Breeding strawberry varieties for early forcing in glasshouses by heating and long-day illumination has certain aspects deviating from breeding varieties for the open. Varieties for early forcing must respond quickly on forcing by an adequate vegetative development, and early flowering and fruiting.It is essential that, prior to forcing, the dormancy of the plants is broken by means of adequate chilling.In phytotron experiments three varieties, used for forcing in the Netherlands, Glasa, Gorella and Redgauntlet, were compared with the American varieties Florida 90 and Tioga as to duration of dormancy and to chilling requirement. Judged by the degree of elongation of the plants, Florida 90 and Tioga showed the least chilling requirements. Than followed Glasa while Gorella clearly needed more chilling and Redgauntlet most.The time of flowering was independent of the degree of dormancy and of the growth response of the plants. In breeding for early forcing a short dormant period will have to be combined with early flowering.

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