Molecular characterization of Cassava (Manihot esculenta Crantz) with yellow-orange roots for beta-carotene improvement

Abstract

Casssava (Manihot esculenta Crantz) is one of the main food and income sources of about 500 million people in the tropics. The crop is mainly cultivated by small farmers in tropical Africa, Asia and Latin America. Embrapa Mandioca e Fruticultura Tropical, based in Cruz das Almas, Bahia, maintains one of the largest cassava genebanks of Latin America. Among the accessions it contains, those with yellow-orange root color are particularly interesting. The objective of this study was to characterize 30 cassava accessions with yellow-orange root color by RAPD markers. The genetic distances of the 47 analyzed primers varied from 9.0 to 31.7 %, demonstrating the existing genetic variability to be exploited for the development of cassava varieties with higher beta-carotene contents. Molecular characterization of Cassava (Manihot esculenta Crantz) with yellow-orange roots for beta-carotene improvement Claudia Fortes Ferreira1*, Elaine Alves2, Katia Nogueira Pestana3, Davi Theodoro Junghans1, Adilson Kenji Kobayashi4, Vania de Jesus Santos3, Raimundo Pereira Silva1, Paulo Henrique Silva3, Ediclan Soares3, and Wania Fukuda1 1 Embrapa Mandioca e Fruticultura Tropical, s/n, C.P. 007, 44.380-000, Cruz das Almas, BA, Brasil, *E-mail: claudiaf@cnpmf.embrapa.br 2 Universidade Federal da Bahia (UFB), Rua Basilio da Gama, s/n, Canela, 40.110-907, Salvador, BA, Brasil 3 Universidade Federal do Reconcavo Baiano (UFRB), Campus Universitario da UFRB, 44.380-000, Cruz das Almas, BA, Brasil 4 Embrapa Meio-Norte, Av. Duque de Caxias, 5650, Buenos Aires, 64.006-220, Teresina, PI, Brasil INTRODUCTION Manihot esculenta Crantz is a species native to tropical America (Olsen and Schaal 2001), initially cultivated by native Latin Americans and later introduced into the African and Asian continents. The worldwide cassava production, on an area of 17.870.626 hectares is approximately 195.574.112 tons (FAO 2004). It is considered one of the most important sources of calories and is an inexpensive staple food in Latin America (Montero 2003), mainly in the northeastern region of Brazil (Mendes et al. 2006). The genetic diversity of this species is wide (Nassar 2006), concentrated mainly in Latin America and the Caribbean. Approximately 8500 cassava accessions are maintained worldwide in different collections, of which 7500 in South America (Costa and Morales 1994). Received 24 January 2007 Accepted 07 November 2007 In Brazil, 4132 accessions have been collected and are maintained in genebanks across the country (Fukuda 2000). Carotenes (-carotene, b-carotene, lycopene) represent the most multifaceted group of pigments in nature, with colors varying from yellow to red, found in photosynthetic and non-photosynthetic tissues, such as roots, seeds and fruits. Once ingested, b-carotene is transformed, in the liver, into Vitamin A. Vitamin A is a micro-nutrient with functions related to vision, cell differentiation, growth development, reproduction and the immune system. Vitamin A deficiency (VAD) can cause severe diseases, e.g., ocular syndrome, xerophthalmia, and advance to irreversible blindness (Underwood et al. 1999). Although the lack of vitamin A can be prevented, xerophthalmia is still a public health problem in many developing countries (Welch and Graham 2002).