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Doctoral thesis, 2002

Genome mapping of quantitative trait loci in Salix with an emphasis on freezing resistance

Tsarouhas, Vasilios

Abstract

The current advancement of biotechnology could provide a better understanding of the genetic control and the molecular basis of quantitative traits in plants. The present thesis focuses on the identification of genes affecting freezing resistance and phenological traits. Two genetic maps were constructed for two interspecific Salix families. The first map was based on a backcross (n = 87) ofthe male clone “Björn” (Salix viminalis x Salix schwerinii) with the female clone “78183” (Salix viminalis) and composed of 325 AFLP and 25 RFLP loci, the latter mainly derived from the Populus genome. The second map consisted of 433 AFLPs and it was based on an F? family (n = 92) with grandparents being a frost susceptible female clone (“Jorunn”; S. viminalis) and a frost resistant male clone (“SW901290”; 5. dasyclados like). The average length ofthe maps and the genome coverage were 2483 cM and 72% respectively, while the average distance between loci was about 11 cM.

Using the genetic map of the backcross family, nineteen quantitative trait loci (QTL) were identified; eleven for growth-related traits and eight for the timing of bud flush. The estimated magnitude of the QTL effect ranged from 12 to 24% of the total phenotypic variance. One QTL for height growth, one for diameter and one for the height:diameter ratio, were found clustered in the same marker interval. One QTL associated with indoor bud flushing coincided with a QTL controlling timing of bud flush in the field. Little evidence was found for QTL stability in height growth over 3 consecutive years.

Ten genomic regions controlling freezing resistance and nine affecting phenological traits were identified during cold acclimation ofthe F? family. The magnitude ofthe phenotypic variation explained by each freezing resistance locus varied over acclimation time (3 - 45%) and there was no time point at which all the QTL could be detected. The single QTL detected for non-acclimated freezing resistance did not reach significance at any time during cold acclimation suggesting an independent relationship between non-acclimated and acclimated freezing resistance in Salix. The determination of QTL position on the map suggested the partial involvement of a common set of genes for autumn freezing resistance and phenology traits. Of the 14 QTL controlling autumn freezing resistance and phenological traits at the indoor experiment, six (43%) were associated with autumn phenology traits i.e. total height increment, dry-to-fresh weight ratio and number of new leaves, as measured in the field. A major locus with multi-trait association in both indoor and outdoor experiments was detected. The presence of genes with large effect for growth and adaptation traits suggests that a marker assisted selection breeding scheme could accelerate the breeding process in Salix.

Keywords

genetic mapping; QTL mapping; genetic markers; freezing resistance; phenology traits; growth traits; Salix

Published in

Acta Universitatis Agriculturae Sueciae. Agraria
2002, number: 327
ISBN: 91-576-6164-2
Publisher: Swedish University of Agricultural Sciences

Authors' information

Tsarouhas, Vasilios
Swedish University of Agricultural Sciences, Department of Plant Biology

UKÄ Subject classification

Genetics and Breeding
Forest Science

URI (permanent link to this page)

https://res.slu.se/id/publ/117503