Detection of quantitative trait loci controlling bud burst and height growth in Quercus robur L.

Abstract

Genetic variation of bud burst and early growth components was estimated in a full-sib family of Quercus robur L. comprising 278 offspring. The full sibs were vegetatively propagated, and phenotypic assessments were made in three field tests. This two-generation pedigree was also used to construct a genetic linkage map (12 linkage groups, 128 markers) and locate quantitative trait loci (QTLs) controlling bud burst and growth components. In each field test, the date of bud burst extended over a period of 20 days from the earliest to the latest clone. Bud burst exhibited higher heritability (0.15-0.51) than growth components (0.04-0.23) and also higher correlations across field tests. Over the three tests there were 32 independent detected QTLs ( P<or=5% at the chromosome level) controlling bud burst, which likely represent at least 12 unique genes or chromosomal regions controlling this trait. QTLs explained from 3% to 11% of the variance of the clonal means. The number of QTLs controlling height growth components was lower and varied between two and four. However the contribution of each QTL to the variance of the clonal mean was higher (from 4% to 19%). These results indicate that the genetic architecture of two important fitness-related traits are quite different. On the one hand, bud burst is controlled by several QTLs with rather low to moderate effects, but contributing to a high genetic (additive) variance. On the other hand, height growth depends on fewer QTLs with moderate to strong effects, resulting in lower heritabilities of the trait.

A linkage disequilibrium perspective on the genetic mosaic of speciation in two hybridizing Mediterranean white oaks

“…LG2 outliers found in this study colocalize with one of the two most important QTLs for bud flush (Saintagne et al, 2004;Scotti-Saintagne et al, 2004a;Derory et al, 2010), which is maintained in several crosses (Gailing et al, 2005). Bud flush in oaks is an adaptive ecological trait that is entirely correlated with flowering time (Duccousso et al, 1996) and has pleiotropic effects on pre-zygotic reproductive isolation via assortative mating (Savolainen et al, 2006).…”

Contrasting relations between diversity of candidate genes and variation of bud burst in natural and segregating populations of European oaks

“…Mapping CGs and detection of QTLs for bud burst Plant material and assessments of bud burst: QTLs for bud burst were detected within the full-sibling family 3P*A4 comprising 278 full siblings (Scotti-Saintagne et al, 2004). Full-sibling seedlings were sown in spring 1995 and raised in a seed bed (field test 1) in the nursery of the INRA Research Station at Pierroton (near Bordeaux France).…”

“…The full siblings were further vegetatively propagated during two successive campaigns in 1997 (6.2 cuttings per full sibling on average) and 1998 (10.6 cuttings per full sibling), and cuttings were installed in two experimental plantations in the fall of 1998 (field test 2) and spring 2000 (field test 3). Details about the two experimental plantations are given in Scotti-Saintagne et al (2004). Both field tests 2 and 3 are located at the INRA Froot Tree Domain located at Bourran (near the city of Agen in the southwest of France).…”

“…The clinal pattern observed along latitude and altitude is therefore the consequence of natural selection mediated by the temperature gradient, which has occurred during the last 15 000 years, and is not imprinted by the earlier differentiation existing among the refugial populations (Kremer et al, 2002) The between-population variation was shown to be associated to the maintenance of important genetic variation within populations (Scotti-Saintagne et al, 2004). Previous quantitative trait locus (QTL) detection analysis suggested that the important genetic variation was likely due to a large number of genes, with rather small-to-moderate effects (Scotti-Saintagne et al, 2004). Technical limitations or reduced pedigree size in forest trees did not permit to implement QTL cloning.…”

“…Molecular imprint of natural selection for bud burst was tested in two different ways: (i) by comparing the differentiation of CG sequences with control neutral markers (for example, microsatellites) and (ii) by comparing the differentiation of CG sequences between geographical and phenological groups of populations. In segregation populations, we refined the QTL position of the timing of bud burst by compiling observations across environments and years, and compared their position with the position of CG on the genetic map following earlier analysis conducted by Scotti-Saintagne et al (2004) and Casasoli et al (2006). Our overall objective was to strengthen the selection of CGs based on their variation in natural and segregation populations.…”