Stylosanthes is a fast-growing, tropical leguminous plant with various uses. In India it is the most important tropical legume for semi-arid and arid regions, mainly used in livestock production and in restoring soil fertility. In China it is mainly used as a green manure for soil enhancements, and in feed meal productions. Its nitrogen-fixing properties also help replenish soil nutrients in ley farming and intercropping systems. It also helps restore marginal lands with infertile acid soils and is important in revegetation programs.
Stylosanthes is also important in Central and South America, Africa and other Asian countries. The beef industry in northern Australia increasingly relies on Stylosanthes as a pasture plant for cattle. However, the major constraint to its use, wherever it is grown, is the fungus diseases anthracnose. The fungus is diverse and quick to adapt, and with growing international travel and trade the risk of even more damaging fungal strains entering Australia, India or China is increasing.
In this project Australia contributed its recognised experience in tropical pasture technology - its Stylosanthes expertise in particular - to help combat the anthracnose disease problem.
The aim of the project was to select strains of Stylosanthes resistant to anthracnose, with the ultimate intention of providing high-yielding, disease-resistant varieties of Stylosanthes that perform better on the farms of India, China and northern Australia.
Scientists sought Stylosanthes germplasm with high resistance to anthracnose, as well as good yields of herbage and seed. Research had already resulted in a number of promising lines, but access to new sources of germplasm was also sought. Selection and recombination were then carried out in the search for resistant but high-yielding cultivars suited to different soil, climatic and agronomic requirements.
Using molecular markers, researchers also developed a genetic map for Stylosanthes to improve understanding of the genetic determinants of anthracnose resistance.
The third strand of the work focused on the epidemiology of anthracnose disease. New strains of the fungal pathogen can arise without warning, and a high level of genetic variation in the fungus had been detected in many populations already studied. The scientists studied the fungal populations in all participating countries to produce a catalogue of the range and extent of variation. Molecular markers were used to track gene flow between populations in different countries.
The project was initiated in 1998-2001 with a primary focus on upstream research aimed at collecting baseline data and developing improved germplasm and varieties with anthracnose resistance and high yield. The focus of the extension (2001-2003) shifted to market analysis and commercial development. Although extension and technology transfer were not major components, there was considerable promotion and uptake of project accessions.
The project made excellent progress against all objectives. There was extensive screening of lines from all partners and many showed excellent resistance. The project contributed to the release of two cultivars of Stylosanthes seabrana for Maharashtra in India, two S. guianensis cultivars named Reyan7 and Reyan10 in China, and one S. capitata-S. macrocephala multiline cultivar 'Estilosantes Campo Grande' in Brazil. Quantitative traits loci (QTLs) for resistance were mapped and several are available as markers. Studies of anthracnose epidemiology and risk mapping have given, for the first time, a clear understanding of the genetic structure and virulence of the C. gloeosporioides population in all participating countries.
Good information has been collected on the current state and future potential for commercial leaf meal and seed production in India. Leaf meal production is being largely undertaken by smallholder farmers who interact with large poultry producers through farmer cooperatives. This is being supported by a vigorous stylo seed production sector of smallholder farmers growing high-yielding anthracnose-resistant varieties developed in this project. The gradual replacement of existing cultivars with high-yielding and resistant varieties for the cropping, horticulture and wasteland development sectors will mainly be demand-driven, as benefits of growing the new varieties become apparent through ongoing demonstrations by government and NGOs.
Early indications of farmer-level impacts are available from the 'Surashettykopa' cluster of villages near Dharwad in India. BAIF, a local NGO, started participatory work in 1998 on stylo and other forage seed production and selected farmers were given hands-on training at research farms, where they received seeds and other inputs. The initial figure of eight farmers producing S. hamata and S. scabra seeds in the first year has increased to >115 farmers in 5 years. According to BAIF, the benefits to smallholder farmers (<2 ha) from growing stylo as a component of the whole-farm improvement program has been exceptional. Other indications of impact come from the gradual replacement in commercial seed production of the susceptible cultivar Fitzroy by the highly productive and resistant S. seabrana accessions promoted by the project. Many other stylo cultivars will be released as a result of project research in partner countries.
The project established a stylo web site: www.csiro.au/stylointernational. Project experiences and findings are also described in an ACIAR publication entitled 'High-yielding Anthracnose-resistant Stylosanthes for Agricultural Systems'.
The broad testing of extensive Stylosanthes germplasm in 20 sites across the world, the release of several Brazilian and Chinese cultivars, the knowledge gained on the nature of pathogen populations in India, Brazil and Australia, and the novel information on the anthracnose disease threats to Australia from China and India, are all examples of sound scientific achievements and outputs. It has expanded the scientific base considerably for continued and targeted improvement in anthracnose resistance in Stylosanthes in China, India and Brazil, and this will greatly assist the livestock industries of these countries.
Links:
[1] http://www.aciar.gov.au/country/China
[2] http://www.aciar.gov.au/country/India
[3] http://www.csiro.au/stylointernational
[4] http://www.csiro.au/people/ps1lg.html
[5] http://www.aciar.gov.au/programarea/Crop Improvement and Management