Propagation and Floral Induction of Transplant for Forcing Long-term Production of Seasonal Flowering Strawberries in Japan

In Japan, over 95% of the acreage is covered with plastic to force June-bearing (seasonal flowering, SF) strawberry cultivars to produce fruit from late fall to early summer. During the late 1960s, a forcing technique was developed that advanced flower bud initiation to late summer and prevented the transplants from becoming dormant during winter. This new forcing technique involved nitrogen starvation of nursery plants to induce floral initiation. Until about 1980, strawberry growers in Japan used runner plants produced in waiting beds, but most transplants are now produced in plastic pots under rain shelters to avoid soil-borne diseases. Recently, the use of tray plants produced from hanging runner cuttings has become popular. To induce early floral initiation, the following artificial low temperature (LT) treatments have been established: (1) “Yarei”, a combination of a short day with solar radiation and LT under darkness in cooling facilities (Yarei-ko); (2) “Kaburei”, continuous dark-LT with refrigeration facilities including industrial warehouses; and (3) “Kanketsu-reizo”, intermittent LT storage. An overview of the technologies applied to plant propagation and the control of floral initiation of Japanese SF cultivars is provided in this review.