2006 年に徳島市城山に植樹されたホルトノキの苗木の現状 : 生育状況とホルトノキ萎黄病感染状況について

Elaeocarpus zollingeri (synonym: E. sylvestris) was one of dominant trees in Mt. Shiroyama in the Tokushima City until 1970s, however, most of adult trees have died by Elaeocarpus yellows. To prevent extinction 300 nursery trees were planted at the foot of the mountain by local volunteers in 2006. In this study we investigated their survival, growth, and infection status of the disease. We found 40 nursery trees have survived (survival rate was 13%). Survived trees were abundant in areas facing the south, and most trees disappeared in areas facing the north and the west. Growth of the trees was well also in areas facing the south. Among the survived 40 nursery trees, we found three trees infected with phytoplasma, the pathogen of Elaeocarpus yellows, based on PCR analysis. It is not clear when they were infected with phytoplasma, whether they have infected after the plantation or they already had phytoplasma in the seed. Anyway, the fact that only a few tree is infected must be gratifying in considering the conservation E. zollinger in Mt. Shiroyama.