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Research article2016Peer reviewed

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

Chen, Zhi-Qiang; Abramowicz, Konrad; Raczkowski, Rafal; Ganea, Stefana; Wu, Harry X.; Lundqvist, Sven-Olof; Morling, Tommy; de Luna, Sara Sjostedt; Gil, Maria Rosario Garcia; Mellerowicz, Ewa J.


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.


expectation-maximization; fiber length; increment core; optical fiber analyzer; Picea abies; tracheid length

Published in

2016, Volume: 70, number: 9, pages: 829-838