was established in a polyethylene tunnel. Yield and runnering capacity were recorded in two seasons. The cultivars were the English 'Flamenco' and 'Everest',.
Performance of Everbearing Strawberry Cultivars in a Nordic Climate A. Nes and A. Sønsteby Arable Crops Division Norwegian Institute for Agricultural and Environmental Research, Nes Hedmark Norway
O.M. Heide Department of Ecology and Natural Resource Management Norwegian University of Life Sciences, Ås Norway
Keywords: cultivars, everbearing, Fragaria × ananassa, strawberry, yield Abstract In the Nordic strawberry industry only single-cropping cultivars are used. Several everbearing cultivars have been tried, but neither yield nor quality has been satisfactory. In 2005, new everbearing cultivars were collected and an experiment was established in a polyethylene tunnel. Yield and runnering capacity were recorded in two seasons. The cultivars were the English ‘Flamenco’ and ‘Everest’, the Dutch ‘Elan’ and the Norwegian ‘Rita’, ‘Rondo’, ‘Ridder’ and ‘Rosa’. Plug plants were planted in double rows on low ridges mulched with plastic at a plant density equivalent to 50,000 plants per ha. A block design with 20 plants per plot and four replicates was used. The field was harvested two to three times a week during the whole season from June until the beginning of October in both years. Berry size was recorded at all harvests while taste and general performance were evaluated using a scale 1-9. In the first year, the everbearing cultivars had significantly higher yield than the single-cropping cultivars due to more inflorescences, but this was levelled out the second year. While the cropping season of the single-cropping cultivars is only about four weeks, the everbearing cultivars were picked from late June until beginning of October, in both years. The highest yields were obtained by ‘Everest’ (729 and 844 g) followed by ‘Rita’ and ‘Ridder’. The cultivars ‘Elan’ and ‘Rondo’ scored highest both in taste and general performance. ‘Everest’ also performed well, but flavour was not acceptable. INTRODUCTION During the years, many single-cropping and some everbearing cultivars from different breeding programs have been tested in the Nordic climate in Norway (Nes, 1997). While several single-cropping cultivars have been accepted because of good yield of high quality, no everbearing types have been accepted. The strawberry season in Norway begins in mid-June (at about 58°N), and ends about mid-August (at about 63°N). Most of the strawberry production is, however, largely concentrated in the South-Eastern part of the country, giving a short season of only 3-4 weeks in this period, too many berries are over-flooding the marked, and the prices are low. To avoid this there is an increasing interest of alternative production methods to stretch the season. Different strategies have been tried: waiting bed plants or to utilise the effects of different preconditioning treatments in the main cultivar ‘Korona’ (Sønsteby et al., 2006; Nes et al., 2002). Use of everbearing cultivars is another alternative. The paper presents results from an investigation where some new everbearing cultivars have been tried in our climate. MATERIAL AND METHODS The cultivars ‘Flamenco’ and ‘Everest’ from England, the Dutch ‘Elan’ and the Norwegian ‘Rita’, ‘Rondo’, ‘Ridder’ and ‘Rosa’ were collected and an experimental field was established in a polyethylene tunnel at Bioforsk Øst Kise (60°40’N, 10°11’E) in the South-Eastern part of Norway in autumn 2005. Plug plants were planted in double rows on low ridges mulched with plastic at a plant density equivalent to 50,000 plants per ha. A block design with 20 plants per plot and four replicates was used. The experimental field was fitted with a pressure compensated trickle irrigating system with an emitter spacing of 50 cm and a capacity of 1.6 L/h. Fertigation was carried out twice a week during most Proc. VIth Internat. Strawberry Symposium Ed.: J. López-Medina Acta Hort. 842, ISHS 2009
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of the growing season. Predators were used to control pests like spider mite (Tetranychus urticae) and thrips (Thysanoptera spp.). Because of heavy attack of different pests, all plants of the cultivars ‘Rita’ and ‘Rosa’ were removed in week 34 the second year. The plots were harvested two to three times a week during the whole season from June until beginning of October in the years 2006 and 2007. Yield, berry size and discarded berries were recorded at all harvests while taste and general performance were evaluated three times early in the season using a scale 1-9 (not shown). Data of outside temperature are collected from the official meteorological station close to the experimental field (Table 1). RESULTS AND DISCUSSION The observations presented in Table 1 show that the temperatures were very high compared to the 30 year normal (1960-1990) in both years, with an extraordinary warm July and August the first year. Early in the season the temperatures were higher in the second year than the year before. Average temperatures were well above normal during the growing season in both years. Yield
