Development of aneuploid cultivars of dwarf apples

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In order to develop aneuploid cultivars of dwarf and excellent-quality apples, we grew seedlings from reciprocal crosses between triploid (3x) and diploid (2x) cultivars, leading apple cultivars in Japan, to perform an examination focusing on the tree size, fruiting, and fruit characteristics.1. In both percentages of flowered cross seedlings and fruited ones 10 years after sowing, 2x X 3x was clearly superior to 3x X 2x but inferior to 2x X 2x. For the trunk circumference of seedlings 11 years after sowing, 2x X 2x was the thickest, 2x X 3x was middle-sized and 3x X 2x was the smallest in size.2. Comparative examination was performed on characteristics of matured fruits in 2x X 3x and 2x X 2x seedlings. It is presumed that there is no significant difference in pericarp color between 2x X 3x and 2x X 2x. For fruit sizes, 2x X 3x was found to be classified into cross combination being equivalent to 2x X 2x in size and other combinations of smaller size. Also for fruit firmness, Brix, acidity and soluble solid/acid ratio, 2x X 3x showed differences depending on cross combinations. However, all of these combinations exhibited a soluble solid/acid ratio of 26.3- 47.8%, falling within the range of table apple cultivars. Therefore, it was found that seedlings of 2x X 3x were good as materials for actual breeding.3. Among cross seedlings from 'Fuji' X 'Jonagold' of 2x X 3x, we could find a seedling that had excellent fruit characteristics (4FJ1 as provisory name). For this type of seedling, the tree showed a trend of dwarfness and fruitfulness.The chromosome number in a somatic cell of this seedling could not be confirmed.The greatest feature of cross seedling 4FJ1 is its 'sweet and acid' taste and it is most likely to be a new cultivar.