For a given plant species, how many types of S-loci exists to prevent self-pollination? I would like to know how often a plant stops fertilization process by other plants, thinking the pollens belong to itself due to limitations of SSI/GSI.

  • $\begingroup$ The answer is going to vary dramatically depending on the species. Have you checked wikipedia? $\endgroup$
    – tyersome
    Commented Jun 22, 2019 at 21:44
  • $\begingroup$ An examples suffices. $\endgroup$
    – Miladiouss
    Commented Jun 23, 2019 at 0:44
  • $\begingroup$ I think you mean to ask how many self-incompatibility alleles generally segregate in natural populations? (@tyersome gives a reasonable answer). I cannot tell if you instead mean how many different S-locus systems (mechanisms) exist. I am happy to provide an alternative answer if you clarify. $\endgroup$ Commented Sep 30, 2023 at 22:20

1 Answer 1


Herrera, Sara et al. 2018 suggest that there are at least 33 S-alleles in apricot.

I believe some species of Brassica have at least 60 S-alleles identified.

However, there are dominance relationships among these alleles, so I don't think you can directly extrapolate from the number alleles to to the rate at which non-self pollen will be excluded. The frequencies of the different alleles within a population will clearly also affect this calculation.

In addition, different individuals with the same S-alleles are more likely to be closely related, so I would hesitate to classify this as a limitation of the system.

Ref: Herrera, Sara et al. “Identification of Self-Incompatibility Alleles by Specific PCR Analysis and S-RNase Sequencing in Apricot.” International journal of molecular sciences vol. 19,11 3612. 15 Nov. 2018, doi:10.3390/ijms19113612


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