Divergência genética entre plantas matrizes e estresses hídrico e salino na germinação de sementes de Cordia trichotoma (Vell.) Arráb. ex Steud.
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Data
2021-06-17
Autores
Souza, João Vitor Oliveira de
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Universidade Estadual Paulista (Unesp)
Resumo
Cordia trichotoma é uma espécie arbórea que apresenta potencial para diversos usos econômicos, principalmente de sua madeira, além de ser recomendada para reflorestamentos com finalidade ambiental e, embora produza sementes com abundância, poucos estudos foram realizados sobre a variabilidade e a divergência genética da espécie, bem como a tolerância a estresses abióticos durante o processo germinativo de sementes e desenvolvimento inicial de plântulas. Portanto, objetivou-se, primeiramente, avaliar a variabilidade e a divergência genética da espécie com base nos caracteres de sementes e plântulas e, posteriormente, a tolerância aos estresses hídrico e salino no processo germinativo. No estudo da variabilidade e divergência genética, sementes de 32 árvores matrizes de C. trichotoma foram submetidas a avaliações biométricas, ao teste padrão de germinação e desenvolvimento de plântulas e ao teste de condutividade elétrica. Os parâmetros genéticos foram estimados via REML/BLUP e, a partir dos valores genotípicos, foi obtida a correlação entre caracteres e avaliada a divergência genética entre as matrizes pelos métodos de agrupamento de Ward, “k-means” e pela análise de componentes principais. No estudo da tolerância aos estresses abióticos, um lote com a mistura das sementes das árvores matrizes foi submetido ao teste de germinação nas temperaturas de 25 °C e 30 °C, simulando o estresse hídrico mediado por PEG 6000 nos potenciais de 0 (controle), -0,1, -0,2, -0,4 e -0,6 MPa, e o estresse salino mediado por NaCl nos potenciais de 0 (controle), -0,1, -0,2, -0,4, -0,6 e -0,8 MPa. Foram avaliados caracteres de germinação e vigor de sementes e plântulas. No primeiro estudo, obtiveram-se valores elevados de herdabilidade da média de genótipos (0,562 a 0,994), acurácia da seleção (0,749 a 0,997) e coeficiente de variação genotípica (7,39% a 44,63%), com coeficientes de variação relativa acima de 1,0 (1,14 a 5,71), exceto para comprimento da parte aérea de plântulas (0,51). Sementes maiores correlacionaram-se com plântulas de maior massa e o desempenho germinativo correlacionou-se com o tamanho inicial das plântulas. As matrizes foram separadas em três grupos pelos métodos de agrupamento e a análise de componentes principais corroborou os agrupamentos formados, com 85,7% da variância total dos dados explicada nos três primeiros componentes. A divergência foi moderada, mas é possível selecionar árvores matrizes para melhoramento genético ou conservação da espécie. No segundo estudo, concluiu-se que as sementes da espécie apresentam baixa tolerância aos estresses, tendo a germinação totalmente inibida sob potencial hídrico de -0,4 MPa quando submetida a estresse hídrico e a -0,8 MPa sob estresse salino.
Cordia trichotoma is a tree species that has potential for several economic uses, mainly from wood, besides being recommended for reforestation for environmental purposes and, although it produces seeds in abundance, few studies have been carried out on the variability and genetic divergence of the species, as well as the tolerance to abiotic stresses during the seed germination process and initial seedling development. Therefore, the objective was, first, to evaluate the variability and genetic divergence of the species based on seed and seedling traits and, later, the tolerance to water and salt stress in the germination process. In the study of genetic variability and divergence, seeds of 32 mother trees of C. trichotoma were subjected to biometric evaluations, the standard test of germination and seedling development and the electrical conductivity test. The genetic parameters were estimated via REML/BLUP and, from the genotypic values, the correlation between traits was obtained and the genetic divergence between the mother trees was evaluated by Ward's and “k-means” grouping methods, and by the principal component analysis. In the study of tolerance to abiotic stresses, a seed lot with the mixture of the seeds of the mother trees was submitted to the germination test at temperatures of 25 °C and 30 °C, simulating the water stress mediated by PEG 6000 at the potentials of 0 (control), -0.1, -0.2, -0.4 and -0.6 MPa, and the salt stress mediated by NaCl at the potentials of 0 (control), -0.1, -0.2, -0.4, -0.6 and -0.8 MPa. Germination traits and seedling vigor were evaluated. In the first study, high values of heritability were obtained for the mean of genotypes (0.562 to 0.994), accuracy of selection (0.749 to 0.997) and coefficient of genotypic variation (7.39% to 44.63%), with coefficients of relative variation above 1.0 (1.14 to 5.71), except for length of shoot of seedlings (0.51). Larger seeds correlated with seedlings of greater mass and the germinative performance correlated with the initial size of the seedlings. The mother trees were separated into three groups by grouping methods and the principal component analysis corroborated the formed groups, with 85.7% of the total data variance explained in the first three components. The divergence was moderate, but it is possible to select trees for genetic improvement or conservation of the species. In the second study, it was concluded that the seeds of the species have a low tolerance to stress, and the germination was completely inhibited under water potential of -0.4 MPa when subjected to water stress and -0.8 MPa under salt stress.
Cordia trichotoma is a tree species that has potential for several economic uses, mainly from wood, besides being recommended for reforestation for environmental purposes and, although it produces seeds in abundance, few studies have been carried out on the variability and genetic divergence of the species, as well as the tolerance to abiotic stresses during the seed germination process and initial seedling development. Therefore, the objective was, first, to evaluate the variability and genetic divergence of the species based on seed and seedling traits and, later, the tolerance to water and salt stress in the germination process. In the study of genetic variability and divergence, seeds of 32 mother trees of C. trichotoma were subjected to biometric evaluations, the standard test of germination and seedling development and the electrical conductivity test. The genetic parameters were estimated via REML/BLUP and, from the genotypic values, the correlation between traits was obtained and the genetic divergence between the mother trees was evaluated by Ward's and “k-means” grouping methods, and by the principal component analysis. In the study of tolerance to abiotic stresses, a seed lot with the mixture of the seeds of the mother trees was submitted to the germination test at temperatures of 25 °C and 30 °C, simulating the water stress mediated by PEG 6000 at the potentials of 0 (control), -0.1, -0.2, -0.4 and -0.6 MPa, and the salt stress mediated by NaCl at the potentials of 0 (control), -0.1, -0.2, -0.4, -0.6 and -0.8 MPa. Germination traits and seedling vigor were evaluated. In the first study, high values of heritability were obtained for the mean of genotypes (0.562 to 0.994), accuracy of selection (0.749 to 0.997) and coefficient of genotypic variation (7.39% to 44.63%), with coefficients of relative variation above 1.0 (1.14 to 5.71), except for length of shoot of seedlings (0.51). Larger seeds correlated with seedlings of greater mass and the germinative performance correlated with the initial size of the seedlings. The mother trees were separated into three groups by grouping methods and the principal component analysis corroborated the formed groups, with 85.7% of the total data variance explained in the first three components. The divergence was moderate, but it is possible to select trees for genetic improvement or conservation of the species. In the second study, it was concluded that the seeds of the species have a low tolerance to stress, and the germination was completely inhibited under water potential of -0.4 MPa when subjected to water stress and -0.8 MPa under salt stress.
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Palavras-chave
Florestas tropicais, Análise multivariada, Variação genética, Desidratação (Hídrica)