Browsing by Subject "marjatuotanto"

The strawberry is the most widely cultivated berry in Finland. Producers in Finland grow short-day varieties of strawberry with the mid-season variety Polka being the most popular. Very little breeding is done in Finland and the characteristics of foreign varieties are not tailored to the local growing con-ditions here. Given these circumstances, it is a challenge to choose varieties for production that will flourish in Finland. The calculated and polyvalent use of different strawberry varieties could prolong the growing season and help stimulate productivity and growth in this area of horticulture. The aim of this research is to develop a rapid test for identifying strawberry varieties whose flowering phenology will suit production in Finland. In this research we aimed to develop a test based on short-day treatment to compare the earliness of different varieties. The influence of short-day treatment on flowering and growth was studied in seven short-day strawberry varieties in a greenhouse experiment. Beside the influence of the treatment on the timing of flowering we tested the relationship between earliness and changes in the vegetative growth of our varieties. The experimental conditions comprised two day-length treatments and one control. The first short-day-treatment lasted six weeks with a photoperiod of 12 h. The second short-day treatment, a so called “step” treatment, lasted nine weeks. The day-length in the step treatment was shortened every three weeks, starting at 16 h, and then dropping to 14 h and 12 h. In the long-day control the day-length was 18 h. The greenhouse temperature was a constant 18 ºC in all treatments. We tested early varieties Honeoye, Elianny, Flair and Wendy, the mid-season variety Polka and late varieties Bounty and Florence. The plants in our experiment didn’t develop as we expected. The early variety Wendy was amongst the first to flower, and the late variety Florence amongst the last in both treatments. The earliness of the other varieties we tested was not consistent with how these varieties flower in the open field. Furthermore, the relative vegetative growth couldn’t be associated with the flowering time. In both short-day treatments the growth of the runners stopped first in the early varieties Wendy, Honeoye and Flair. In the remaining varieties, the growth of the runners was unrelated to the expected earliness of the flowering. The length of the petiole was responsive to the first short-day treatment, but growth of the runners and the petioles did not correlate with early flowering. However slow growth of the late variety, Florence, suggests that the growth rate may be connected with the flower phenology in the variety. Finally, Polka was the variety to exhibit most crown branching in this experiment. According to the results of this experiment the earliness of short-day strawberry varieties cannot be determined with just an experimental short-day treatment. The other growing conditions in the green-house are also likely to affect the response of the tested varieties, potentially masking or interacting with the day-length effect. In addition to day-length, the response of the varieties to the temperature, and to the combined effect of day-length and temperature, should be taken into account. A suitable greenhouse test could comprise day-length and temperature treatments or the combination of both of them. Alternatively flower induction could be performed in the field and subsequently plants could be forced in the greenhouse.