Genetics. Published Articles Ahead of Print: June 18, 2008, Copyright © 2008
doi:10.1534/genetics.107.083618


A more recent version of this article appeared on July 1, 2008.

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Comparative genetics of hybrid incompatibility: sterility in two Solanum species crosses

Leonie C Moyle 1* and Takuya Nakazato 1

1 Indiana University

* To whom correspondence should be addressed. E-mail: lmoyle{at}indiana.edu.

Submitted on October 21, 2007
Revised on February 7, 2008
Accepted on 28 April 2008


Abstract

The genetic basis of hybrid sterility can provide insight into the genetic and evolutionary origins of species barriers. We examine the genetics of hybrid incompatibility between two diploid plant species in the plant clade Solanum sect. Lycopersicon. Using a set of near-isogenic lines (NILs) representing the wild species Solanum pennellii (formerly Lycopersicon pennellii) in the genetic background of the cultivated tomato S. lycopersicum (formerly L. esculentum), we found: hybrid pollen and seed infertility are each based on a modest number of loci; male (pollen) and other (seed) incompatibility factors are roughly comparable in number; and, seed infertility QTL act additively or recessively. These findings are remarkably consistent with our previous analysis in a different species pair, S. lycopersicum x S. habrochaites. Data from both studies contrast strongly with data from Drosophila. Finally, QTL for pollen and seed sterility from the two Solanum studies were chromosomally co-localized, indicating a shared evolutionary history for these QTL, a non-random genomic distribution of loci causing sterility, and/or a proclivity of certain genes to be involved in hybrid sterility. We show that comparative mapping data can delimit the probable timing of evolution of detected QTL, and discern which sterility loci likely evolved earliest among species.

Key Words: Lycopersicon esculentum, plant, reproductive isolation, snowball effect, speciation