PROBLEMS OF BREEDING LATE RIPENING STRAWBERRY CVS. IN POLAND

A basic difficulty in breeding late ripening cultivars in Poland is the lack of a broad base of the initial breeding material that can be used for this purpose. The existing cultivars, which are late ripening in most cases also have disadvantageous traits such as male sterility, poor productivity and crop quality and low resistance to the principle deseases. An additional problem is poor winterhardiness of these varieties.

In the period from 1985 to 1987, breeding investigations were carried out on late ripening cultivars using a very late Russian variety, Kubanska Pózna. This variety was crossed with 14 other cultivars or clones, most of them being late ripening genotypes. The F₁ progeny showed great segregation in respect to the ripening season. In those that ripened the latest, there were hybrids obtained from the crosses where as pollinators the very late cultivars were used. Among these progenies a great number of seedling-hybrids ripened at the same time or even later than Kubanska Pózna. On the average, the progeny of these crosses was also better in respect to fruit quality and fruit crop. For the improvement of fruit quality, the best were those crosses, where as paternal forms, firm fruited cultivars were used. About 50 % of the seedlings had only pistillate flowers.