Vaccinium macrocarpon Ait. –the cranberry of the Ericaceae family is cultivated mostly on high peat bogs. In Poland exist a good climatical conditions and considerable acreage of acid soils for cranberry growing. Cranberries can be consumed solely after processing, mostly as juice and sauce. Cranberries are beneficial for the human organism because they are a good source of vitamin A, B₁, B₂ , B₆ and C, flavonoides, organic acids and other substances. Experiments on investigation of 6 cultivars of the American large fruited cranberries were begun in 2004 at the research plantation of Department of Genetics and Horticultural Plant Breeding in Felin, near Lublin. Seedlings were planted out at spacings of 50×50 cm in specialy prepared beds filled with sphagnum peat. During the experiments the following indices were evaluated: growth rhythm, length of horizontal shoots, number of vertical shoots per 1 m², number of flowers and berries per 1 m² in 4 – fold replications, weight of 100 berries and vitality of pollen. Over two years cultivars ‘Pilgrim’ and ‘Cropper’ had the highest yield (average 662 g and 611 g per 1 m², respectively). ‘Stankavich’ had the lowest yields of all 6 cultivars (average 95.5 g). ‘Pilgrim’ and ‘Cropper’ had the largest fruit size (average 1.55 g and 1.51 g, respectively), ‘Stankavich’ the smallest (av. 0.57 g), and ‘Le Munion’, Nr 20 and ‘Stevens’ were intermediate in fruit size. Interaction clone × year proved to be important in the case of such characteristics as: annual increment of shoots, number of flowers per 1 m², number of berries per 1 m² and weight of berries. The number of grains with alieve cytoplasm was the greatest in ‘Cropper’ and ‘Pilgrim’ cultivars.

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