title: Diversity of S-alleles and mate availability in 3 populations of self-incompatible wild pear (Pyrus pyraster).
abstract: Small populations of self-incompatible plants may be expected to be threatened by the limitation of compatible mating partners (i.e., S-Allee effect). However, few empirical studies have explicitly tested the hypothesis of mate limitation in small populations of self-incompatible plants. To do so, we studied wild pear (Pyrus pyraster), which possesses a gametophytic self-incompatibility system. We determined the S-genotypes in complete samplings of all adult trees from 3 populations using a PCR-RFLP approach. We identified a total of 26 different S-alleles, homologous to S-alleles of other woody Rosaceae. The functionality of S-alleles and their Mendelian inheritance were verified in artificial pollination experiments and investigations of pollen tube growth. The smallest population (N = 8) harbored 9 different S-alleles and showed a mate availability of 92.9%, whereas the 2 larger populations harbored 18 and 25 S-alleles and exhibited mate availabilities of 98.4% and 99.2%, respectively. Therefore, we conclude that even small populations of gametophytic self-incompatible plants may exhibit high diversity at the S-locus and are not immediately threatened owing to reduced mate availability.
authors.affiliation: WSL Swiss Federal Research Institute, Zürcherstrasse 111, CH-8903 Birmensdorf, Switzerland.
authors.forename: S E
authors.initials: SE
authors.lastname: Hoebee
authors.forename: S
authors.initials: S
authors.lastname: Angelone
authors.forename: D
authors.initials: D
authors.lastname: Csencsics
authors.forename: K
authors.initials: K
authors.lastname: Määttänen
authors.forename: R
authors.initials: R
authors.lastname: Holderegger
mesh_terms: D000483:Alleles; D001483:Base Sequence; D019295:Computational Biology; D014644:Genetic Variation; D005838:Genotype; D007178:Inbreeding; D008856:Microscopy, Fluorescence; D008969:Molecular Sequence Data; D053205:Pollen Tube / Q000648:ultrastructure; D016133:Polymerase Chain Reaction; D011156:Population Density; D031989:Pyrus / Q000235:genetics*; D017422:Sequence Analysis, DNA; D013557:Switzerland