PROGRESS IN BREEDING DECAPLOID FRAGARIA × VESCANA
Fragaria x ananassa has existed for nearly 300 years and has been improved through breeding. In contrast, Fragaria × vescana is a very young species with little breeding work done. Among those who have succeeded in producing fertile 10x hybrids between F. × ananassa and F. vesca, D.H. Scott and R. Bauer should be mentioned (Scott, 1951; Bauer, 1959; 1960). Three steps were necessary for the development of fertile decaploid F2 hybrids:
- Tetraploidisation of 2x F. vesca by means of colchicine;
- By crossing 8x F. × ananassa cultivars with 4x F. vesca, hexaploid seedlings were obtained, some of which were slightly fertile;
- Backcrossing of 6x hybrids with F. × nanassa cultivars gave seedlings with different chromosome numbers. Only a small percentage of fertile decaploids were obtained, originating from unreduced gametes of the hexaploid uniting with four gametes of F. × ananassa. Bauer named these hybrids Fragaria × vescana, which combine two F. vesca gametes with eight of F × ananassa (Bauer and Weber, 1989).