In this section:
Medics
Medics are the backbone of the annual pastures research.
Annual medics (Medicago spp.) in southern Australia's semi-arid agricultural zones provide feed for livestock as well as benefit the following cereal crop by improving soil fertility through nitrogen fixation and also by providing disease break for various cereal root pathogens. These self-regenerating pasture species have relatively high levels of hardseededness, which enables them to persist through cropping phases and regenerate in subsequent years as pasture. Medicago truncatula Gaertn. (barrel medic), M. littoralis Rohde ex Lois. (strand medic), M. tornata (L.) Mill. (disc medic) and M. polymorpha L. (burr medic) constitute the predominant species grown.
Breeding Program
Currently, the SARDI Annual Pasture Legume Improvement program in collaboration with the National Annual Pasture Legume Improvement Program (NAPLIP), funded by the Grains Resarch and Development Corporation (GRDC) and Australian Wool Innovation (AWI) and through its own resources is pursuing a number of objectives.
These include:
- high dry matter production
- resistance to pests and diseases
- tolerance to SU (Sulfonyl urea) herbicide residues
- time to maturity
- improved nitrogen fixation
- different levels of hardseededness and pod spininess.
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Comparison of an aphid susceptible M. truncatula cv. Jemalong compared to an aphid resistant M. truncatula cv. Jester (resistant to both blue-green aphid and spotted alfalfa aphid). |
Comparison of a SU herbicide sensitive M.littoralis cv. Herald compared to a SU herbicide residue tolerant M. littoralis cv. Angel in a field demonstration trial. |
Agronomy and Evaluation
Annual medics are evaluated in the cereal/ livestock zone of South Australia at sites typically with low/ medium rainfall (250–400mm), neutral to alkaline soils. These include sites on the Upper Eyre Peninsula, Murray Mallee, Mid North and Upper South East.
The primary objective is to evaluate and select new cultivars with improved performance and/ or enhanced features for the cereal/ livestock areas. Feedback is also provided to the breeder with respect to the identification and performance of germplasm potentially suitable as parents in future breeding projects.
Factors taken into consideration include:
- early vigour
- winter and spring dry matter production
- herbicide tolerance
- seed yield
- hardseededness
- regeneration
- persistence
- insect and disease tolerance.
Larger scale agronomic work is undertaken with commercially available varieties including investigating the performance of medics in pasture mixtures with different species, the use of different herbicide options and their effect on pasture botanical composition and productivity, and large scale demonstrations of the adaptation of a range of cultivars over different soil types.
Medic Cultivars
A major project has resulted in the development and commercialisation of Angel (.PDF), a new strand medic with excellent tolerance to sulfonylurea residues.
In 2005 the South East Pastures group initiated a trial to investiage soft-seeded burr medics. This was in response to the relatively poor regeneration of burr medics in the year after sowing. Burr medics may play a valuable role in the saline environments of the Upper South East and possibly on the heavy 'black flats' west of Naracoorte. Burr medics include Scimitar and Cavalier (.PDF).
Other annual medic cultivars include Caliph (.PDF), Cavalier (.PDF), Herald (.PDF), Jester (.PDF) and Mogul (.PDF).