Production rate of runner plants in a plant factory with artificial lighting as affected by crown diameter of strawberry propagules

Use of the appropriate propagule size can maximize the propagation rate of strawberry (Fragaria × ananassa) transplants in an autotrophic transplant production method, a novel propagation method in a plant factory with artificial lighting for transplant production. During 90 days after planting the initial propagules, the cumulative number of transplants produced from propagules with a 5 mm crown diameter (CD5) was greater than those produced from propagules with a 4 mm crown diameter (CD4) or a 6 mm crown diameter (CD6). Timescales of propagation cycles (required timescale to produce new propagules; the sum of the time from planting propagules to the emergence of runners and the time from the emergence of runners to the separation of runner plants) of first, second, and third runner plants in CD5 were 2.1 – 20.7% shorter than those in CD4 or CD6. In second and third runner plants, the time from planting propagules to emergence of runners increased as propagule crown diameter decreased; however, the time from emergence of runners to separation of a runner plant decreased as crown diameter decreased. The fluctuation of the timescales of propagation cycles with propagation generation in CD5 was smaller than those in CD4 and CD6. After separating runner plants from their propagules, the number of leaves in CD5 fluctuated less than those in CD4 and CD6. These results indicate that propagules having a 5 mm crown diameter and two leaves are appropriate for the autotrophic transplant production method of strawberry in a plant factory.