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  • Author: V.A. Sousa x
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Variation and Population Structure at Enzyme Gene Loci in Araucaria angustifolia (Bert.) O. Ktze

Abstract

We describe alloenzyme variation in A. angustifolia populations of three separate geographical areas in southern Brazil. The genetic structure of populations was examined in seedtrees, embryos and effective pollen. Seven out of 24 enzyme loci were polymorphic. The average number of alleles per locus (24 loci) was 1.54, with 2.44 alleles per polymorphic locus. Mean expected and observed heterozygosities at the polymorphic loci were He = 0.128 and Ho = 0.132 for seed-trees, and He = 0.142 and Ho = 0.161 for embryos. All measures of genetic variability were highest in the most northern populations. Differences among localities explained 84.14% and 92.06% of the total genetic diversity in embryos and seed trees, respectively. Sex ratio was 1:1 in almost all populations. Female and male gene pools differed in allele frequencies, most significantly at loci 6- Pgdh-B and Skdh-B. This explains the excess of heterozygotes detected among embryos. No inbreeding or excess of heterozygotes was detected among adult seed trees. Genetic variation in A. angustifolia revealed a latitudinal gradient.

Open access
Adaptability, stability, productivity and genetic parameters in slash pine second-generation families in early age

Abstract

The study was conducted to estimate the stability, adaptability, productivity and genetic parameters in Slash pine second-generation half-sib families, considering phenotypic traits in early age. Forty-four families from a first generation seed orchard in Colombo-PR, Brazil, were used in this study. Two progenies tests were established in a randomized complete block design. The first test was implemented in March 2009 in Ribeirão Branco, São Paulo state, containing 40 blocks, one tree per plot, 44 treatments (progenies) and 6 controls. Another test was implemented in Ponta Grossa, Paraná state, using the same experimental design and number of plants per plot, and with 24 treatments, 32 blocks. The growth traits evaluated were total height, diameter at breast height (dbh) and wood volume, within five years. The form traits evaluated were stem form, branch thickness, branch angle, number of branches, fork and fox tail five years after planting. Deviance analysis and estimates of stability, adaptability, productivity and genetic parameters were performed using the methods of best linear unbiased predictor (BLUP) and residual maximum likelihood (REML). There was significant variation among progenies for growth and form traits. Considerable genetic variation was detected mainly for wood volume. High coefficients of genetic variation and heritability showed low environmental influence on phenotypic variation, which is important for the prediction of genetic gain by selection. Crosses between different progenies individuals groups will be prioritized for obtaining heterotics genotypes and increase the probability of obtaining high specific combining ability.

Open access