Abstract
Japanese cedar (Cryptomeria japonica D. Don) pollinosis has become a serious allergic disease. Therefore, an important issue is to reduce the amount of airborne pollen by breeding method. There was a great difference in male flower setting among plus tree clones. From the investigation in clonal test plantations, 135 clones were selected with few male flowers. The heritability of male flower setting was high at 0.34. Cry j 1 content of 420 plus tree clones showed variation from 0.38 to 10.23 pg per pollen grain and the heritability of Cry j 1 estimated by parent-offspring regression was very high at 1.0. From these results, it was suggested that a large number of seedling with low allergens could be created by crossing the clones selected low pollen allergen. Male sterility of C. japonica is controlled by a recessive allele at a single locus and is expressed only in homozygotes (aa). We selected that 4 plus tree clones that are heterozygous for a male-sterility gene. It is possible to create superior male-sterile trees by crossing with plus trees possessing the male-sterility gene. The use of these pollinosis preventive cultivars would reduce C. japonica pollen production while maintaining the yield of high quality timber.
