Inheritance of stylar ribonucleases in cherry progenies, and reassignment of incompatibility alleles to two incompatibility groups

Stylar proteins were extracted from parents and seedlings of six progenies of cherry (Prunus avium), separated using isoelectric focusing, and the gels stained for ribonuclease activity. The zymogram of each plant showed two main ribonuclease bands in the region pI 8.3 to 9.6. Progenies from crosses of parents with one band in common segregated into just two classes, whereas progenies from crosses of parents with no common bands segregated into four classes, the two types of segregation corresponding to those expected from semi-compatible and fully-compatible crosses respectively. This behaviour was consistent either with the ribonuclease locus being tightly linked with the self-incompatibility, S, locus, or else with the S locus coding for the ribonuclease variants. Evidence favouring the latter hypothesis is discussed. An apparently anomalous segregation led us to assign to 'Bradbourne Black' a genotype different from that previously reported, and analysis of some other cultivars in the same incompatibility group, Group VII, led us to conclude the genotype of this group is S3S5, and not S4S5 as previously reported. Correspondingly, we suggest the genotype of Group V is S4S5, and not S3S5. Five new S alleles, S-7, S-8, S-9, S-10 and S-11 were proposed in parental cultivars and selections that had not previously been assigned a genotype.