α-Pinene concentrations in bark tissue affect intra-specific variation in the susceptibility to vole gnawing of Japanese larch

During observations of a 46-year-old progeny test site planted with Japanese larch ( Larix kaempferi) in Japan’s Hokkaido region, we observed extensive damage caused by feeding of the gray red-backed vole ( Craseomys rufocanus). In this site, progeny derived from 15 parent clones of L. kaempferi was planted with intercrossed hybrid ( Larix gmelinii var. japonica × L. kaempferi), enabling us to assess genetic contributions to intra-specific variation while accounting for spatial effects. Quantitation using LiDAR and 3D point-cloud data revealed that the genetic characters estimated for the vole-gnawed area varied widely among the parent clones, suggesting that vole susceptibility is a genetically-based trait. Moreover, there was a significant positive relationship between the vole-gnawed area and mortality risk over the last 15 years, suggesting that vole susceptibility of clones is important in mature larch trees as well as in young trees. A significant negative correlation between the vole-gnawed area and the concentrations of α-pinene was detected in the secondary phloem of L. kaempferi, but not in its hybrid. Thus, α-pinene would be a candidate repellent, and the susceptibility to vole gnawing could be genetically improved by breeding approaches for L. kaempferi.