Mirjana Sadojevic
Avdelingsingeniør
Sammendrag
The chilling requirements of ‘Junifer’, ‘Rovada’ and ‘Red Dutch’ red currants and ‘Mucurines’ and ‘Pax’ gooseberries were studied under controlled environment conditions. Field grown single-stem potted plants were chilled at 0°C from October 15 for 0 to 20 weeks and forced in a lighted greenhouse at 20°C and 18 h photoperiod for 60 days for recording of budbreak and flowering. None of the red currant plants were able to break without chilling, while the number of breaking buds increased linearly with more than four weeks of chilling, and fastest so in ‘Junifer’. ‘Red Dutch’ proved to have a particularly deep and stable dormancy. Comparable but markedly lower chilling requirements were found in the two gooseberry cultivars. While more than 20 weeks of chilling were required for full dormancy release in the red currant cultivars, 16 to 20 weeks were adequate for the ‘Mucurines’ and ‘Pax’ gooseberries, respectively. This compares with a chilling need of 14 weeks at 0°C previously found for most commercial black currant cultivars under the same conditions. The results also confirm that, as previously demonstrated for black currants, flower development requires more chilling than bud break itself also in red currants and gooseberries. This highlights the need for extended chilling of the plants before the plants are set to forcing in modern tunnel production. We also conclude that the red currant cultivar ‘Rovada’ with its large berry trusses seems particularly well suited for tunnel production.
Sammendrag
We studied the environmental control of shoot growth and floral initiation in annual shoot plants of four red currant cultivars under phytotron conditions. Under natural day length conditions at Ås, Norway (69°40’N), the cultivars ‘Junifer’, ‘Red Dutch’, and ‘Rosetta’ ceased growing and initiated irregular flower formation at 24 and 18°C in late August, indicating a critical photoperiod of approximately 15 h. At 12°C and under outdoor conditions, the processes were delayed by 3-6 weeks depending on the cultivar, indicating a critical photoperiod of approximately 14 h under Nordic field conditions. In 10-h short day (SD), the cultivars ‘Junifer’, ‘Red Dutch’ and ‘Rovada’ ceased growing within 2-3 weeks at 18 and 24°C and within 2-4 weeks at 12°C, followed by irregular floral initiation. However, in 20-h long day (LD), flower initiation was generally scarce, and with contrasting temperature responses among the cultivars, flower initiation was advanced by low temperature in ‘Red Dutch’ and by high temperature in ‘Rovada’ and ‘Junifer’. Flowering performance in the following spring confirmed these results, which demonstrate that red currants are quantitative SD plants with diverse temperature and photoperiod interactions.
Sammendrag
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