Biotechnological research in Cryptomeria japonica

Abstract

Cryptomeria japonica (common name is sugi or Japanese cedar) is the most important forest tree species in Japan, and its wood is used for house construction, wooden ships, wooden barrels, and many articles for daily use. Artificial plantation of this species is thought to begin more than 500 years ago, and sugi currently covers 44% of Japanese artificial forest. Though discarded wood in forest by thinning or after harvesting is a valuable biomass, most of the discarded wood is left at forest, not used for materials of biomass energy. A traditional breeding program for sugi was started in the 1950s, and ca. 3600 plus trees (healthy individuals with superior growth performance) had been selected mainly in artificial forests. A current problem due to sugi is allergic reactions to pollen (pollinosis). A nationwide epidemiological survey showed that 26.5% of the Japanese population suffers from pollinosis due to sugi pollen. To address this problem, individuals with low male flower setting have been selected from plus trees. Male-sterile mutants were also discovered, and artificial crosses between the mutants and plus trees have been attempted. This review summarizes sugi breeding, concentrating on biotechnological research (DNA marker and genetic transformation). Genetic improvement in artificial forests increases their forest economic value, leading to sustainable forest management. Sustainably managed forests accumulate continuously renewable carbon in their trees, contributing to mitigation of global warming.