Female and hermaphrodite flowers on a chimeric gynomonoecious Silene vulgaris plant produce offspring with different genders: A case of heteroplasmic sex determination?

Abstract

In gynodioecious plant species, individuals have either female or hermaphrodite flowers. However, individuals with both types of flowers, that is, 'gynomonoecious' or 'partially male steriles,' are sometimes found. The standard explanation of gynomonoecious individuals is that their male- sterilizing cytoplasm is incompletely restored by nuclear male fertility genes. Silene vulgaris, the bladder campion, is usually referred to as being gynodioecious, though gynomonoecious individuals have frequently been observed. In an attempt to determine if the segregation of flower types on gynomonoecious plants of S. vulgaris is associated with a difference in offspring gender, a series of crosses was performed. The results show that female and hermaphroditic flowers on the same plant produce offspring of all three types, but the frequencies with which they do so differ. If incomplete restoration was the relevant explanation in this case, these results would not have occurred. Instead an intraindividual segregation of one or many genetic factors that affect the sexual phenotype of flowers and their subsequent offspring is proposed.