With the exception of ‘Everest’, all cultivars yielded less the second year (Table 2). On average for the seven cultivars the crop was reduced by more than 25% the second year. This is in contradiction to single-cropping cultivars that in a similar experiment (data not shown) gave more than 500% yield the second year. ‘Everest’ had the highest yield both years, followed closely by ‘Rita’ the first year. The latter had, however, only half crop the second year. The yield of ‘Rosa’ was even more reduced the second year. Besides ‘Everest’ the cultivars ‘Elan’, ‘Ridder’ and ‘Rondo’ also had acceptable yield the second year. Berry Size and Grading According to The Norwegian Standard only berries with diameter above 25 mm are saleable on the fresh marked. In this experiment ‘Rita’ had significantly smallest berries and only 30-40% of the total yield could be sold (Table 2). The cultivars ‘Everest’, ‘Flamenco’ and ‘Rondo’ gave biggest berries, but the berry size of ‘Everest’ was significantly reduced the second year. The cultivar ‘Rondo’ had biggest berries in average of both years and 40% of the crop of this cultivar had berries with a diameter above 30 mm. Discarded Berries There were most discarded berries the first year. There is no obvious explanation for that, but some attack of both strawberry mildew (Sphaerotheca macularis) and thrips (Thysanoptera spp.) occurred in the periods with very high temperatures in July and August the first year and this could have had an affect. The fact that the cultivars ‘Rita’ and ‘Rondo’ were removed from the field in week 34 also had an influence. Significant differences in resistance between the seven cultivars are demonstrated. Harvesting Season In the first year the cultivars gave the first ripe berries the last week of June – some already the week before (Fig. 1). In the second year the temperatures in May and June were higher and the season began about one week earlier. Both years the yield showed a peak in the second and third week followed by very little yield the next three to four weeks when yield reached a second peak. In the first year the second peak was earlier than in the second year. The temperatures in July and August were much higher the first year making the time from flower induction to harvest shorter. The cultivar ‘Rita’ showed a little different pattern giving a very high early yield in both years but less late in the season when the berry size was very small. The harvesting season in single-cropping cultivars lasts 3-4 weeks but all cultivars in this experiment were picked for a period of 15-17 weeks. Everbearing strawberry cultivars are long-day plants at intermediate and 782
high temperatures, but day-neutral at low temperatures (Sønsteby and Heide, 2007). Therefore, flowers for the early crop peak must have been induced in the autumn the year before, while the late crop peak came from flowers induced and differentiated in the current year. CONCLUSIONS Only a few of the tested everbearing cultivars will be included in further trials. ‘Everest’ was healthy and high yielding but flavour was not acceptable. The cultivars ‘Elan’ and ‘Rondo’ had an acceptable yield and scored highest both in taste and general performance. But mildew may be a problem in ‘Rondo’. The other cultivars were found not acceptable. Literature Cited Nes, A. 1997. Evaluation of strawberry cultivars in Norway. Acta Hort. 439:275-280. Nes, A., Grimstad, S.O., Opstad, N., Hageberg, B. and Hagelund, R. 2002. Stategies of raising transplants for strawberry production in a prolonged season in a Nordic climate. Acta Hort. 567:281-284. Sønsteby, A., Heide, O.M., Grimsby, I. and Grimsby, S. 2006. Out-of-season strawberry production in Norway: Yield responses of cv. Korona to photoperiod preconditioning treatment. Acta Hort. 708:371-374. Sønsteby, A. and Heide, O.M. 2007. Long-day control of flowering in everbearing strawberries. J. Hort. Sci. Biotech. 82:875-884. Tables Table 1. Outside mean temperature in the growing season of the two experimental years compared to normal at the meteorological station Kise, Hedmark. 2006 2007 Normal
May 9.1 9.7 8.5
June 14.4 15.1 13.6
July 18.5 15.5 15.2
August September October May-October 17.0 13.6 7.3 13.3 15.2 15.7 5.7 12.8 14.0 9.6 5.1 11.0
Table 2. Yield (g/plant), grading (%), berry size (g/berry) and discarded berries (%) of seven everbearing strawberry cultivars in two years. Cultivars Everest Flamenco Ritax Rondo Ridder Rosax Elan X
Yield 2006 729 563 709 547 639 663 635
2007 844 491 337 388 574 149 542
Grading in berry diameter 30 mm 2006 2007 2006 2007 2006 2007 25 26 32 45 43 29 30 29 36 35 35 36 61 75 28 22 11 3 29 27 31 33 40 40 32 33 31 32 37 34 39 45 33 34 28 21 42 34 33 38 25 28
Berry size
Discarded berries 2006 2007 2006 2007 12.0 8.6 3.6 2.4 10.3 10.0 9.0 6.4 6.0 5.0 10.2 1.7 12.0 11.1 8.4 4.9 9.5 10.2 3.8 2.8 8.5 7.2 13.5 8.9 9.1 9.0 4.8 3.1
only 24 out of harvests in 2007.
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Figures
150
2006
-1
Yield (g plant )
125 100 75 50 25
-1
Yield (g plant )
0 150 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 2007 Time (week no.) 125 Everest Flamenco Rita 100 Rondo Ridder Rosa 75 Elan 50 25 0 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 Time (week no.)
Fig. 1. Yield (g/plant/week) of seven everbearing cultivars in two years.
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