Morphological variation and isozyme diversity in Dioscorea alata L. landraces from Vale do Ribeira, Brazil

Abstract

Traditional growers of the Vale do Ribeira, São 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 São Paulo State, contributing for the in situ/on farm conservation of this crop.

Genetic structure and diversity in the Dioscorea cayenensis/D. rotundata complex revealed by morphological and isozyme markers

“…The enzymes were extracted from recently expanded leaves (200 mg) from adult plants (6-8 months), and the procedures were performed according to Bressan et al (2011). Six systems were used with polyacrylamide gels: glucose-6-phosphate isomerase (GPI; E.C.…”

“…Previous research was carried out using morphological and isozyme analysis to study the genetic diversity of local varieties of D. alata L. that were cultivated by traditional farmers in Vale do Ribeira (Bressan et al, 2011). In Africa, the species complex D. cayenensis/D.…”

Morphological diversity and identification key for landraces of the Amerindian yam in central Amazon

“…In order to perform a cluster analysis, we opted for the transformation of the morphological characteristics into binary data (presence, absence) (Bressan et al, 2011), which allowed of the similarity estimation through the Jaccard index. Based on the similarity matrix, a cluster analysis was applied by the UPGMA method (unweighted pair-group method using arithmetic mean) using the FDiversity statistical software program (Casanoves et al, 2011).…”

Distribution, management and diversity of yam local varieties in Brazil: a study on Dioscorea alataL.

“…Monteiro and Peressin (2002) pointed out that flowering of the species is rare in Brazil. Bressan et al (2011) reported flowering in only 8.6% from a total of 35 D. alata accessions grown under experimental conditions in Piracicaba, São Paulo, and no seed was produced from the flowering plants. Lebot (2009) states that unfortunately, and in most cases, the varieties that have the best features, whether agronomic (compact tubers, for example) or palatability characteristics, are those that do not flower.…”

“…This study also showed that there is a clear regionalization in the assignment of popular names for D. alata local varieties, according to their morphology, uses or origin. The role of farmers in maintaining the local agro-biodiversity, whether in home gardens or fields, is important for the maintenance of the genetic diversity of yams and other crops over generations (Chair et al, 2010;Siqueira et al, 2010;Bressan et al, 2011;Veasey et al, 2012). However, for these varieties to be maintained at an on farm conservation basis, agroecological conservation policy goals must be considered, as well as more studies emphasising the importance of yams in rural areas.…”