Sex inheritance in gynodioecious species: a polygenic view

• Published in: Proceedings of the Royal Society. B, Biological sciences Vol. 272; no. 1574; pp. 1795 - 1802
• Main Authors: Ehlers, B.K, Maurice, S, Bataillon, T
• Format: Journal Article
• Language: English
• Published: London The Royal Society 07.09.2005; Royal Society, The
• Subjects: Alleles; Biodiversity and Ecology; Cytoplasm; Cytoplasmic Male Sterility; domain_sde.be.bp; Environmental Sciences; Female animals; Genotype; gynodioecy; hermaphrodites; inheritance (genetics); Likelihood Functions; Magnoliopsida - genetics; Magnoliopsida - physiology; mathematical models; maximum likelihood analysis; Modeling; Models, Genetic; Multifactorial Inheritance - genetics; Parametric models; Phenotypic traits; plant breeding; plant genetics; Plant reproduction; Plantago coronopus; Plants; Polygenic inheritance; Quantitative Threshold Model; Reproduction - physiology; Sex Determination; Sex Determination Processes; Sex ratio; Silene vulgaris; Species Specificity; Thymus vulgaris; quantitative threshold model; cytoplasmic male sterility; sex determination
• ISSN: 0962-8452; 1471-2954
• DOI: 10.1098/rspb.2005.3168

Gynodioecy is defined as the coexistence of two different sexual morphs in a population: females and hermaphrodites. This breeding system is found among many different families of angiosperms and is usually under nucleo-cytoplasmic inheritance, with maternally inherited genes causing male sterility and nuclear factors restoring male fertility. Numerous theoretical models have investigated the conditions for the stable coexistence of females and hermaphrodites. To date, all models rest on the assumption that restoration of a given male sterile genotype is controlled by a single Mendelian factor. Here, we review data bearing on the genetic determinism of sex inheritance in three gynodiecious plant species. We suggest that restoration of male fertility is probably best viewed as a quantitative trait controlled by many loci. We develop a threshold model that accommodates an underlying polygenic trait, which is resolved at the phenotypic level in discrete sexual morphs. We use this model to reanalyse data in Thymus vulgaris, Silene vulgaris and Plantago coronopus. A simple Mendelian inheritance of sex determinism is unlikely in all three species. We discuss how our model can shed additional light on the genetics of restoration and point towards future efforts in the modelling of gynodioecy.