Inbreeding depression and hybrid superiority in growth and wood traits of eucalypt pulp wood

With F1 of self-pollinated Eucalyptus urophylla, F1 of inter-tree-pollinated E. urophylla, F1 of open-pollinated E. urophylla and F1 of E. urophylla * grandis as materials, inbreeding depression and hybrid superiority in growth and wood traits are analyzed and discussed. The results are as follows. ①There was a regularity for E. urophylla that F1 of self-pollinated was subjected to more intense depression than F1 of open-pollinated, and growth traits showed more significant depression than wood traits. ②As to F1 of self-pollinated E. urophylla, height, DBH and volume showed significant or extremely significant depression, while water content of green wood wood density and bark thickness showed no significant depression. ③As to F1 of open-pollinated E. urophylla, height, DBH and volume showed depression to a certain degree, but not significant; here again, water content of green wood, wood density and bark thickness showed no significant depression. ④F1 of E. urophylla * grandis showed significant hybrid superiority in height, DBH and volume, but the hybrid superiority percentage of different cross pairs varied greatly; it showed no hybrid superiority in water content of green wood, wood density and fiber length; its bark thickness and content of 1% NaOh extractives decreased evidently.