Variabilidade genética, morfométrica e germinativa em populações de Schizolobium parahyba (Vell.) Blake

Abstract

The aim of this work was to estimate the level and distribution of genetic variation within and among five Schizolobium parahyba (guapuruvu) populations and to evaluate the morphometric traits and dormancy of seeds of two populations of these species. The collect was carried out at coastal and mountain regions in the south of Rio de Janeiro. RAPD (Random Amplified Polymorphic DNA) markers were used in order to estimate the similarity of the genotypes and to indicate the genetic distance among individuals and populations. The following morphometric traits of seeds was assessed: width, lenght, thickness and weight. Variation in dormancy level was tested in seeds of two populations comparing the performance of scratching and not scratching seeds. Germination porcentage, germination and emergency speed index, normal seedling porcentage and death porcentage was assessed and compared among individual plant and populations by using ANOVA test. The polymorphic loco was 97%, as expected for a wide distributed specie. Of the total genetic diversity, 89% was atributtable to differences within populations and 11% to differences among populations, indicating a low amount of populations differentiation. The estimative of gene movement among populations revealed a high value (3,18 migrant per generation). Correlations among genetic and geographic distance were not found, indicating the lack of spatial structure of the specie. All morphometric traits differed significantly among individual within each of the population. The individuals plants from the mountain region presented the highest seed size. The major morphometric variation ocurred within population. The seed lenght responded with 60.87% of the total morphometric variation, followed by width (26,58%) and thickness (11,193%). Four groups were created by cluster analysis, with no origin relationship. Dormancy level differed significantly among and within populations and the highest dormancy level was presented by the coastal population. The germination speed index and death porcentage expressed better the dormancy levels than the other variables, differing significantly in the most of individuals trees. Seeds not scratched from mountain population presented better performance than the coastal one. Morphometrical and germination traits were not correlated. There were a high death percentage, specially for the scratched seeds. The role of biotics and abiotics factors in the selection of germination behavior are discussed based in the results and field observations.