¹Department of Biological Sciences, Vanderbilt University, Nashville, TN, USA

Correspondence: JR Ellis, Department of Biological Sciences, Vanderbilt University, VU Station B 351634, 465 21st Avenue South, Nashville, TN 37232, USA. E-mail: jennifer.ellis@vanderbilt.edu

Received 21 November 2007; Revised 15 January 2008; Accepted 18 January 2008; Published online 27 February 2008.

Abstract

A variety of questions in population and evolutionary biology are studied using chloroplast DNA (cpDNA). The presumed maternal inheritance in angiosperms allows for certain assumptions and calculations to be made when studying plant hybridization, phylogeography, molecular systematics and seed dispersal. Further, the placement of transgenes in the chloroplast to lessen the probability of 'escape' to weedy relatives has been proposed since such genes would not move through pollen. In many studies, however, strict maternal inheritance is assumed but not tested directly, and some studies may have sample sizes too small to be able to detect rare paternal leakage. Here, we study the inheritance of cpDNA simple sequence repeats in 323 offspring derived from greenhouse crosses of the rare sunflower Helianthus verticillatus Small. We found evidence for rare chloroplast paternal leakage and heteroplasmy in 1.86% of the offspring. We address the question of whether one can extrapolate the mode of chloroplast transmission within a genus by comparing our results to the findings of another sunflower species study. The findings of occasional paternal transmission of the chloroplast genome are discussed in the framework of using these markers in studies of population and evolutionary biology both in Helianthus and other angiosperms.