The genetic basis of a mutation that alters the floral symmetry in sunflower

Abstract

The indeterminate inflorescence of sunflower (Helianthus annuus) is heterogamous with zygomorphic ray flowers in the outer whorl of the head and actinomorphic disc flowers arrayed in arcs radiating from the centre of the head. The Chrysanthemoides (Chry) mutant is characterised by a change of the radially symmetric corolla of tubular disc flowers into a monosymmetric ligulate-like corolla. Zygomorphy is pronounced in the disc flowers placed on the peripheral whorls of inflorescences, while the monosymmetry is less marked toward the centre of the inflorescence. Although the Chry phenotype was one of first known morphological mutants in plants, studies on the genetic control of this trait are scarce and contradictory. Our results indicate that the Chry mutation is semidominant and exclude a maternal influence. Moreover, the data gathered in F 2 , BC 1 and F 3 progenies support a genetic model involving one major locus and an unknown number of modifiers. The improved knowledge on genetic control of the Chry mutation should enhance the introduction of this trait in crossbreeding programmes designed to produce new varieties of ornamental sunflower.

Mutations of corolla symmetry affect carpel and stamen development inHelianthus annuus

“…By contrast, Antirrhinum and Linaria mutations affecting floral symmetry showed no drastic effects on carpel development (Carpenter and Coen 1990;Luo et al 1996Luo et al , 1999Almeida et al 1997;Cubas et al 1999;Galego and Almeida 2002). In sunflower, the Chry mutation has been suggested to affect stamen development (Jaranowski et al 1977;Fambrini et al 2003a), as well as ovule formation in disk flowers of homozygous mutants (Fambrini et al 2003a). …”

“…A preliminary characterization (Fambrini et al 2003a) of homozygous Chry/Chry plants revealed a shift from the polysymmetric corolla typical of disk flowers to a monosymmetric ray-like corolla (Fig. 1e).…”

“…1e) shows a monosymmetric ray-like corolla in place of the polysymmetric corolla typical of disk flowers. Genetic analysis revealed the Chry phenotype to be controlled by a semidominant mutation (Fambrini et al 2003a). Zygomorphy is more pronounced in the disk flowers located in the peripheral whorls.…”

Utilization of related wild species (Echinacea purpurea) for genetic enhancement of cultivated sunflower (Helianthus annuus L.)

“…The number of ray (ligulate) flowers of the outer whorl of the head in H. annuus is genetically determined (Luczkiewicz 1975) and can be considered to be a specific qualitative trait characterizing putative hybrids (Fambrini et al 2003). Therefore, to determine the effect of the intergeneric cross, we evaluated the new sunflower lines by their morphological floral characteristics (Table 1).…”

Long Persistence and Other Aspects of Variants of False Mayweed, <em>Tripleurospermum maritima</em>, at Sackville, New Brunswick

“…Total variant plants found per year ranged from 28 (2007) to 103 (2008), the largest number following the most drastic disturbance. The site may have received toxic waste disposal causing a mutation that resulted in persisting aberrations not unlike some reported for other Asteraceae (Fambrini et al 2003).…”