Diversidade genética em população de melhoramento de mogno africano (Khaya ivorensis A. Chev.)
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2014-08-04
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Universidade Federal de Goiás
Resumo
The strong demand for hardwood drives selective logging and degradation of
forests ecossystems in Brazil. Due to its wood value and predatory logging, Brazilian
mahogany (Swietenia macrophylla) is at risk of extinction. Currently, its trees are protected
and banned from logging by the Brazilian Institute of Environment (IBAMA).
Monoculture of the Brazilian mahogany is proven unsuccessful due to the attack of the
Hypsipyla grandella larvae. An alternative to Brazilian mahogany plantation is the African
mahogany (Khaya ivorensis), a species with similar high valued wood properties. The
Universidade Federal de Goiás in partnership with Mudas Nobres Company started a
breeding program with Khaya ivorensis. The objective of this study was to evaluate the
genetic diversity and divergence among 53 superior trees selected and cloned as part of the
breeding strategies. Clones were selected from three different populations, planted in two
farms in Pará state and originating from Ivory Coast and Tanzania populations. Twelve
seedlings of Khaya senegalensis were also used as a control group in the analyses of
genetic divergence. The individuals were genotyped with eight microsatellite loci
developed for K. senegalensis, by capillary electrophoresis on the ABI-3100 (Applied
Biosystems) platform. The software GeneMapper (Applied Biosystems) was used to
genotype the alleles. The average number of alleles per locus was 5.875. The average
expected heterozygosity was lower (HE = 0.563) than the average observed heterozygosity
(HO = 0.738). Therefore, the average intrapopulation fixation index was negative (f = -
0.314) indicating that high inbreeding depression is decreasing the frequency of
homozygous when compared to what would be expected under Hardy-Weinberg
Equilibrium. The average fixation index between populations was estimated at θ = 0.008,
indicating that only 0.8% of the genetic variability is due to differences between
populations. The dendrogram generated from the matrix of Rogers’ genetic distance
showed two distinct groups, separating the control group with K. senegalensis from the K.
ivorensis selected trees. The group composed of K. ivorensis had nodes with weak
bootstrap consistency indicating weak genetic structure among selected trees. The lack of
genetic structure was confirmed by a Bayesian approach on the Structure (version 2.3.4)
program. The genetic diversity observed within the selected breeding population is
comparable to that of natural populations of African and Brazilian mahoganies. The
genetic distance estimated with this work will guide the selection of divergent progenitors
to be crossed.
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SOARES, Sabrina Delgado. Diversidade genética em população de melhoramento de mogno africano (Khaya ivorensis A. Chev.). 2014. 69 f. Dissertação (Mestrado em Genética e Biologia Molecular) - Universidade Federal de Goiás, Goiânia, 2014.