Abstract:

This study measured genetic variation in growth and wood traits in seven 17-year-old open-pollinated larch hybrid families and three control progeny testing forests and conducted the correlation analysis, comprehensive evaluation and selection. The results showed that there were variations within the families as well as between families. Latewood had greater coefficient of variation than earlywood. There were abundant variations in the volume, tracheid length-width ratio, resin canal proportion and the coefficients of variation were between 26.2%-85.3%. There was small variation in the Holo cellulose (HC), early wood microfibrillar angle (MFA) and tracheid proportion and the coefficients of variation were between 1.4%-8.1%. There were significant differences in HC, early wood and latewood MFA, tracheid length-width ratio, latewood radial diameter, latewood cell wall ratio, latewood tracheid wall thickness-diameter ratio and tracheid proportion between treatments. There were differences in volume, tracheid length, tangential diameter, early wood and latewood number of cells per square millimeter between treatments. The family heritability were between 59.3%-92.7%, suggesting that these traits had potential for pulpwood selection. There was significantly positive correlation between volume and HC, and there were positive correlations between volume and MFA, tangential diameter, late wood tracheid wall thickness-diameter ratio and tracheid proportion, while there was negative correlation between tracheid length-width ratio and late wood number of cells per square millimeter. Correlations were negatively high between basic density and volume, significantly negatively high between basic density and HC, positively high between basic density and tracheid length-width ratio, early wood MFA, latewood number of cells per square millimeter, negatively high between HC and late wood number of cells per square millimeter, significantly negatively high between tracheid length-width ratio and late wood cell wall ratio, and significantly positively high between early wood MFA and tracheid proportion. I₃, I₄, and I₉ were the idealist index. Based on growth and wood traits, 3 families were selected for pulpwood production: Xingan 7 ×Japan 77-2(Larix gmelinii 7×L. kaempferi 77-2), Japan 5×Chang 77-3(Larix kaempferi 5×L. olgensis 77-3) and Japan3×Xingan 9(Larix kaempferi 3×L. gmelinii 9). The family trait genetic gain was: volume (34.7%), late wood cell wall ratio (11.0%), HC (7.5%), tracheid wall thickness-diameter ratio (6.2%), tracheid length-width ratio (4.5%), latewood MFA (3.2%), latewood number of cells per square millimeter (0.3%).

Key words: hybrid larch(Larix), open-pollination, pulpwood, wood traits, genetic variations, family selection