Mirjana Sadojevic

Growth and flower bud initiation (FBI) were studied in single-stem plants of four biennial-fruiting cultivars in a controlled environment and under field conditions at 60°40′ N. Shoot growth varied widely among the cultivars but was significantly enhanced by high temperature (20 °C) in all cultivars, whereas photoperiod had a subordinate growth effect. FBI data from bud dissection after 6 weeks of cultivation in the phytotron were used to calculate FBI indices for the various cultivars and environment conditions. The indices also varied much among the cultivars but were enhanced by elevated temperature, being highest in ‘Natchez’ and ‘Sweet Royalla’, while ‘Natchez’ was the only cultivar in which FBI was significantly enhanced by short days. The non-vigorous and erect growing ‘Ouachita’ remained vegetative at both temperatures but flowered in spring after overwintering at 0.5 °C. The field experiment confirmed the superior growth vigor of ‘Loch Ness’ and ‘Sweet Royalla’ as well as the photoperiodic sensitivity of ‘Natchez’. The results also confirmed that floral initiation starts in lateral buds located 10–20 nodes below the apex, and from there it progresses in both acropetal and basipetal direction. We conclude that temperature is at least as important as the photoperiod for the control of FBI in biennial-fruiting blackberries.

Environmental conditions during plant raising determine the yield potential of everbearing strawberries. We studied the effect of three rooting dates in the cultivars ‘Favori’ and ‘Murano’ in a greenhouse with 18 ℃ and 20-h long day and under outdoor conditions in Norway. The highest yield of 1.350 g/plant was obtained in ‘Favori’ plants rooted on 1 August and raised outdoors, being at level with ‘Favori’ plants produced in The Netherlands. High yields were mainly related to fruit size and less to fruit number, and determined by a complex three-factor interaction of rooting date, raising environment, and cultivar. The seasonal pattern of fruit flushes and off periods varied significantly between cultivars and treatments. The large first flush of high yielding ‘Favori’ plants was associated with a long off period, while the small first flush in ‘Murano’ resulted in a more even crop distribution. Earliness of ripening and berry harvest was superior in ‘Favori’, which had a larger share of its crop during the first half-season. We conclude that it is possible by choosing the right rooting date and raising environment to produce plants with the same high quality and yield potential under the cool Nordic conditions as those currently produced in Central Europe.