Challenge to low-cost reforestation by utilizing callused (unrooted) sugi cuttings

2018 Fiscal Year Final Research Report

• Project/Area Number: 16K14945
• Research Category: Grant-in-Aid for Challenging Exploratory Research
• Allocation Type: Multi-year Fund
• Research Field: Forest science
• Research Institution: University of Miyazaki
• Principal Investigator: Ito Satoshi 宮崎大学, 農学部, 教授 (00231150)
• Co-Investigator(Kenkyū-buntansha): 雉子谷 佳男 宮崎大学, 農学部, 教授 (10295199) ; 平田 令子 宮崎大学, 農学部, 講師 (50755890)
• Project Period (FY): 2016-04-01 – 2019-03-31
• Keywords: 低コスト再造林 / コンテナ苗 / 挿し木 / 植物ホルモン / 根量 / 水耕・ミスト栽培

Outline of Final Research Achievements

We examined usefulness of callused (unrooted) sugi cuttings for low-cost reforestation. We found a possibility that callus has a role of precursor rather than primordia of rooting by generating cytokinin and gibberellin. For establishment of callused cuttings after outplanting, we found that 1) reaching 1.345g of root mass 3 months after summer outplanting is the minimum requirement for survival of cuttings, 2) the initial root mass of 0.1g is the threshold for the survival of cuttings after spring outplanting, 3) defoliation (reducing branch mass to being less than 0.65g) is effective to raise the survival of callused cuttings that have roots more than 0.1g, and 4) paper pots as an alternative to multi-cavity containers would be useful for utilizing cuttings with undeveloped roots. Further, analyses based on irrigation experiments suggested that the cumulative soil water content calculated for preceding 3 weeks is a good indicator explaining the survival of outplanted cuttings.

Free Research Field

造林学

Academic Significance and Societal Importance of the Research Achievements

学術的意義：スギ挿し木の発根メカニズムとして、これまで未解明であったカルスの役割について、カルスが必ずしも根の原基ではないことを確認するとともに、発根の前駆的な役割を持つ可能性が高いことを、内生植物ホルモンの定量によって明らかにすることができた。これにより、挿し木の発根メカニズムのさらなる解明や発根制御技術の発展に寄与できる。
社会的意義：カルス苗に代表される少根苗の植栽後の活着条件を明らかにし、活着率を高める摘葉やペーパーポット活用の可能性を示すことができた。この成果は今後の効率的かつ安価な苗木生産技術の確立を通して、苗の安定供給や確実な再造林に寄与することが期待される。