Genetic diversity characterization of water yam (Dioscorea alata) with microsatellites markers

Abstract

The Dioscorea genus is the most important representative of the Dioscoreaceae family, exhibiting about 600 species distributed, over all, in the tropics, mainly in West Africa, the Caribbean and the Northeast Brazil. In Brazil, some yam species (Dioscorea spp.), like cassava (Manihot esculenta), have a significant importance in the subsistence agriculture, used basically as a carbohydrate source. Little is known about the genetic diversity and genetic structure of these species, and how it was constituted and evolved in the last years, due to the lack of molecular analysis. Thus, the main purpose of this work is to characterize the genetic diversity of landraces of Dioscorea alata originated from traditional agriculture households, and commercial varieties, with the support of microsatellite markers or simple sequence repeats (SSR). Sampling for D. alata commercial varieties cultivated in the State of São Paulo will be done in municipalities which show greater production of this crop and those will be compared with materials acquired in markets of Santa Catarina, Ceará, Espírito Santo, Minas Gerais, Mato Grosso and Mato Grosso do Sul States. The traditional varieties will be originated from São Paulo (Vale do Ribeira and the north coast), Santa Catarina, Paraíba and Pernambuco states. Accessions from the ex situ germplasm collections from ESALQ/USP, Agronomic Institute (IAC) and FCA/UNESP will be assessed as well and with this, it is expected to promote the future formation of only one germplasm bank for common use. The protocol for DNA extraction and PCR (polymerase chain reaction) reactions will be optimized for D. alata. Twenty SSR primers will be tested for D. alata, with the selection of those which present better band resolution and polymorphism. Among the hypotheses formulated, it is possible to find a greater genetic diversity for microsatellites markers between D. alata landraces, with lower genetic diversity between commercial varieties. It is possible that the data confirm the existence of higher diversity within households and within geographic regions and that the landraces are not structure in space. There are few institutions currently involved with research related to the yam crop, being urgent the increment of studies and deeper research, to understand the factors which interfere with the species evolution, and how its genetic diversity is currently distributed.