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Incompatibility in European hazelnut (Corylus avellana L.) is sporophytic and under the control of a single locus on linkage group 5 between markers G05-510 and AU02-1350. In this study, two rounds of marker development and a population of 192 seedlings with known S-alleles that showed recombination between the flanking markers were used for fine mapping. Using the sequences of random amplified polymorphic DNA and simple sequence repeat (SSR) markers and bacterial artificial chromosome end sequences, 36 contigs from the genome sequence of “Jefferson” hazelnut were identified for pursuit. Di-nucleotide SSR markers in those contigs were developed, characterized, and mapped. This reduced the size to a region of 500 kb that contained the S-locus and 50 predicted genes, in which single-nucleotide polymorphism and additional SSR markers were developed. When the new markers were used in fine mapping, they fully exploited all recombination in the fine mapping population and reduced the region to 193.5 kb containing 18 genes. This 193.5-kb region most likely contains the S1 haplotype. A second region, 2 Mbp away from the first in the “Jefferson” genome (V3), is predicted to represent the S3 haplotype based on SSR marker allele sizes and the ratio of parental reads that align to them. Although they appear side-by-side in the “Jefferson” genome (V3), the mapped markers appear in both sequences in the same order. Gene annotations in the S1 and S3 haplotypes are highly similar and include five probable leucine-rich repeat receptor-like protein kinases with homology to Arabidopsis thaliana genes At1g35710 and three probable receptor-like serine/threonine protein kinases with homology to At5g15080 (PIX7). [ABSTRACT FROM AUTHOR]

Self-compatibility is a major breeding objective in sweet cherry. The identification and characterization of new sources of self-compatibility will be useful for breeding and research purposes. In this work, self-compatibility of four local Spanish sweet cherry varieties was investigated by crossing experiments and molecular genetic analysis of two self-incompatibility loci. Crossing experiments included self- and cross-pollinations in the laboratory followed by microscopic observation of pollen tube growth and fruit set assay in the field. After crossing experiments, two accessions, 'Son Miró' and 'Talegal Ahín', were self-compatible while the other two were self-incompatible. Inheritance of S-locus and microsatellite EMPaS02 (linked to self-compatibility, Sc) were investigated in self-pollination progeny of both self-compatible genotypes. Results indicate that self-compatibility in 'Talegal Ahín' is similar to self-compatibility described in sweet cherry 'Cristobalina' and may be caused by the same mutation. That is a pollen part mutation not linked to the S-locus but linked to microsatellite EMPaS02 in cherry LG3. In 'Son Miró' self-compatibility seems more complex, affecting pollen and style function, and probably involving more than one mutation not described previously in sweet cherry. Together with 'Cristobalina', the newly described self-compatible varieties 'Son Miró' and 'Talegal Ahín' confirm the existence of unique self-compatible plant material in local germplasm from Spain that should be conserved and characterized for its use in breeding and research. [ABSTRACT FROM AUTHOR]

The Pyrus species exhibit the so-called S-RNase-based gametophytic self-incompatibility system, which is considered to be the most widespread self-incompatibility system among flowering plants. In this study, 57 Iranian pear ( Pyrus communis L.) domestic cultivars and wild genotypes, plus 21 European pear cultivars used as references, were genotyped adopting a PCR-based genotyping assay using consensus and allele-specific primers. The results revealed traces of significant genetic contribution in the Iranian traditional varieties and genotypes from other Pyrus species; the genetic contribution of Japanese pear clearly emerged with the detection of some Pyrus pyrifolia S-RNase alleles. Moreover, our results highlighted the presence of three new S-RNase alleles (named S, S, and S) that were not previously identified in P. communis, possibly introduced in the germplasm of cultivated pear through gene transfer from other cultivated or wild species. [ABSTRACT FROM AUTHOR]

European pear, as well as its close relatives Japanese pear and apple, exhibits S-RNase-based gametophytic self-incompatibility. The male determinant of this self-incompatibility mechanism is a pollen-expressed protein containing an F-box domain; in the genera Petunia (Solanaceae), Antirrhinum (Plantaginaceae), and Prunus (Rosaceae), a single F-box gene determines the pollen S. In apple and Japanese pear, however, multiple S-locus F-box genes were recently identified as candidates for the pollen S, and they were named S-locus F-Box Brothers. These genes were considered good candidates for the pollen S determinant since they exhibit S-haplotype-specific polymorphisms, pollen-specific expression, and linkage to the S-RNase. In the present study, S-locus F-Box Brothers homologs have been cloned from two of the most agronomically important European pear varieties, 'Abbé Fétel' (S/S) and 'Max Red Bartlett' (S/S), and they have been mapped on a genetic linkage map developed on their progeny. Our results suggest that the number of F-box genes linked to the S-locus of the European pear is higher than expected according with previous reports for apple and Japanese pear, since up to five genes were found to be linked to a single S-haplotype. Moreover, two of these genes exhibited an incomplete linkage to the S-RNase, allowing the identification of low-frequency recombinant haplotypes, generated by a crossing-over event between the two genes. These F-box genes are most likely placed in close proximity of the S-locus but do not belong to it, and they can thus be excluded from being responsible for the determination of pollen S function. [ABSTRACT FROM AUTHOR]

Sexual self-incompatibility in European pear ( Pyrus communis L.) is controlled by a single locus ( S-locus) encoding a polymorphic stylar ribonuclease ( S-RNase) that is responsible for the female function in pollen–pistil recognition. In this study, genomic DNA sequences corresponding to five new S-RNase alleles (named S 20 , S 21 , S 22 , S 23 , and S 24 ) and to S m were characterized in European pear cultivars. Re-sequencing S q from ‘General Le Clerc’ showed this S-RNase to encode the same protein as S 12 . Based on these findings, a polymerase chain reaction (PCR)-based method was developed for the molecular typing of cultivars bearing 20 S-RNases ( S 1 – S 14 , S m , and S 20 – S 24 ) using consensus and allele-specific primers. Genomic PCR with consensus primers amplified product sizes characteristic of the S-RNases S 1 , S 2 , S 4 , S 10 , S 13 , and S 20 . However, the allele groups S 3 / S 12 , S 6 / S 8 / S 11 / S 22 and S 5 / S 7 / S 9 / S 14 / S m / S 21 / S 23 / S 24 amplified PCR products of similar size. To discriminate between alleles within these groups, primers to specifically amplify each S-RNase were developed. Application of this approach in 19 cultivars with published S-alleles allowed re-evaluation of one of the alleles of ‘Passe Crassane,’ ‘Conference,’ and ‘Condo.’ Finally, this method was used to assign S-genotypes to 37 cultivars. Test crosses confirmed molecular results. [ABSTRACT FROM AUTHOR]