A PISTIL-MUTATED S-ALLELE CONFERRING SELF-FERTILITY IN EUROPEAN PEAR

European pear exhibits a gametophytic self-incompatibility system controlled by the polymorphic S-locus.
The present study was aimed on investigation of self-fertility in two European pear cultivars, ‘Abugo’ and ‘Ceremeño’, using fruit/seed setting and pollen tube growth examination.
S-genotyping through S-PCR and sequencing identified a new S-RNase allele in the two cultivars, with identical deduced amino acid sequence as the functional S₁₂₁ RNase but differing at the nucleotide level.
The analysis of crosses, between cultivars bearing the wild type and the new S-RNase allele, and test-pollinations, suggested that the new allele is a pistil-mutated variant of S₁₂₁ conferring self-compatibility (S₁₂₁^°). Moreover, reciprocal crosses between cultivars with S₁₂₁ and S₁₂₁^° further highlighted that both S-alleles exhibit the same pollen function; however, only the cultivars bearing S₁₂₁^° had impaired pistil-S function as they failed to reject either S₁₂₁ or S₁₂₁^° pollen.
Moreover RT-PCR analysis showed absence of S₁₂₁^°-RNase gene expression in styles of ‘Abugo’ and ‘Ceremeño’, suggesting a possible explanation for S₁₂₁^° pistil-dysfunction.

I Workshop on Floral Biology and S-Incompatibility in Fruit Species

J. Sanzol

European pear, Pyrus, self-compatibility, S-allele, retrotransposon

https://doi.org/10.17660/ActaHortic.2012.967.8