RESEARCH PAPER |
A new self-compatibility haplotype in the sweet cherry Kronio, S5', attributable to a pollen-part mutation in the SFB gene
kovi
1,3
1East Malling Research, New Road, East Malling, Kent ME19 6BJ, UK
2Dipartimento di Colture Arboree, Università degli Studi di Palermo, Viale delle Scienze 11, 90128 Palermo, Italy
3Imperial College at Wye, Ashford, Kent TN25 5AH, UK
* To whom correspondence should be addressed. E-mail: ken.tobutt{at}emr.ac.uk
Kronio is a Sicilian cultivar of sweet cherry (Prunus avium), nominally with the incompatibility genotype S5S6, that is reported to be naturally self-compatible. In this work the cause of its self-compatibility was investigated. Test selfing confirmed self-compatibility and provided embryos for analysis; PCR with consensus primers designed to amplify S-RNase and SFB alleles showed that the embryos were of two types, S5S5 and S5S6, indicating that S6 pollen failed, but S5 succeeded, perhaps because of a mutation in the pollen or stylar component. Stylar RNase analysis indicated active S-RNases for both S5 and S6. The S-RNase alleles were cloned and sequenced; and sequences encode functional proteins. Cloning and sequencing of SFB alleles showed that S6 was normal but S5 had a premature stop codon upstream of the variable region HVa resulting in a truncated protein. Therefore, the self-compatibility can be attributed to a pollen-part mutation of S5, designated S5', the first reported case of breakdown of self-incompatibility in diploid sweet cherry caused by a natural mutation at the S-locus. The second intron of the S-RNase associated with S5' contained a microsatellite smaller than that associated with S5; primers designed to amplify across this microsatellite effectively distinguished S5 from S5'. Analysis of some other Sicilian cherries with these primers indicated that S5' is also present in the Sicilian cultivar Maiolina a Rappu, and this proved to be self-compatible.
Key words: Natural mutation, pollen-part mutant, Prunus avium, self-compatibility, SFB
Received 21 August 2007; Revised 23 October 2007 Accepted 25 October 2007