Question

What are the two types of genetic SI(self-incompatibility) in plants?

Answer 1

Self-incompatibility: incompatibility between the pollen and the stigmas of the same plant- is an intraspecific incompatibility. Self incompatibility blocks fertilization between the two genetically similar gametes, increasing the probability of new gene combinations by promoting outcrossing. This response is genetically controlled by a single genetic locus (S) with multiple alleles. There are two types of self-incompatibility: sporophytic self incompatibility (SSI) and gametophytic self incompatibility (GSI).

GSI occurs when the S allele of the pollen grain matches either of the S alleles of the stigma. In this case, the pollen tube begins developing, but stops before reaching the microphyle.

SSI occurs when one of the two S alleles of the pollen-producing sporophyte matches the S alleles of the stigma. In SSI, the male determinant is expressed in the diploid cells of the anther tapetum and their products added to the pollen as a constituent of the pollen coating. In Brassica, the male and the female determinants of SSI have been determined as a peptide ligand and its cognate receptor, respectively.