Self-incompatibility leads to disassortative mating in Brassica
Disassortative mating caused by the self-incompatibility locus (S) of the flowering plant genus Brassica. (a) A self-pollinated S1/S2 stigma shows no pollen-tube growth. (b) There is pollen-tube growth for an S1/S2 stigma cross-pollinated with pollen from an S3/S4 heterozygote.
[June Bowman Nasrallah.]