Estrutura populacional e diversidade genética em cultivares tradicionais de mandioca-de-mesa do Paraná

• Autor(a) principal: Ortiz, Alex Henrique Tiene
• Data de Publicação: 2013
• Tipo de documento: Dissertação
• Idioma: por
• Título da fonte: Repositório Institucional da Universidade Estadual de Maringá (RI-UEM)
• Texto Completo: http://repositorio.uem.br:8080/jspui/handle/1/1388
• topic: Melhoramento genético - Plantas; Biologia molecular; Marcadores microssatelite - SSR; Mandioca - Diversidade genética; Ciências Agrárias; Agronomia

Sweet cassava can be found mainly in small farms named "backyard cultivations". In general, these cultivation systems maintain most of the available germplasm of the species, which genetic potential has not been enough studied. The evaluation of genetic variability in sweet cassava landraces can be done using both morpho-agronomic markers based in phenotype and molecular markers based on DNA (genotype). The objectives of this study were to evaluate the populational structure and the genetic diversity of sweet cassava landraces collected in "backyard cultivations" in the cities of Maringá, Cianorte and Toledo, in Parana State by using SSR molecular markers. All the analyzed loci were considered polymorphic and the average of alleles per locus was 3.15. The mean value of PIC of 0.4598 indicates that the primers were mostly considered moderately informative although the loci GA 126, GA 140, SSRY 13, SSRY 21, SSRY 45 and SSRY 101 were considered highly informative. The PIC values ranged from 0.5824 for GA 140 to 0.2646 for GA 21. In general the SSR loci were highly heterotic and presented high indexes of genetic diversity. The values of observed heterozygosity ranged from 0.0270 for GA 127 to 0.8718 for SSRY 45 with an average of 0.4762. The mean value of genetic diversity was 0.5407 ranging from 0.3138 for GA 21 to 0.6502 to GA 140. The most divergent combinations were: BGM 434T x BGM 20M, BGM 35C x BGM 20M, BGM 430T x BGM 232M, BGM 430T x BGM 164M, BGM 430T x BGM 322M and BGM 35C x BGM 164M. From these combinations the most recommended ones are those involving the accession BGM 20M which presented positive agronomic traits as resistence to bacterial blight and superelongation combined with flowering under the weather conditions of Maringá. The analysis of population structure revealed the occurrence of 4 groups among the sweet cassava landraces of the three localities. These results could be observed in all the methods used, as in the probabilistic method, as in the PCoA and the Neighbor-joining tree. The graphic dispersion of the points representing each of the landraces in PCoA allowed to observe the broad genetic diversity among the sweet cassava landraces. The parameters of Wright´s F statistics were determined using the the analysis of molecular variance. A variance of 11% among groups, 15% among individuals inside the groups and 74% among individuals in the whole population was observed. The Fis and Fit values, of 0.170 and 0.259 respectively, indicate a lack of heterozygotes in the population to reach the Hardy-Weinberg equilibrium, as inside groups as inside the whole population. The Fst value indicates a moderate differentiation among the groups. The genetic divertisy among sweet cassava landraces was considered high, and the groups that diverged the most were consisted mainly of individuals from Toledo and Maringá.