Astyanax fishes are among the most important food-web components of South America rivers. In the Iguaçu River basin, the Astyanax genus is represented mainly by endemic species. For millions of years, that hydrographic basin has been geographically isolated from the Paraná River basin by the Iguaçu Falls. Recently, a species from the Upper Paraná River basin identified as Astyanax bimaculatus was revised and described as a new species named Astyanax altiparanae Garutti & Britski, 2000. Fauna endemism and geographic isolation triggered interest in investigations to evaluate the identification and genetic relatedness among two A. altiparanae populations from the Upper Paraná River basin and the population identified as A. bimaculatus in the Iguaçu River, upstream from the Iguaçu Falls. Mitochondrial DNA sequences and RAPD markers revealed high genetic diversity within each population, as well as low genetic distance, high gene flow, and high mitochondrial DNA similarity among all three populations. In conjunction with morphological similarities, these results demonstrated that the population presently known as Astyanax bimaculatus in the Iguaçu River should actually be stated as Astyanax altiparanae. Furthermore, it could be inferred that the A. altiparanae population is not endemic and most likely it was recently introduced in the Iguaçu River basin, maintaining the ancestral genetic identity.
A new viviparous mutant of maize (Zea mays L.), associated with genetic instability and designated viviparous-12 (vp12), was identified in a synthetic Tuxpeño adapted to tropical regions. In the present work, the linkage group of this new locus was determined. Progenies of inbred line L477 segregating for the vp12 mutant were crossed with waxy-marked reciprocal translocation stocks. The phenotypic frequencies of the wx and vp12 mutants were analyzed in F2 progenies. The results demonstrated that the Viviparous-12 locus of maize is located on the long arm of chromosome 6.
Mutantes vivíparos em milho têm sido alvo de interesse para estudos de regulação dos processos de desenvolvimento e maturação da semente. Um novo mutante vivíparo de milho, associado com instabilidade genética e denominado vivíparo-12 (vp12), foi identificado em sintético Tuxpeño adaptado a regiões tropicais. No presente trabalho, o grupo de ligação desse novo loco foi determinado. Progênies da linhagem endogâmica de milho L477 segregantes para o mutante vp12 foram cruzadas com estoques de translocações recíprocas marcadas com o mutante de endosperma waxy. As freqüências fenotípicas dos mutantes wx e vp12 foram analisadas nas progênies F2. Os resultados demonstraram que o loco Vivíparo-12 de milho está localizado no braço longo do cromossomo 6.