Abstract
Traditional growers of the Vale do Ribeira, Sao Paulo State, grow and make use of several D. alata landraces. This study assessed the genetic diversity of 16 landraces, using isozymatic and morphological markers and comparing them with 19 commercial varieties of D. alata. Their distribution in different levels of organization such as households and communities of the Vale do Ribeira was evaluated. Isozymatic analyses were performed with polyacrylamide (six systems) and starch gels (one system), while the morphological analyses were carried out with 24 traits. Due to the polyploid nature of this species, the isozymatic bands were scored as binary data. Morphological traits were also scored as binary data. Principal coordinates and cluster analyses were conducted for both markers, using for the later the Jaccard´s similarity coefficient and UPGMA method. The separation of the landraces from the commercial varieties, which showed lower genetic diversity, was reported for both markers. No correlation between genetic and geographical distances was found for both data, which suggests that the observed variability is not spatially structured. Also, no correlation was found between both markers. The analysis of molecular variance (AMOVA) indicated that genetic diversity was mainly found within households for both isozymatic (54%) and morphological (70%) markers. The results obtained for both markers revealed the importance of traditional agriculturists in the Vale do Ribeira in maintaining high diversity for D. alata, even higher than the varieties commercialized in Sao Paulo State, contributing for the in situ/on farm conservation of this crop.
Highlights
Yam (Dioscorea spp.) is a horticulture crop with expressive world consumption, especially in developing countries
The superoxide dismutase (SOD) system showed the highest number of bands (13) followed by PGI and malate dehydrogenase system (MDH) with 12, GOT with 10, glucose-6-phosphote dehydrogenase (G6PDH) with 9, SKDH with 8 and PGM with 7, in a total of 71 bands for all systems
The cluster analysis classified the 35 D. alata accessions into six groups, distributed as following: I; II; III; IV; V; and VI (Figure 2)
Summary
Yam (Dioscorea spp.) is a horticulture crop with expressive world consumption, especially in developing countries. The isozymatic genetic characterization in D. alata was performed by Lebot et al (1998) and Twyford (1990) This species was studied with molecular markers such as RAPD, for the evaluation of resistance to anthracnose (Mignouna et al, 2002a) and genetic diversity studies (Asemota et al., 1996; Cheng and Liu, 1996; Zannou et al, 2009); AFLP, for the study of intraspecific genetic diversity (Egesi et al, 2006; Malapa et al, 2005) and development of a genetic map and analysis of QTL aimed at resistance to anthracnose (Mignouna et al, 2002b). Arnau et al (2009) used six microsatellite primers to study the segregation patterns from four different progenies of D. alata
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