Formacao da base genetica e manejo dos recursos geneticos de mandioca: O caso do Brasil

The concept of genetic erosion is discussed, with particular reference to cassava in Brazil. National germplasm collections are listed with the corresponding no. of accessions; information is also provided on the plant breeding activities carried out. The potential of interspecific crossbreeding in cassava with wild Manihot species is discussed. In Brazil, wild Manihot species, particularly in the form of seed, are collected by the Centro Nacional de Recursos Geneticos (CENARGEN); both a small seed stock (15 species) and a small live collection (20 species) are maintained. The collection of woody wild species is considered prioritary. The interactions of CENARGEN with active germplasm collections in the country are indicated regarding collection, internal exchange, and germplasm introduction. A tentative organizational chart of a cassava germplasm collection is included. General indications are also provided on the handling of genetic resources. (CIAT)Se discute el concepto de la erosion genetica, con particular referencia a la yuca en Brasil. Se enumeran las colecciones nacionales de germoplasma con el no. correspondiente de accesiones; tambien se proporciona informacion sobre las actividades de fitomejoramiento desarrolladas. Se discute el potencial del cruzamiento interespecifico en yuca con especies silvestres de Manihot. En Brasil, el Centro Nacional de Recursos Geneticos (CENARGEN) recolecta las especies silvestes de Manihot, particularmente en forma de semilla; tambien mantiene una limitada reserva de semilla (15 especies) y una pequena coleccion viva (20 especies). La recoleccion de especies silvestres lenosas se considera prioritaria. Se indican las interacciones de CENARGEN con las colecciones de germoplasma activa en el pais en cuanto a recoleccion, intercambio interno e introduccion de germoplasma. Se incluye un organigrama tentativo de una coleccion de germoplasma de yuca. Tambien se proporcionan indicaciones generales sobre el manejo de recursos geneticos. (CIAT

Cassava germplasm strategies for Africa

The types of germplasm needed for the different agroecological zones where cassava is grown are outlined briefly in terms of what the main supplier (South America) has to offer. Africa's Atlantic coastal belt, its tropical rain forests, its extensive savannas, and the arid zones are examined in relation to similar zones in South America, with particular emphasis on Brazil, which alone can meet most African needs thanks to the diversity of its edaphoclimatic environments. The topic of genetic erosion is also addressed; there is no tangible evidence, however, that cassava is undergoing serious genetic erosion in its centers of origin (American neotropics). Major cassava germplasm collections are listed for the Americas, Africa, and Asia. Genetic resources of wild Manihot species are also reviewed. Future strategies should consider more temperate latitudes farther south, salinity, atmospheric humidity, and reproductive biology. High priority should be given to collecting germplasm for transfer to African regions, as follows: coastal cv., riverine cv., cv. with yellow flesh, drought-tolerant cv., and wild populations of cassava in the neotropics. (CIAT)