Identification of <i>Thujopsis dolabrata</i> var. <i>hondae</i> clones and their distribution across plantations in Ishikawa prefecture

<p><i>Thujopsis dolabrata</i> var. <i>hondae</i>, known as “ate”, is the prefectural tree of Ishikawa. The species has been planted in the form of rooted cuttings or saplings created by layering since at least the 1800s. Such historical planting has led to the development of more than 20 vegetatively propagated local cultivars, but these cultivars have not been classified precisely. Understanding the clones that constitute each cultivar and the genetic relationships between clones is essential when undertaking genetic management of plantations and planning future breeding. In this study, we identified clones of cultivars used for <i>T. dolabrata</i> var. <i>hondae</i> plantations in Ishikawa Prefecture using 12 microsatellite markers, and examined the genetic relationships between clones and the distribution of clones across plantations. We analyzed 224 individuals from three local cultivars, ma-ate, kusa-ate and eso-ate, to act as a reference to identify the cultivars from which the clones in plantations originated, and 180 individuals from 35 plantations. The 180 individuals from plantations were separated into 14 clones, of which 6 accounted for 93.3% of the sampled individuals. The ma-ate cultivar used in plantations consisted of multiple, genetically related clones. In contrast, the clones of the kusa-ate and eso-ate cultivars in plantations were almost fixed. In the southern part of the prefecture, there were only two clones, whereas in the northern part, all 14 clones were present; this reflects the facts that clonal forestry involving this species has developed in the northern area and that a few clones have been selected and spread into the southern area.</p>