ON THE GENETICS OF INCOMPATIBILITY IN SWEET CHERRIES .1. IDENTIFICATION OF S-ALLELE IN SELF-INCOMPATIBLE CULTIVARS

In vitro pollen tube growth was studied in numerous cross combinations as well as crosses on the tree with the aim to identify the S allele constitution in sweet cherries. The recently released Jork cultivars ' Erika', 'Valeska', 'Oktavia', and 'Regina' are Incompatible among each other and with the varieties 'Van' and 'Venus', whose S allele consti tution is known to be S1S3. They, thus, belong to the same incompatibi lity group II. The sister cvs 'Johanna', 'Karina', 'Oktavia', 'Regina' , 'Viola' proved to belong to four different S genotypes, thus, demons trating a heterologous combination of the parents 'Schneiders Spate Kn orpel' and 'Rube'. Since two of the cvs are S1S3 each of the parents m ust have contributed one of the alleles. The local cvs from the Lower Elbe District used in cross combinations with 'Rube' obviously are fai rly closely related. Most of them share one S allele. 'Alma', 'Annabel la' and 'Bianca' were identified as being S1S5 like 'Valera'. The Engl ish cultivar 'Mermat' cannot be S1S3 as given by MATTHEWS (1979). It i s fully compatible with 'Van'. A progeny with 'Sunburst', S3S4, segreg ates 1:1 for SF : SI) which points at a heterologous combination. BOS COVIC and TOBUTT (1996) found 'Mermat' to be S1S6. This is in full agr eement with our pollination results. 'Hedelfinger' is fully compatible with 'Burlat' and, thus, cannot be S4S5. It cannot be a 'universal do nor' either because of observed incompatibilities. However, the S alle les of none of these cvs are identified. 'Hedelfinger' cannot belong t o groups I to IV,VI, VII, and IX.