INVESTIGATIONS ON THE SPORTING PROCESS IN GREENHOUSE CHRYSANTHEMUMS

The chromosome numbers of 56 varieties of greenhouse chrysanthemums were determined. Fifty-one varieties belonged to 10 'families' of sports and the chromosome numbers of the sports were compared with those of their vegetative parents. Sporting, mostly flower colour mutation, was accompanied by the gain or loss of a few chromosomes in about 30 per cent of the cases. Two plants with different chromosome numbers but with the true varietal flower colour were found.The most frequent chromosome number in the authors' material was 2n = 57. The range was 2n = 45–64. Mitotic irregularities and chromosome number variation within individuals were observed. Attempts to induce sporting by hot water treatment failed.Varieties with large inflorescences had higher chromosome numbers (2n = 58–64) than varieties with medium or small inflorescences (2n = 54–58), but in most of the material varieties with small inflorescences differed little in chromosome number from those with medium-sized inflorescences. Five additional varieties with very small inflorescences had lower chromosome numbers (2n = 45–55).