Abstract Detail

Molecular Ecology and Evolution

Montgomery, Benjamin R. [1], Delph, Lynda [2].

Assessment of costs of restoration in Brassica napus, a crop plant that exhibits cytoplasmic male sterility.

For plants that exhibit cytonuclear gynodioecy, an individual carrying a mitochondrial cytoplasmic male sterility (CMS) gene is rendered male sterile, but fertility may be restored by activity of a nuclear restorer gene. Models suggest that maintenance of cytonuclear gynodioecy in populations lacking spatial structure requires that nuclear restorer alleles incur a cost under some conditions; otherwise, such alleles would only experience neutral or positive selection and tend toward fixation. Tests of costs of restorer alleles in natural populations have been limited, in part because the underlying genetics are poorly understood. We take advantage of a well characterized CMS-like system in a crop plant, Brassica napus, in order to measure aspects of fitness in four lineages that varied in whether they carried the pol CMS gene or no restorer (cam) and whether they carried one copy of the pol restorer, Rfp, or the nap CMS restorer, Rfn, along with one non-restoring allele, rf. Plants with pol CMS and a non-restoring nuclear genotype (pol rf/Rfn) showed reductions in petal display, pollen counts, and stamen length, indicative of reduced male fertility, in comparison with plants with cam cytoplasm or restored pol cytoplasm. Indicative of incomplete restoration, plants with restored pol cytoplasm (pol rf/Rfp) showed reductions in petal display and stamen length compared to genotypes with cam cytoplasm (cam rf/Rfn and cam rf/Rfp), and a reduction in pollen counts compared to the latter cam genotype. Between the genotypes with cam cytoplasm, stamen length and pollen production were significantly greater for plants with the Rfp than Rfn restorer. In this comparison, the restorers were in genetically similar plants that lacked a CMS gene, so differences in the stamen indicate that these restorer alleles have other effects on floral phenotypes beyond restoration of male fertility. Any effects, such as reduced pollen counts, that translate into lower fitness represent a cost of the restorer gene. Lower pollen production in plants with the Rfn versus the Rfp restorer may be explained by Rfn affecting the expression of more mtDNA regions than does Rfp.

Broader Impacts:

1 - University of South Carolina Upstate, Natural Sciences and Engineering, 800 University Way, Spartanburg, SC, 29303, USA
2 - Indiana University, Department of Biology, Jordan Hall, 1001 East Third Street, Bloomington, IN, 47405, USA

Keywords:
cytoplasmic male sterility
cost of fertility restoration
Brassica napus
gynodioecy.

Presentation Type: Oral Paper:Papers for Topics
Session: 46
Location: Newberry/Riverside Hilton
Date: Wednesday, July 31st, 2013
Time: 1:45 PM
Number: 46002
Abstract ID:868
Candidate for Awards:None