Development of retrotransposon-based markers IRAP and REMAP for cassava (Manihot esculenta)

Retrotransposons are abundant in the genomes of plants. In the present study, inter-retrotransposon amplified polymorphism (IRAP) and retrotransposon-microsatellite amplified polymorphism (REMAP) markers were developed for the cassava genome (Manihot esculenta Crantz). Four cassava cultivars (Fécula Branca, IPR-União, Olho Junto, and Tamboara, two samples per cultivar) were used to obtain IRAP and REMAP fingerprints. Twelve designed primers were amplified alone and in combinations. The 42 IRAP/REMAP primer combinations amplified 431 DNA segments (bands; markers) of which 36 (8.36%) were polymorphic. The largest number of informative markers (16) was detected using the primers AYF2 and AYF2xAYF4. The number of bands for each primer varied from 3 to 16, with an average of 10.26 amplified segments per primer. The size of the amplified products ranged between 100 and 7000 bp. The AYF2 primer generated the highest number of amplified segments and showed the highest number of polymorphic bands (68.75%). Two samples of each cassava cultivar were used to illustrate the usefulness and the polymorphism of IRAP/REMAP markers. IRAP and REMAP markers produced a high number of reproducible bands, and might be informative and reliable for investigation of genetic diversity and relationships among cassava cultivars

Esterase polymorphism in remanant populations of Aspidosperma polyneuron Müll.Arg. (Apocynaceae) Polimorfismo de esterases em populações remanescentes de Aspidosperma polyneuron Müll.Arg. (Apocynaceae)

The population genetic structure of the endangered tree species Aspidosperma polyneuron Mull.Arg. (Apocynaceae) was reported based on analysis of esterase polymorphism in two remanant populations. Allelic variation was detected at three isoesterase loci (Est-3, Est-9, and Est-10). The proportion of polymorphic loci for both populations was 30% and deviation from Hardy-Weinberg equilibrium was observed for the Est-3 locus observed in the northern population. Segregation distortion and the lower level of observed and expected heterozygosity in this population were attributed to founder genotype. The high genetic identity values for northern and northwestern populations are in accordance with the low levels of interpopulation genetic divergence demonstrated by the F(ST) (0.03) value. The F(IS) value (0.23) indicated moderate levels of inbreeding. A. polyneuron can be indicated as an example of endangered species suggesting high genetic variation in contrast to the low genetic variation reported for endangered species. The esterase isozymes may be a good genetic marker for studies of natural A. polyneuron populations.<br>A análise do polimorfismo de isozimas esterases foi usada para reportar a estrutura genética de duas populações remanecentes da espécie de árvore em extinção Aspidosperma polyneuron Müll.Arg. (Apocynaceae). Variação alélica foi detectada em três locos de isoesterases (Est-3, Est-9, e Est-10). A proporção de locos polimórficos de ambas as populações foi de 30%, sendo observado um desvio do equilíbrio de Hardy-Weinberg no loco Est-3 na população da região norte do Estado do Paraná. Uma distorção na segregação e um mais baixo nível de heterozigosidade observada e esperada nesta população foram atribuídos ao efeito do genótipo fundador. Os valores altos de identidade genética das populações do norte e noroeste do Estado estão de acordo com o baixo nível de divergência genética interpopulacional demonstrado pelo valor de F(ST) (0,03). O valor de F(IS) (0,23) indicou moderado nível de endocruzamentos. A. polyneuron pode ser indicada como um exemplo de espécie em extinção apresentando variação genética alta, contrastando com a variação genética baixa reportada sobre espécies em extinção. As isozimas esterases podem ser um bom marcador genético em estudos de populações naturais de A. polyneuron