An overview of the self-incompatibility (S) genotypes of cultivated sweet cherries

Sweet cherries are self-incompatible and cannot be fertilized by their own pollen. Based on empirical observations, the concept of incompatibility groups has been established for sweet cherries, to which cultivars are assigned that are also incompatible with each other. However, they are fertile when combined with cultivars from other incompatibility groups. The nomenclature of incompatibility groups for sweet cherries was originally proposed by R.L. Knight of the John Innes Institute in England. The reason for this phenomenon is a gametophytic self-incompatibility system, which is genetically controlled by a multi-allelic S-locus. Two closely linked genes located at the S-locus are involved in the incompatibility response. One gene encodes for an S-RNase gene that determines the reaction in the style. The second gene encodes an F-box protein, which determines the reaction in the pollen. There are different S-alleles of these genes (S1, S2, S3, etc.). Incompatibility groups are defined by a specific diploid S-genotype. Since the beginning of the 20th century, systematic studies have been carried out to describe the fertilization relationships between sweet cherry cultivars. Since them, information on the S-genotypes of sweet cherry cultivars has been constantly increasing. This information is very important for cherry growing, breeding and breeding research. Currently the S-genotypes of 1,700 sweet cherry accessions have been assigned to 72 incompatibility groups. An overview of all described S-genotypes and their parentage (if known) was published on the internet for the first time in 2017. An update data set from 2023 is available at https://www.openagrar.de/receive/openagrar_mods_00085931.