| Abstract Detail
Conference Wide Covey, Paul A. [1], Denney, Ashley S. [2], Martini, Dyllon I. [2], Bedinger, Patricia [1]. High levels of S-RNase expression are not required for unilateral incongruity in the tomato clade. POLLEN rejection by pistils can occur if the pollen is too closely related to the pistil (self-incompatibility, SI) or if it is too distantly related, for example from a different species. Many plant families exhibit interspecific incongruity in one direction, i.e. the pistils of one species will accept pollen of another species but not vice versa, a phenomenon known as unilateral incongruity (UI). In the tomato clade, pistils of the domesticated species Solanum lycopersicum can accept pollen from eight closely related wild species, but in many cases the pistils of these wild species will reject pollen from S. lycopersicum. SI in tomato is based on two S-locus genes; pistil expressed cytotoxic S-RNase genes and pollen expressed F-box genes. The purpose of our experiments was to determine whether S-RNases are also required for pollen rejection in UI. We tested pistil extracts from both self compatible (SC) and self incompatible (SI) accessions of S. pennellii, S. habrochaites, and S. chmielewskii for S-RNase activity, and we examined S. lycopersicum pollen tube growth in pistils of the same species. We found high levels of S-RNase activity in pistils of all SI accessions, as expected. In SC accessions of wild species, S-RNase was not detected. Pistils of all accessions of S. pennellii, S. habrochaites, and S. chmielewskii were able to reject S. lycopersicum pollen, regardless of whether the accessions were SI or SC. In S. pennellii and S. habrochaites pistils, pollen rejection occurred in the upper ¼ of the pistil, whereas in S. chmielewskii pollen tubes grew to about ¾ of the length of the pistil. Our results indicate that interspecific barriers to reproduction in the tomato clade are not dependent on high levels of S-RNase expression in pistils. Thus, the mechanisms of pollen rejection in self-incompatibility and unilateral incongruity are likely to be different.
Log in to add this item to your schedule
1 - Colorado State University, Biology, Fort Collins, CO, 80523-1878, USA
2 -
Keywords:
tomato
Wild Solanum species
unilateral incongruity
reproductive barriers
pollen-pistil interactions.
Session: Poster-145
Location: Ballroom CD/Monona Terrace
Date: Tuesday, July 25th, 2006
Time: 8:00 AM
Abstract ID:347 |
