Abstract
The presence of self-incompatibility was tested in Centromadia pun gens subsp. laevis and the genetic basis of the self-incompatibility response was explored using crossing studies. We performed full diallel crossing experiments among 10 individuals from one natural population and four F1 families. We observed a strong self-incompatibility response in all individuals tested, with a significant difference in seed set between selfed and outcrossed matings. Most pairwise matings among parental plants were compatible, with some nonreciprocally incompatible matings (i.e., the matings were successful in one direction, but not the other), and only one reciprocally incompatible mating. The full diallel crossing studies among sibs in the four F1 families showed two major compatibility classes. These results are consistent with a single-locus sporophytic self-incompatibility system in this species.
Highlights
The majority of flow ering plants are hermaphroditi c, having both male and female floral organs
Self-incompatibility systems can be categorized into two basic types, gametophytic SI (GSI) and sporophytic SI (SSI)
There was no significant correlation between outcross seed set and selfed seed set for individual plants (r = -0.121, P = 0.75)
Summary
The majority of flow ering plants are hermaphroditi c, having both male and female floral organs. Self-incompatibility systems can be categorized into two basic types, gametophytic SI (GSI) and sporophytic SI (SSI). Several recent studies have suggested a breakdown of the SSI system, or the presence of additional loci controlling the response, suggesting that the SSI system within Asteraceae may not be as simple as previously thought (Les et al 1991; DeMauro 1993; Hiscock 2000b). These results serve as reminders that exhaustive studies are necessary in order to get a complete picture of the SI mechanism within any given family. Baldwin, which will be used as the model system for ongoing molecular and genetic studies of SI in Asteraceae subtribe Madiinae
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