Study of flower bud differentiation and development to improve strawberry productivity

In order to extend out-of-season strawberry production in protected culture it is common to use plants with pre-formed flower buds to increase yield. This study aimed to characterize the flower bud differentiation in different commercial plant types and to examine the dynamic of the flowering throughout fall, winter and spring production in short-day (SD) and day-neutral (DN) strawberry cultivars. Experiments were conducted in two seasons, in 2017/2018 trials were carried out on combinations of three cultivars with three types of high-altitude nursery plant (SD ‘Dream’/tray plant, SD ‘Calinda’/bare root plant and DN ‘Harmony’/mini tray plant) and in 2018/2019 on cold-stored tray plants of four SD cultivars (‘Darselect’, ‘Deluxe’, ‘Donna’ and ‘Dream’). The dynamic of flowering was examined from November until June in the first season and from September until January in the second one. Trials were established in bench-top substrate culture system in high tunnels. Flower bud differentiation in the nursery varied among cultivars/plant types and autumn flower came earlier for ‘Dream’/tray plant. An increase in the number of crowns and the development of preformed flower buds was observed. At the same time a new phase of floral differentiation took place. There was a gradual increase in the number of floral meristems with a higher rate of floral differentiation in ‘Dream’ and ‘Harmony’. For the SD cultivars, floral meristems differentiation decreased at the end of fruit production, while for DN cultivar it continued. ‘Donna’ tray plants presented a higher number of floral meristems than other cultivars. However, this was not reflected in a high autumn and winter yield. With cold stored tray plants, floral differentiation of new buds was verified in the second half of the cycle, with ‘Darselect’ showing a higher number of reproductive structures, making it the most productive. The dynamic of flowering was similar among cultivars.