title: Examining the cause of high inbreeding depression: analysis of whole-genome sequence data in 28 selfed progeny of Eucalyptus grandis.
abstract: The genome-wide heterozygosity at 9590 genes, all heterozygous in a single Eucalyptus grandis parent tree, was examined in a group of 28 S1 offspring. Heterozygosity ranged from 52-79%, averaging 65.5%, much higher than the 50% expected under random segregation, supporting the occurrence of strong (47%) selection against homozygosity. The expected pattern of heterozygosity from theoretical calculations and simulations for recessive detrimentals (pseudo-overdominance) and intrinsic heterozygote advantage was examined and compared with that observed. The observed patterns are consistent with at least several detrimental loci with large effects on both parental chromosomes of the 11 pairs. It is likely that 100 or more genes, many with substantial effects on viability, are contributing to this inbreeding depression. Although our genome-wide analysis of nearly 10 000 genes strongly suggested that pseudo-overdominance was responsible for the observed high inbreeding depression, heterozygote advantage could not be excluded. Finding inconvertible evidence of the cause of inbreeding depression still presents a difficult challenge. This study is the first theoretical examination of the genomic effect of inbreeding in a forest tree and provides an approach to analyze these data to determine the extent and cause of inbreeding depression across other plant genomes.
authors.affiliation: School of Life Sciences, Arizona State University, Tempe, AZ, 85287, USA.
authors.forename: Philip W
authors.initials: PW
authors.lastname: Hedrick
authors.affiliation: US Department of Energy Joint Genome Institute, 2800 Mitchell Drive, Walnut Creek, CA, 94598, USA.
authors.forename: Uffe
authors.initials: U
authors.lastname: Hellsten
authors.affiliation: Laboratório de Genética Vegetal, EMBRAPA Recursos Genéticos e Biotecnologia, PqEB, Brasilia, DF, 70770-970, Brasil.|Programa de Ciências Genômicas e Biotecnologia, Universidade Católica de Brasília, SGAN 916, Brasilia, DF, 70790-160, Brasil.
authors.forename: Dario
authors.initials: D
authors.lastname: Grattapaglia
mesh_terms: D032461:Chromosomes, Plant; D003198:Computer Simulation; D005052:Eucalyptus / Q000235:genetics*; D018745:Genome, Plant; D006579:Heterozygote; D000071422:Inbreeding Depression; D008957:Models, Genetic; D054817:Pollination; D020641:Polymorphism, Single Nucleotide; D057945:Self-Fertilization
keywords: Eucalyptus grandis; heterozygosity; heterozygote advantage; linkage disequilibrium; pseudo-overdominance; tree; viability