1. ¹Department of Biological Sciences, University of Illinois-Chicago, Chicago, IL, USA
2. ²Department of Biology, Washington University, St Louis, MO, USA
3. ³Section of Ecology, Behavior and Evolution, Division of Biological Sciences, University of California San Diego, La Jolla, CA, USA

Correspondence: Professor B Igic, Department of Biological Sciences, University of Illinois-Chicago, M/C 067, 840 West Taylor Street, Chicago, IL 60607, USA. E-mail: boris@uic.edu

⁴These authors contributed equally to this work.

Received 8 January 2007; Revised 15 June 2007; Accepted 20 June 2007; Published online 15 August 2007.

Abstract

We characterized the molecular allelic variation of RNases at the self-incompatibility (SI) locus of Solanum chilense Dun. We recovered 30 S-RNase allele sequences from 34 plants representing a broad geographic sample. This yielded a species-wide estimate of 35 (95% likelihood interval 31–40) S-alleles. We performed crosses to confirm the association with SI function of 10 of the putative S-RNase allele sequences. Results in all cases were consistent with the expectation that these sequences represent functional alleles under single-locus gametophytic SI. We used the allele sequences to conduct an analysis of selection, as measured by the excess of nonsynonymous changes per site, and found evidence for adaptive changes both within the traditionally defined hypervariable regions and downstream, near the 3'-end of the molecule.