Self-incompatibility recognition in Petunia hybrida

Abstract

In Petunia hybrida incorporation of crude or dialysed extract of the stigma and style in the germination medium selectively inhibited germination and tube growth of self-pollen, but did not affect the responses of cross-pollen. The extract from self-compatible buds (3 days before anthesis) was not effective in selective inhibition of self-pollen. Incorporation of extracts from different parts of the pistil showed that self- incompatibility recognition molecules are present in the stigmatic exudate, transmitting tissue of the stigma and 2-3 mm of the subjacent style. Using this in vitro bioassay, the role of lectins and sugars in self-incompatibility recognition was investigated. Incorporation of a lectin in the germination medium (containing pistil extract) as well as the treatment of pollen with a suitable sugar before culture was effective in overcoming selective inhibition of self-pollen. Incorporation of a sugar in the germination medium or treatment of pollen with a lectin before culture had no effect on the selective inhibition of self-pollen. Self-incompatibility in vivo could also be overcome by treating the stigma with a lectin or treating the pollen with a sugar before pollination. These results clearly indicate the involvement of lectin-like components of the pollen and specific sugar moiety of the pistil in self-incompatibility recognition.