Variabilidade genotípica e estrutura populacional de Astronium fraxinifolium Schott (Anacardiaceae) em área degradada de Cerrado
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Data
2019-04-29
Autores
Alcantara, Marcelo Augusto Mendes
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Universidade Estadual Paulista (Unesp)
Resumo
O Brasil possui vasta diversidade biológica tanto em sua fauna quanto em sua flora. Muito dessa diversidade ainda se encontra pouco ou inexplorada pela ciência. Dentre tantas espécies ainda pouco estudadas, encontra-se Astronium fraxinifolium Schott, popularmente conhecido como Gonçalo-Alves, tipicamente de cerrado e com aparições em outros biomas circundantes. A partir de uma população natural de A. fraxinifolium localizada em área degradada de Cerrado, o presente trabalho objetivou estimar a variação genotípica com base em seus caracteres silviculturais, propor um índice de seleção individual com base no valor genotípico (BLUP), determinar a proporção sexual dentro da população, o tamanho efetivo populacional, a diversidade, a estrutura genética, os níveis de endogamia, a coancestria e o tamanho efetivo populacional a partir da amplificação e identificação de locos microssatélites. A medição da altura foi realizada com equipamento hipsômetro baseado em sistema ultrassom e a estimativa do caráter diâmetro a altura do peito (DAP) a partir da conversão da circunferência à altura do peito. Para a extração do material genético e posterior genotipagem, coletou-se tecidos foliares de 384 árvores. As estimativas de componentes de variância e parâmetros genéticos dos caracteres silviculturais foram obtidos com base no procedimento - REML/BLUP empregando-se o software SELEGEN-REML/BLUP. A proporção sexual entre os indivíduos masculinos e femininos dentro da população foi estimada segundo o teste estatístico do qui-quadrado. A diversidade genética foi estimada utilizando o software FSTAT. Os coeficientes de coancestria e o erro padrão foram estimados utilizando o software SPAGeDi. A média geral para os caracteres altura e DAP foram de 11,31 m e 26,15 cm, respectivamente. A média desses caracteres para os indivíduos femininos e masculinos da população de regenerantes foram 11,67m e 23,92 cm e 10,91m e 25,72cm, respectivamente. Os valores para variância genotípica para o caráter DAP foram de 56,28 para a população, árvores femininas e masculinas de 57,89 e 48,10 respectivamente. A variância fenotípica por sua vez, indicou valores de 167,72 para a população e 99,59 e 173,18 para as subpopulações femininas e masculinas, respectivamente. O índice de seleção proposto para a população revelou ganhos de 17,36% para o caráter altura e 23,94% para o caráter DAP. A proporção sexual da população revelou ser de 1,13:1 (F:M) e encontra-se em equilíbrio de 1:1 de acordo com o teste do qui-quadrado (X2=0,21). Nos 386 genótipos de A. fraxinifolium observou-se 101 alelos. A média do número de alelos por loco foi de 5,08±1,2 e a estimativa média da riqueza alélica média (R) de 12,5±3,3. A heterozigosidade observada (Hˆo) foi significativamente menor do que a heterozigosidade esperada (He) em todos os locos. O nível médio de endogamia observada na população (F = 0,111) o que pode representar cruzamento entre meios-irmãos ( ) nos parentais. O coeficiente médio de coancestria entre as fêmeas ( f), machos e fêmeas ( fm), e machos ( m) foram de 0,000032; 0,000365 e 0,001776, respectivamente. A coancestria média do grupo de árvores dentro da população foi baixa e positiva ( = 0,002174). A partir destes dados, é possível inferir que a população de A. fraxinifolium presente na área degradada, antiga área de empréstimo da UHE Ilha Solteira apresenta diversidade genética significativa com alto potencial evolutivo e de manutenção da diversidade genética ao longo das gerações, selecionável para compor populações base de melhoramento genético, bem como banco ativo de germoplasma e outras coleções de germoplasma (sementes).
