S-Gene
The S-gene has been suggested to be a super gene complex with several linked genes. It is supposed to have at least six (may he more) closely-linked genes which determine length of style (gene G), surface of stigma (S), pollen incompatibility (I'), stylar incompatibility (I"), pollen size, and/or shape (P), and stamen height (A). Being closely linked they are inherited together but because of crossing over, can be separated. In addition heteromorphic incompatibility can be further characterized by-
- Saprophytically -determined incompatibility reaction,
- Inhibited growth of incompatible pollen tube in the style, and
- Expression of dominance between alleles of the incompatibility genes in both, pollen and style.