Results of preliminary selection for the second generation plus trees by private foresters in three genetic tests with controlled pollinated progenies of sugi (Cryptomeria japonica) in Kyushu

摘要

Second-generation plus tree selections were assessed in three genetic tests of sugi (Cryptomeria japonica) in Kyushu: at Kumamoto, Saga, and Miyazaki. The selections were made by private foresters choosing good trees according to their own preferences when the tests were around 30 years of age. A retrospective selection index applied to the results of selection revealed that the foresters had put more emphasis on stem straightness than on growth. This trend was particularly evident at Kumamoto, whereas the foresters at Miyazaki and Saga had allocated nearly the same weight to growth as to stem straightness. Broad-sense heritabilities on dbh, stem straightness and bottom stem crookedness were 0.226, 0.256, and 0.206, respectively. These estimates were regarded as almost the same as narrow-sense heritabilities, because non-additive genetic variances were found to be small. Relative gains, assuming that the selections are propagated with rooted cuttings, were predicted to be around 10% for stem straightness, 7% for bottom-stem crookedness, while the gains on dbh were variable among the tests: ranging from 3% at Kumamoto up to around 8% at Saga and Miyazaki.