Title : Evaluation of incompatibility at germplasm of late sweet cherry cultivars at molecular level
Sweet cherries Prunus avium from Rosaceae family are non-climacteric stone fruit, mainly grown in colder temperate climate countries. Lower temperatures (usually below 8 °C) are necessary to provide chilling requirement for induction of flowers. Sweet cherries belong to a commercially important vegetatively propagated fruit tree species. Late ripening sweet cherry cultivars have a higher commercial importance than sweet cherries ripening early in the season due to bigger fruits and higher quality. From the point of view of human diet, sweet cherry provides a delicious fruit, which is rich in sugars and minerals. It has more calorific value than apple. Sweet cherries are also a significant source of polyphenols with antiradical activity. There is a long tradition of sweet cherry breeding in the Czech Republic in Research and Breeding Institute of Pomology Holovousy Ltd.. Sweet cherry is an out-breeding, self-incompatible diploid species in the Rosaceae family with a genome of 2n =16. Their self-incompatibility is determined by a gametophytic self-incompatibility system (GSI), controlled by a multi-allelic S-locus. It is important to select suitable pollen donors for successful fruit production in plantations with different cultivars. Today, it is possible to detect individual alleles of S-locus by PCR molecular markers. In analysis of late sweet cherry varieties, we detected 10 different S-alleles in total 18 combinations of S-locus, belonging to 17 incompatibility groups. S3, S1 and S4 were the most frequent alleles and III (S3S4) and II (S1S3) were the most frequent incompatibility groups. A suitable pollinator must overlap with its flowering with the pollinated variety and should have also a high flower set. Results are useful for the selection of pollen donors for ensuring of sufficient yields in commercial sweet cherry plantations. The study of phenotypic characteristics and further molecular DNA analyses (SSR markers) were carried out simultaneously to describe the genetic variability of cherry collections. It is also crucial for the further improvement of sweet cherry breeding programs. Cherry breeding programs face a significant challenge to develop cultivars incorporating the range of attributes (including pollinizing conditions) preferred by the various components of production chain.