Recent Advances in \u3cem\u3eStylosanthes\u3c/em\u3e Research in Tropical America

The potential of neotropical savannas is very large for pasture-based livestock systems. There are 250 million ha of well-drained lowland savannas in the American tropics. Over 200 million ha are situated in the Cerrados region of Brazil. The Cerrados support 42% of the national herd. Although these ranges support large populations of livestock, productivity is generally low. Poor nutritive value of native pastures and monospecific swards of Brachiaria spp. is the principal cause of this low productivity, especially in the dry season when these grasslands often provide no more than 60% of the animal\u27s maintenance requirements. The best option to increase pasture/livestock productivity is the use of improved pastures, particularly those based on adapted tropical legume-grass associations. Research in tropical America was concentrated on the evaluation and selection of Stylosanthes species adapted to low fertility acid-soils and resistant to anthracnose (Colletotrichum gloeosporioides). Anthracnose is considered the major limitation to the commercial use of Stylosanthes on a world-wide basis

A Novel Technique to Produce Polygenic Resistance to Anthracnose in \u3ci\u3eStylosanthes capitata\u3c/i\u3e

An improved cultivar, based on 17 genotypes of S. capitata and six of S.macrocephala, was developed at the Embrapa Beef Cattle Research Center, Campo Grande, Brazil. The aim was to create durable, race non-specific resistance to anthracnose controlled by polygenic factors. A mass hybridisation technique was employed to produce a high degree of genetic diversity and sizeable quantities of seed of hybrid-derived progenies of Brazilian and Venezuelan genotypes of S. capitata. Outcrossing resulted in a significant improvement in the forage production of progeny of Venezuelan accessions. The multicross was evaluated in multilocational trials, each representing a large tract of country in the Cerrados ecosystem along a north-south transect from lat.60 S to 200 S. The genetic shift that occurred in S. capitata was a key element in the formation of the new cultivar. It is a complex mixture of two species, and a recombination of much desired forage traits of Brazilian x Venezuelan genotypes, high forage and seed yields coupled with anthracnose resistance. The new cultivar with its diverse genetic make-up has a wide application in the acid-soil savannas of tropical America. It was released by Embrapa for the Cerrados in 2000

New \u3ci\u3eStylosanthes guianensis\u3c/i\u3e for Tropical Grasslands

Hybrid stylos (Stylosanthes guianensis var. vulgaris x var. pauciflora) with durable, quantitative resistance to anthracnose, mid-season harvest maturity date (early-July), high DM and seed yields have been selected at the Embrapa Beef Cattle Research Center, Campo Grande, Brazil. The hybrids displayed improved forage traits in Brazil, the native habitat and major center of diversity of the species and its pathogen, as well as in vastly different ecosystems. Dry forage yields and anthracnose resistance of superior selections and their composites were equal, in some instances, significantly better, than those of cv. Mineirão in multilocational trials situated in the Cerrados from lat. 6° S to lat. 20° S. Selected hybrids performed well in comparison with the highly successful CIAT184 (cv.Reyan II) on Hainan Island, China. Composites have also shown good promise in seed multiplication plots in Queensland, Australia. A positive attribute of composite hybrids is their great genetic diversity in contrast to pure-line cultivars with a relatively narrow genetic base. These truly tropical forms of stylo are best adapted to regions with \u3e1500mm average annual rainfall

Pasture species evaluation

72 páginasThe paper refers to an evaluation of grass and legume species at the Cerrados Agricultural Research Center (CPAC). The evaluation of forage species, a CIAT/EMBRAPA/IICA Collaborative Project, with the primary objective of identifying grasses and legumes adapted to Cerrados conditions and grazing utilization has been in progress at the Cerrados Agricultural Research Center (CPAC), Planaltina since 1978

Estilosantes Campo Grande in Brazil: A Tropical Forage Legume Success Story

Estilosantes Campo Grande (ECG) is a mixture (80/20 by weight) of Stylosanthes capitata and S. macrocephala, derived through genetic combination of selected accessions by open crossing over 6 generations (Grof et al., 2001). The cultivar is the result of \u3e10 years of research on a collection of \u3e1000 ecotypes of Stylosanthes species collected and maintained by Embrapa. The main use of ECG in Brazil is to improve grass-dominant pastures. It has good persistence with Brachiaria spp., Panicum maximum (Tanzania-1 and Mombaça) and Andropogon gayanus. It has excellent adaptation to low fertility sandy soils and is persistent under grazing. In regional trials, ECG was the best performer in S Brazilian Cerrados, where the dry season is less severe. Although it does not retain foliage after the rainy season in areas with long and intense dry season, it still contributes to nitrogen fixation and animal nutrition during the rainy season. It is a prolific seed producer and seedling recruitment is its main mechanism of persistence. More than 500t of ECG seed has been produced since its commercial release and the estimated area planted to this cultivar has increased from \u3c500ha in 2000 to nearly 150Kha by 2004, mainly in the Brazilian Savannas

Small-sward testing of Stylosanthes in Northern Australia: Preliminary considerations

An experiment is described in which 27 accessions of Stylosanthes, comprising some seven species, were grown for 3 years in small swards at eight different sites covering a wide range of environments. The accessions used were selected on the basis of previous studies, so as to represent a wide range of species and species forms. Numerical data was used to delineate those species, or species forms, likely to be of agronomic value in the various areas. The implications of the methods used and the results obtained are discussed in relation to plant introduction and plant evaluation techniques