Cytological Studies in the Genus Fragaria (Rosaceae)

I. Chromosome association and fertility in induced autotetraploids

抄録

A number of autotetraploids were produced experimentally with colchicine and the frequency of multivalent vs bivalent associations was studied in seven autotetraploid plants of F. vesca. There were interplant variation in the frequency of quadrivalents between the seven autotetraploids of F. vesca and a highly significant correlation between quadrivalent frequency and chiasma frequency. The higher frequency of quadrivalents in 4x F. nippinoca was associated with a higher chiasma frequency.
The pollen fertility of the autotetraploids were not correlated with meiotic irregularities, and the variation in fertility is attributed to genetical factors.
Autotetraploid F. nipponica was partially self-compatible while the corresponding diploid species was completely self-incompatible. This breakdown of the selfincompatible system in the autotetraploid due to interaction of self-incompatible alleles in the diploid pollen is in agreement with the suggestion that the incompatibility genes in Fragaria species act in the pollen gametophyte.