The effect of sheltered load on reproduction in Solanum carolinense, a species with variable self-incompatibility

J.I. Mena-Ali, L.H. Keser, A.G. Stephenson

Research output: Contribution to journalArticleAcademicpeer-review

11 Citations (Scopus)

Abstract

In previous studies, we have investigated the strength of self-incompatibility (SI) in Solanum carolinense, a highly successful weed with a fully functional SI system that inhabits early successional and other disturbed habitats. We have found that the SI response in S. carolinense is a plastic trait—its strength being affected by the age of the flowers, and the presence of developing fruits and that there are genetic differences among families in their self-fertility. However, in species with a fully functional SI response, selfing would not be that common. As a result, deleterious recessives scattered though the genome of horsenettle are only occasionally exposed to selection. It has been suggested that deleterious recessives accumulate near S-alleles in strong SI species because the S-locus is located in a non-recombining region of the genome and because strong S-alleles are never in the homozygous state, thus sheltering some of the genetic load near the S-locus from selection. We performed a series of laboratory and greenhouse experiments to determine the extent to which sheltered load adds to the overall magnitude of inbreeding depression in horsenettle. Specifically, we amplified and sequenced the S-alleles from 16 genets collected from a large population in Pennsylvania and performed a series of controlled self-pollinations. We then grew the selfed progeny in the greenhouse; recorded various measures of growth and reproductive output; and amplified and sequenced their S-allele(s). We found that the heterozygous progeny of self-pollinations produce more flowers and have a greater ability to set both self and cross seed than S-homozygous progeny. We also found evidence of variation in the magnitude of load among S-alleles. These results suggest that sheltered load might slow the fixation of weak (partially compatible) S-alleles in this population, thus adding to the maintenance of a mixed mating system rather than leading to the fixation of the selfing alleles
Original languageEnglish
Pages (from-to)63-71
JournalSexual Plant Reproduction
Volume22
Issue number2
DOIs
Publication statusPublished - 2009

Keywords

  • pollen-tube growth
  • inbreeding depression
  • flowering plants
  • natural-populations
  • nicotiana-alata
  • s-alleles
  • evolution
  • solanaceae
  • model
  • fertilization

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