Reforestation or Genetic Disturbance: A Case Study of Pinus thunbergii in the Iki-no-Matsubara Coastal Forest (Japan)

Abstract

In the twentieth century, a substantial decline in Pinus thunbergii populations in Japan occurred due to the outbreak of pine wood nematode (PWN), Burshaphelencus xylophilus. A PWN-P. thunbergii resistant trees-breeding project was developed in the 1980s to provide reforestation materials to minimalize the pest damage within the population. Since climate change can also contribute to PWN outbreaks, an intensive reforestation plan instated without much consideration can impact on the genetic diversity of P. thunbergii populations. The usage and deployment of PWN-P. thunbergii resistant trees to a given site without genetic management can lead to a genetic disturbance. The Iki-no-Matsubara population was used as a model to design an approach for the deployment management. This research aimed to preserve local genetic diversity, genetic structure, and relatedness by developing a method for deploying Kyushu PWN-P. thunbergii resistant trees as reforestation-material plants into Iki-no-Matsubara. The local genotypes of the Iki-no-Matsubara population and the Kyushu PWN-P. thunbergii resistant trees were analyzed using six microsatellite markers. Genotype origins, relatedness, diversity, and structure of both were investigated and compared with the genetic results previously obtained for old populations of P. thunbergii throughout Japan. A sufficient number of Kyushu PWN-P. thunbergii resistant trees, as mother trees, within seed orchards and sufficient status number of the seedlings to deploy are needed when deploying the Kyushu PWN-P. thunbergii resistant trees as reforestation material planting into Iki-no-Matsubara population. This approach not only be used to preserve Iki-no-Matsubara population (genetic diversity, genetic structure, relatedness, and resilience of the forests) but can also be applied to minimize PWN damage. These results provide a baseline for further seed sourcing as well as develop genetic management strategies within P. thunbergii populations, including Kyushu PWN-P. thunbergii resistant trees.

Biogeography: A Case in Spatial Distribution Pattern of 21 Pinus thunbergii Populations in Japan

“…What's remarkable is that the genetic patterns of these populations may have persisted over time, even after being introduced from a different cluster. These results strongly support the idea that these individuals were introduced by human activity [7]. Additionally, the genetic structure of EST-SSR markers (Figure 2) revealed a distinct pattern and the presence of a geographic cline.…”

“…As documented in history, cultivation and domestication of the species have been taking place for centuries [15]. The human involvement has likely influenced the genetic patterns of P. thunbergii populations across Japan [7].In this study, these historical records correspond with the genetic structure findings from EST-SSR markers, especially along the Japan Sea side. The clustering of populations based on EST-SSR markers strongly suggests that human activities have significantly influenced the spread and genetic structure of the species in Japan.…”

Genetics and Improvement of Forest Trees

“…They also provide useful information for determining the genetic consequences of tree improvement. Mukasyaf et al [6] revealed the population genetic effects of adding Pinus thunbergii Parl. seedlings from pine wood nematode-resistant stock to existing forests.…”