Genetic architecture of spring and autumn phenology in Salix

Luisa Ghelardini,Ann Christin Rönnberg-Wästljung,Martin Weih,Sofia Berlin,Ulf Lagercrantz,Niclas Gyllenstrand

doi:10.1186/1471-2229-14-31

Abstract

BackgroundIn woody plants from temperate regions, adaptation to the local climate results in annual cycles of growth and dormancy, and optimal regulation of these cycles are critical for growth, long-term survival, and competitive success. In this study we have investigated the genetic background to growth phenology in a Salix pedigree by assessing genetic and phenotypic variation in growth cessation, leaf senescence and bud burst in different years and environments. A previously constructed linkage map using the same pedigree and anchored to the annotated genome of P. trichocarpa was improved in target regions and used for QTL analysis of the traits. The major aims in this study were to map QTLs for phenology traits in Salix, and to identify candidate genes in QTL hot spots through comparative mapping with the closely related Populus trichocarpa.ResultsAll traits varied significantly among genotypes and the broad-sense heritabilities ranged between 0.5 and 0.9, with the highest for leaf senescence. In total across experiment and years, 80 QTLs were detected. For individual traits, the QTLs explained together from 21.5 to 56.5% of the variation. Generally each individual QTL explained a low amount of the variation but three QTLs explained above 15% of the variation with one QTL for leaf senescence explaining 34% of the variation. The majority of the QTLs were recurrently identified across traits, years and environments. Two hotspots were identified on linkage group (LG) II and X where narrow QTLs for all traits co-localized.ConclusionsThis study provides the most detailed analysis of QTL detection for phenology in Salix conducted so far. Several hotspot regions were found where QTLs for different traits and QTLs for the same trait but identified during different years co-localised. Many QTLs co-localised with QTLs found in poplar for similar traits that could indicate common pathways for these traits in Salicaceae. This study is an important first step in identifying QTLs and candidate genes for phenology traits in Salix.

Highlights

In woody plants from temperate regions, adaptation to the local climate results in annual cycles of growth and dormancy, and optimal regulation of these cycles are critical for growth, long-term survival, and competitive success
Adaptation of the annual cycles of growth and dormancy to the local climate is critical for survival and competitive success of woody plants
Such local adaptation has been described in several species, and it can be seen as clines in phenology traits, including the timing of leaf emergence, leaf senescence, and growth cessation [1]

Summary

Introduction

In woody plants from temperate regions, adaptation to the local climate results in annual cycles of growth and dormancy, and optimal regulation of these cycles are critical for growth, long-term survival, and competitive success. Adaptation of the annual cycles of growth and dormancy to the local climate is critical for survival and competitive success of woody plants Such local adaptation has been described in several species, and it can be seen as clines in phenology traits, including the timing of leaf emergence, leaf senescence, and growth cessation [1]. Decreasing photoperiod (day-length) is the main environmental cue inducing growth cessation and bud set in many perennial plants [14], including poplar [15]. This response to photoperiod is under strong genetic control [16,17,18] and is maintained when trees are moved between latitudes [19]. It is not clear to what extent senescence and bud set are under independent genetic control [26,27]

Methods

Results

Discussion

Conclusion