Effect of Cold Storage Duration on Runner Production in Strawberry Plants in Winter

We examined the effects of cold storage duration and photoperiod on winter runner production of strawberry cultivars. Eight plants of each cultivar were transferred to a refrigerator (4°C, dark) on different dates, thereby creating six chilling treatments: 1500h, 1000h, 500h, 250h, 100h and 0h. Subsequently, all plants were transferred to a glasshouse and grown from 20 December to 22 March with 10°C night/27°C day temperatures and with natural and 16-h day-length conditions. The emergence dates of leaves, runners, and inflorescences were recorded daily for each plant from 12 January to 22 March 2007. Despite differences in the chilling history, photoperiod, and cultivar, no significant difference was found for the total number of leaves produced. When the plants were grown under natural photoperiods, the percentages of lateral buds producing runners were assessed: more than 80% in plants treated with 1500h, 1000h, and 500h cold storage, but less than 50% in plants treated with 250h, 100h, and 0h cold storage. In contrast, for plants grown under a 16h photoperiod, the percentages of lateral buds producing runners were more than 90% in plants treated with 1500h, 1000h, and 500h cold storage, and more than 60% in plants treated with 250h, 100h, and 0h cold storage. Results show that more effective runner plant production was achieved using cold storage together with long-day treatment.