Assessment of Mating System in Helianthus annuus and H. petiolaris (Asteraceae) Populations

Abstract

Helianthus annuus subsp. annuus and H. petiolaris are wild NorthAmerican species that have been naturalized in central Argentina. They have asporophytic self-incompatibility genetic system that prevent self-fertilization butthe occurrence of self-compatible plants in Argentina was observed in bothspecies and could in part explain their highly invasive ability. Their geographicaldistribution coincides with the major crop area. The domestic sunflower is selfcompatible,can hybridize with both species and presents a considerable amountof gene flow. The aim of this study is to understand the self-incompatibilitymechanism in both wild Helianthus species. Reciprocal crossing and seed productionwere used to identify self-compatible genotypes, the number and distributionof self-incompatibility alleles within populations and the type and extent of allelicinteractions in the pollen and pistil. The behaviour of S alleles within eachpopulation was explained by five functional S alleles and one non-functionalallele in each species, differing in their presence and frequency within accessions.In both species, the allelic interactions were of dominance/recessiveness andcodominance in pollen, whereas it was only codominance in the pistil.Inbreeding effects in wild materials appeared in the third generation of selfpollination,with lethal effects in most plants. The number of S alleles is lowand they behave in a similar way of other Asteraceae species. The self-compatibilitywas addressed to non-functional S alleles introgressed in wild Helianthusplants through gene flow from self-compatible sunflower.