BackgroundThe advent of high-throughput genotyping technologies coupled to genomic prediction methods established a new paradigm to integrate genomics and breeding. We carried out whole-genome prediction and contrasted it to a genome-wide association study (GWAS) for growth traits in breeding populations of Eucalyptus benthamii (n =505) and Eucalyptus pellita (n =732). Both species are of increasing commercial interest for the development of germplasm adapted to environmental stresses.ResultsPredictive ability reached 0.16 in E. benthamii and 0.44 in E. pellita for diameter growth. Predictive abilities using either Genomic BLUP or different Bayesian methods were similar, suggesting that growth adequately fits the infinitesimal model. Genomic prediction models using ~5000–10,000 SNPs provided predictive abilities equivalent to using all 13,787 and 19,506 SNPs genotyped in the E. benthamii and E. pellita populations, respectively. No difference was detected in predictive ability when different sets of SNPs were utilized, based on position (equidistantly genome-wide, inside genes, linkage disequilibrium pruned or on single chromosomes), as long as the total number of SNPs used was above ~5000. Predictive abilities obtained by removing relatedness between training and validation sets fell near zero for E. benthamii and were halved for E. pellita. These results corroborate the current view that relatedness is the main driver of genomic prediction, although some short-range historical linkage disequilibrium (LD) was likely captured for E. pellita. A GWAS identified only one significant association for volume growth in E. pellita, illustrating the fact that while genome-wide regression is able to account for large proportions of the heritability, very little or none of it is captured into significant associations using GWAS in breeding populations of the size evaluated in this study.ConclusionsThis study provides further experimental data supporting positive prospects of using genome-wide data to capture large proportions of trait heritability and predict growth traits in trees with accuracies equal or better than those attainable by phenotypic selection. Additionally, our results document the superiority of the whole-genome regression approach in accounting for large proportions of the heritability of complex traits such as growth in contrast to the limited value of the local GWAS approach toward breeding applications in forest trees.Electronic supplementary materialThe online version of this article (doi:10.1186/s12864-017-3920-2) contains supplementary material, which is available to authorized users.

In this study, the breeding perspectives of 41 open-pollinated progenies of Eucalyptus grandis were evaluated based on their wood traits. The progenies were distributed in two experiments in a randomized complete block design, with three replicates and linear plots containing six plants each. The traits were assessed at eight years of age. Two trees from each plot were selected for this assessment based on better growth, stem form and phytosanity. Significant differences in basic density, sapwood/heartwood ratio, bowing, specific gravity, parallel compression and static bending were detected among the progenies. These traits were potentially promising for breeding programs, with heritability coefficients that varied from 0.34 to 0.61 on a progeny mean basis. There was no genetic variation in the moisture content, board end-splitting, log volume under the bark, log eccentricity, bark content, crooking, and shear strength of the progenies. Intermediate to highly significant genetic correlations were detected among the physical and mechanical properties, as well as between pairs of traits such as basic density and log end-splitting, basic density and bowing, specific gravity and bowing, sapwood/heartwood ratio and bowing, log volume and bowing, and log volume and log end-splitting. These results show that the levels of growth stress in trees can be reduced by selection using indirect traits such as the sapwood/heartwood ratio and bowing.

The aim of this study was to evaluate Eucalyptus badjensis concerning the genetic variation for growth traits and the potential of the species in supporting a breeding programme. The field trial was a provenance/progeny test established in Campina da Alegria, Santa Catarina, Brazil (latitude 26°52′05.1″ S, longitude 51°48′47.5″ W, altitude 1,015 m) in a soil classified as Latossolic Alumino-Ferric Brown Nitosol. The experiment comprised 60 open-pollinated progenies from the provenances Glenbog and Badja State Forest, New South Wales, Australia. Ten replicates and plots with six plants in row were used. At the age of 17 years, 279 trees were assessed for diameter of the bole at breast height (DBH), total tree height (H) and volume of wood with bark (Vol). After submitting the data to statistical genetic analysis, the overall means for DBH, H and Vol were 45.17 cm, 33.30 m and 2.84 m3, and the estimates of additive coefficient of variation [CV^a(%)] were 12.59%, 5.91% and 26.51%, respectively. Heritability coefficients of additive effects (trueh^a2) were also estimated and the following values were found: 0.443, 0.312 and 0.358. Thirty-nine trees from 25 different progenies were selected. The expected means of the provenances after improvement were 50.02 cm, 34.35 m and 3.47 m3 for DBH, H and Vol, respectively.

