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Licensed Unlicensed Requires Authentication Published by De Gruyter February 24, 2016

Method for accurate fiber length determination from increment cores for large-scale population analyses in Norway spruce

Zhi-Qiang Chen, Konrad Abramowicz, Rafal Raczkowski, Stefana Ganea, Harry X. Wu, Sven-Olof Lundqvist, Tommy Mörling, Sara Sjöstedt de Luna, María Rosario García Gil and Ewa J. Mellerowicz
From the journal Holzforschung


Fiber (tracheid) length is an important trait targeted for genetic and silvicultural improvement. Such studies require large-scale non-destructive sampling, and accurate length determination. The standard procedure for non-destructive sampling is to collect increment cores, singularize their cells by maceration, measure them with optical analyzer and apply various corrections to suppress influence of non-fiber particles and cut fibers, as fibers are cut by the corer. The recently developed expectation-maximization method (EM) not only addresses the problem of non-fibers and cut fibers, but also corrects for the sampling bias. Here, the performance of the EM method has been evaluated by comparing it with length-weighing and squared length-weighing, both implemented in fiber analyzers, and with microscopy data for intact fibers, corrected for sampling bias, as the reference. This was done for 12-mm increment cores from 16 Norway spruce (Picea abies (L.) Karst) trees on fibers from rings 8–11 (counted from pith), representing juvenile wood of interest in breeding programs. The EM-estimates provided mean-fiber-lengths with bias of only +2.7% and low scatter. Length-weighing and length2-weighing gave biases of -7.3% and +9.3%, respectively, and larger scatter. The suggested EM approach constitutes a more accurate non-destructive method for fiber length (FL) determination, expected to be applicable also to other conifers.

Corresponding author: Ewa J. Mellerowicz, Umeå Plant Science Centre, Department Forest Genetics and Plant Physiology, Swedish University of Agricultural Sciences, SE-90183 Umeå, Sweden, Tel: +46 (0)90 786 8367, Fax: +46 (0)90-786 8165, e-mail:

Acknowledgments and funding

We thank Bo Karlsson for collecting the core samples, Jahid Islam for the microscopy fiber length analysis, and the funding agencies: Knut and Alice Wallenberg Foundation, Sweden; Bio4Energy, Sweden; and UPSC Berzelii Centre for Forest Biotechnology, funded by Swedish Research Council (VR) and Swedish Governmental Agency for Innovation Systems (VINNOVA).


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Received: 2015-6-15
Accepted: 2016-1-25
Published Online: 2016-2-24
Published in Print: 2016-9-1

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