Expression and inheritance of sporophytic self-incompatibility in synthetic allohexaploid Senecio cambrensis (Asteraceae)
Author for correspondence:
Simon J. Hiscock
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- •Allopolyploid speciation is common in plants and is frequently associated with shifts from outcrossing, for example self-incompatibility, to inbreeding (i.e. selfing). Senecio cambrensis is a recently evolved allohexaploid species that formed following hybridization between diploid self-incompatible S. squalidus and tetraploid self-compatible S. vulgaris. Studies of reproduction in wild populations of S. cambrensis have concluded that it is self-compatible.
- •Here, we investigated self-compatibility in synthetic lines of S. cambrensis generated via hybridization and colchicine-induced polyploidization and wild S. cambrensis using controlled crossing experiments.
- •Synthetic F1S. cambrensis individuals were all self-compatible but, in F2 and later generations, self-incompatible individuals were identified at frequencies of 6.7–9.2%. Self-incompatibility was also detected in wild sampled individuals at a frequency of 12.2%. The mechanism and genetics of self-incompatibility were tested in synthetic S. cambrensis and found to be similar to those of its paternal parent S. squalidus (i.e. sporophytic).
- •These results show, for the first time, that functional sporophytic self-incompatibility can be inherited and expressed in allopolyploids as early as the second (F2) generation. Wild S. cambrensis should therefore be considered as possessing a mixed mating system with the potential for evolution towards either inbreeding or outcrossing.