers. Tim O’Brien is assistant research agronomist, Lucerne Breeding Program, NSW DPI. GRDC Research Code DAN484 More information: Tim O'Brien, 02 6763 1205, firstname.lastname@example.org Continuous sheep grazing trial on lucerne at Turretfield, South Australia.
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