Resumo-Com objetivo de avaliar o desempenho de clones comerciais de eucalipto na região de Ponta Porã, MS, foram instalados dois testes clonais de eucalipto em 2009. Cada experimento foi composto por cinco clones (AEC 144, AEC 224, GG 100, 58 e COP 1277) e três testemunhas seminais (Eucalyptus grandis, Eucalyptus urophylla e Eucalyptus urophylla x Eucalyptus grandis). Os experimentos foram instalados em blocos casualizados, com quatro repetições, parcelas quadradas de 25 plantas (Ensaio 1) e 16 plantas (Ensaio 2), em espaçamento de 3 m x 3 m. Aos 51 meses foram mensuradas: circunferência à altura do peito e altura. A partir dessas informações foi estimado o volume de madeira por árvore. Realizou-se também avaliação fenotípica com base em características silviculturais. Os clones AEC 144 e AEC 224 apresentaram as maiores estimativas de volume de madeira. O uso desses clones em plantios comerciais deve proporcionar bons níveis de produtividade, desde que aplicadas adequadas técnicas silviculturais.

ResumoO presente trabalho teve por objetivos desenvolver e aplicar, no oeste catarinense, uma metodologia de estabelecimento de unidades de manejo para pinus a partir do mapeamento semi-detalhado de solos das áreas de estudo. Duas hipóteses de trabalho foram modeladas, ambas utilizando o sistema de produção de pinus local, que não faz correção da deficiência de nutrientes (ΔN): uma interpretação baseada na ausência de resposta ao melhoramento do ΔN, ou seja, que os tetos de produtividade independem dessa ação, sendo esse o modelo atual; e uma segunda interpretação considerando que a ausência do melhoramento do ΔN interfere nos tetos de produtividade do cultivo de pinus para as terras estudadas, modelo que representa um novo paradigma a ser testado. Cada polígono do mapa de solos detalhado foi associado a uma base de dados, que permitiu a definição dos graus de limitação das terras (ΔN, deficiência de água, deficiência de oxigênio, suscetibilidade à erosão e impedimentos ao manejo) para o cultivo do pinus. Conjuntos de critérios, considerando os diferentes graus de limitação alcançados para cada faixa de terra (polígonos do mapeamento de solos), definiram os guias para as classes de unidades de manejo para o cultivo de pinus. O mapeamento de solos semi-detalhado das áreas de produção identificou áreas mapeáveis associadas às classes de solos, em nível de ordem, Latossolos, Nitossolos, Cambissolos, Neossolos e Gleissolos. Essas cinco ordens geraram 36 unidades de mapeamento de solos. As limitações associadas aos atributos profundidade efetiva, relevo e presença de pedregosidade/rochosidade fizeram dos impedimentos ao manejo os fatores de limitação mais importantes para o cultivo de pinus das áreas mapeadas. Os quantitativos das classes de unidades de manejo para pinus dependeram de se considerar ou não a hipótese de resposta ao melhoramento do ΔN no sistema de manejo em uso na região. Na hipóte-se da ausência de resposta ao melhoramento do ΔN para a produção de pinus, temos os seguintes quantitativos: Apta superior com 113,14 ha (ou 7,5% da área mapeada); Apta inferior com 644,73 (ou 42,8% da área mapeada); Marginal superior com 408,35 (ou 27,1% da área mapeada); Marginal inferior com 277,58 ha (ou 18,4% da área mapeada) e Inapta com 63,2 ha (ou 4,2% da área mapeada). Ao se considerar a hipótese de uma resposta positiva ao melhoramento de ΔN para a produção de pinus e que o atual sistema de manejo não faz esse melhoramento, ocorre uma piora dos resultados, com muitas terras migrando das classes de unidades de manejo Apta (superior e inferior) para a classe Marginal superior.Palavras-chave: levantamento de solos, aptidão silvicultural, planejamento de uso da terra. AbstractThis study was carried out in order to develop and implement an enhanced methodology for establishing management units for pine tree plantations, based on soil surveys performed in lands under investigation located in the western portion of the state of Santa Catarina. Two hypotheses were modeled using the local pine production system, which make...