自殖家系を用いた雄性不稔遺伝子をヘテロ接合型で保有するヒノキ精英樹の発見

We attempted to select heterozygous plus-trees to study a male sterility gene in the Japanese hinoki cypress (Chamaecyparis obtusa (Sieb. et Zucc.) Endl.), which is one of the primary tree species that cause pollinosis. Hence, we produced self-pollinated families derived from eight plus-trees. We observed pollen dispersal at the age of 8 years and pollen cell at the age of 9 years. Male sterile trees were found in two self-pollinated families of "Tanzawa 6" and "Tanzawa 7," at proportions of 22.2％ and 25.0％, respectively. This indicated that these two clones have a male-sterile gene in heterozygotes. All the confirmed male-sterile individuals had no transition from the pollen mother cell stage to the next stage of pollen development. Two self-pollinated male sterile trees in "Tanzawa 7" exhibited normal seed germination, which indicated that they were not female-sterile. These results suggested that these trees are useful for male sterile breeding in Japanese hinoki cypress. However, the seed germination rate and early growth of self-pollinated individuals were inferior to those of other cross-pollinated individuals. Because of the possibility that selfing could also affect pollen cell development, it is essential to perform additional observation using backcross families.