Figure 3.
Relationships between phenotype and genotype in GSI (A) and SSI (B). The pistil (stigma) phenotype presented here is S1S3 codominance, to clearly demonstrate the difference between the GSI and SSI. In both types of SI, pollen is rejected when the SI phenotype of pollen is identical to that of the pistil (stigma). (A) In the case of GSI, the pollen phenotype is identical to the genotype. The pistil phenotype of the GSI is always expressed in codominance. (B) In the case of SSI, the pollen phenotype is determined by interaction of the parental genotype; therefore, there is a dominance relationship at the pollen side. If S1 is dominant over S2, all pollen grains produced from the S1S2 pollen parent show S1 phenotype, and are rejected on the S1S3 (S1 = S3) stigma. In contrast, on the same stigma (S1 = S3), if S3 is recessive to S4 at the pollen side, all pollen grains, which show S4 phenotype, germinate and pollen tube penetration is observed.