Verification of Year-round Production of Clean Larch Cuttings Shoots for Using a Closed Nursery

Abstract

When producing F₁ hybrid larch (Clean Larch), cuttings, there is a supply shortage because the number of shoots for cuttings is low, the rooting rate is unstable, and the rooted cutting production rate is low. However, the number of shoot for cuttings increases under artificially controlled conditions and the rooting rate stabilizes. In this study, we developed a closed nursery as a prototype for commercial production and produced cuttings throughout the year. After rooting, the cuttings were transplanted into containers filled with a slow-release fertilizer medium, acclimatized in a greenhouse, and overwintered in the field during the winter. Consequently, the rooting rate did not differ significantly from month to month even after 1 year of continuous cuttings (deviation analysis), and the annual average rooting rate was 81.1％, indicating a stable rooting rate throughout the year. However, growth after transplanting varied depending on the cutting time (analysis of variance), and the percentage of seedlings obtained was low (23％ to 90％), indicating the need for improving low-temperature acclimation methods and fertilizer application. However, the growth rate of rooted cuttings after transplanting is low depending on the timing of cuttings, so it is necessary to promote growth by improving the fertilizer application method.