Inheritance of male flower production in Cryptomeria japonica (sugi) estimated from analysis of a diallel mating test

Clonal variation of flower production has been investigated thoroughly in coniferous tree species because of the importance of flowering in seed production from seed orchards. However, the inheritance of flower production by progeny test has not been previously studied well, so the heritability of male flower production of Cryptomeria japonica, the most important species for forestry and the main cause of pollinosis in Japan, was estimated to provide fundamental data for pollen control in seed orchards and plantation forests. Male flower production in C. japonica was investigated for three years using 20 full-sib families created by a diallel mating design with six parents using gibberellin treatment to promote flowering. The narrow-sense individual tree heritability of male flower production in each year was estimated as ranging from 0.777 +/- 0.339 to 1.050 +/- 0.346 by sib analyses. The contribution of general combining ability to the total variance varied from 24.1 to 35.6 %. The highest contribution of specific combining ability was 1.42 %. By selecting the top 50 % of parental clones for reduced male flower production, the genetic gain in lowering male flower productivity was predicted as 46.1-53.0 %. Our results suggest that male flower production in C. japonica is under strong genetic control and that control of male flowering by breeding is possible with a well-designed program.