self-incompatibility


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self-incompatibility

a condition in plants where certain types of pollen will not form pollen tubes when deposited on the female stigma, thus preventing fertilization. Self-incompatibility prevents self-fertilization and promotes heterozygosity (the mixing of allelic forms). The system is controlled by an S locus with many alleles (see MULTIPLE ALLELISM), and pollen with the same allele as in the stigma will not germinate to form a pollen tube. This is shown in Fig. 279. Self-incompatibility mechanisms are much used to produce HYBRID plants (e.g. various Brassica crops). See also COMPATIBILITY.