Expression of the S receptor kinase in self-compatible Brassica napus cv. Westar leads to the allele-specific rejection of self-incompatible Brassicanapus pollen

Expression of an S receptor kinase (SRK910) transgene in self-compatible Br assica napus cr. Westar conferred on the transgenic pistil the ability to r eject pollen from the self-incompatible Brassica napus W1 line, which carri es the S-910 allele. In one of the SRK transgenic lines, 1C, virtually no s eeds were produced when the transgenic pistils were pollinated with W1 poll en (Mean number of seeds per pod = 1.22). This response was specific to the W1 pollen since pollen from a different self-incompatible Brassica napus l ine (T2) and self-pollinations were fully compatible. Westar plants express ing an S locus glycoprotein transgene (SLG(910)) did not show any self-inco mpatibility response towards W1 pollen. Transgenic Westar plants resulting from crosses between the 1C SRK transgenic line and three SLG(910) transgen ic lines were also tested for rejection of W1 pollen. The additional expres sion of the SLG(910) transgene in the SRK910 transgenic plants did not caus e any significant further reduction in seed production (Mean seeds/pod = 1. 04) or have any detectable effects the number of pollen grains that adhered to the pistil. Thus, while the allele-specific SLG gene was previously rep orted to have an enhancing effect on the self-incompatibility response, no evidence for such a role was found in this study.