Brazil has a vast biological diversity both in its fauna and flora. Much of this diversity is still little or unexplored by science. Among so many species still poorly studied, there is Astronium fraxinifolium Schott, popularly known as Gonçalo-Alves, typically a Cerrado specie with appearances in other surrounding biomes. From a natural population of A. fraxinifolium located in a degraded area of Cerrado, the present work aimed to estimate genotypic variation based on its silvicultural characters, propose an individual selection index based on genotypic value (BLUP), determine the sexual ratio in the population, effective population size, diversity, genetic structure, inbreeding levels, coancestry, and effective population size from the amplification and identification of microsatellite loci. Height measurement was performed using an ultrasound-based hypsometer device and the diameter-to-chest height (DBH) character estimate from the circumference to chest height conversion. For the extraction of genetic material and subsequent genotyping, we collected leaf tissues from 384 trees. Estimates of variance components and genetic parameters of silvicultural characters were obtained based on the procedure - REML / BLUP using the software SELEGEN-REML / BLUP. The sex ratio between male and female individuals in the population was estimated according to the chi-square statistical test. The genetic diversity was estimated using FSTAT software. The coancestry coefficients and standard error were estimated using SPAGeDi software. The overall average for the characters height and DBH were 11.31 m and 26.15 cm, respectively. The average of these characters for female and male individuals of the population were 11.67 m and 23.92 cm, and 10.91 m and 25.72 cm, respectively. The values for genotypic variance for the DBH character were 56.28 for the population and for female and male trees 57.89 and 48.10 respectively. The phenotypic variance in turn indicated values of 167.72 for the population and 99.59 and 173.18 for the female and male subpopulations, respectively. The selection index proposed for the population revealed gains of 17.36% for the height character and 23.94% for the DBH character. The sex ratio of the population was 1.13: 1 (F: M) and is in a 1: 1 equilibrium according to the chi-square test (X2 = 0.21). In the 386 genotypes of A. fraxinifolium, 101 alleles were observed. The average number of alleles per locus was 5.08 ± 1.2 and the average estimate of the allelic richness (R) was 12.5 ± 3.3. The observed heterozygosity (Hˆo) was significantly lower than the expected heterozygosity (He) in all loci. The average level of inbreeding observed in the population (F = 0.111) which may represent cross-sectional crossing ( ) in the parents. The mean coefficient of coancestry between females ( f), males and females ( fm), and males ( m) was 0.000032; 0.000365 and 0.001776, respectively. The coancestry mean of the group tree within the population was low and positive ( = 0.002174). From these data, it is possible to infer that the population of A. fraxinifolium present in the degraded area, former borrow area of Ilha Solteira HPP presents significant genetic diversity with high evolutionary potential and maintenance of the genetic diversity throughout generations, selectable to compose breeding base populations, as well as active germplasm bank and other germplasm collections (seeds).
Brazil has a vast biological diversity both in its fauna and flora. Much of this diversity is still little or unexplored by science. Among so many species still poorly studied, there is Astronium fraxinifolium Schott, popularly known as Gonçalo-Alves, typically a Cerrado specie with appearances in other surrounding biomes. From a natural population of A. fraxinifolium located in a degraded area of Cerrado, the present work aimed to estimate genotypic variation based on its silvicultural characters, propose an individual selection index based on genotypic value (BLUP), determine the sexual ratio in the population, effective population size, diversity, genetic structure, inbreeding levels, coancestry, and effective population size from the amplification and identification of microsatellite loci. Height measurement was performed using an ultrasound-based hypsometer device and the diameter-to-chest height (DBH) character estimate from the circumference to chest height conversion. For the extraction of genetic material and subsequent genotyping, we collected leaf tissues from 384 trees. Estimates of variance components and genetic parameters of silvicultural characters were obtained based on the procedure - REML / BLUP using the software SELEGEN-REML / BLUP. The sex ratio between male and female individuals in the population was estimated according to the chi-square statistical test. The genetic diversity was estimated using FSTAT software. The coancestry coefficients and standard error were estimated using SPAGeDi software. The overall average for the characters height and DBH were 11.31 m and 26.15 cm, respectively. The average of these characters for female and male individuals of the population were 11.67 m and 23.92 cm, and 10.91 m and 25.72 cm, respectively. The values for genotypic variance for the DBH character were 56.28 for the population and for female and male trees 57.89 and 48.10 respectively. The phenotypic variance in turn indicated values of 167.72 for the population and 99.59 and 173.18 for the female and male subpopulations, respectively. The selection index proposed for the population revealed gains of 17.36% for the height character and 23.94% for the DBH character. The sex ratio of the population was 1.13: 1 (F: M) and is in a 1: 1 equilibrium according to the chi-square test (X2 = 0.21). In the 386 genotypes of A. fraxinifolium, 101 alleles were observed. The average number of alleles per locus was 5.08 ± 1.2 and the average estimate of the allelic richness (R) was 12.5 ± 3.3. The observed heterozygosity (Hˆo) was significantly lower than the expected heterozygosity (He) in all loci. The average level of inbreeding observed in the population (F = 0.111) which may represent cross-sectional crossing ( ) in the parents. The mean coefficient of coancestry between females ( f), males and females ( fm), and males ( m) was 0.000032; 0.000365 and 0.001776, respectively. The coancestry mean of the group tree within the population was low and positive ( = 0.002174). From these data, it is possible to infer that the population of A. fraxinifolium present in the degraded area, former borrow area of Ilha Solteira HPP presents significant genetic diversity with high evolutionary potential and maintenance of the genetic diversity throughout generations, selectable to compose breeding base populations, as well as active germplasm bank and other germplasm collections (seeds).
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Áreas degradadas, Cerrado, estrutura genética, população natural, degraded areas, , genetic structure, natural population