Expression of the Sfa-allele in homozygote genotypes (SfaSfi) indicates a mutation in the stylar part of the Sf haplotype as origin of self-compatibility in almond

Abstract

The Sf allele shows two different expressions: an active form (Sfa) inducing self-incompatibility and an inactive form (Sfi) inducing self-compatibility. Their interaction was studied in several hetero/homozygous genotypes (SfiSfa) in order to establish if self-compatibility was dominant as previously suggested. The seedling genotype was determined by PCR amplification of genomic DNA with universal and specific primers and the phenotype by pollen tube growth. The results showed full self-incompatibility of the SfiSfa genotypes as a result of the recognition of any kind of Sf pollen (Sfi or Sfa) by the style, where Sf-RNase was produced due to the presence of the Sfa allele. These results confirm the allelism of the Sf allele with the series of S alleles of self-incompatibility and that a mutation in the stylar part of the Sfa haplotype has led to the self-compatibility of the Sfi form. The recognition of the Sfi pollen by the Sfa style confirms that the presence of the Sfi haplotype does not ensure self-compatibility, and that in these hetero/homozygous genotypes the expression of Sfa is dominant over that of Sfi