GENETICS AND BIOCHEMISTRY OF FLOWER COLOR IN STOKES ASTER

A study was conducted to investigate the genetics and biochemistry of flower color in stokes aster (Stokesia laevis). HPLC analysis of cultivars with pale blue (‘Omega Skyrocket’, ‘Blue Danube’), lavender (‘Peaches’), or violet flowers (‘Honeysong Purple’, ‘Purple Parasols’) indicated that petunidin was the principal anthocyanidin responsible for these flower colors. Albescent flowers of ‘Alba’ also contained petunidin, but at a substantially lower concentration. Pale magenta flowers of ‘Maroon’ and ‘Colorwheel’ primarily contained cyanidin. The aglycone of luteolin, a common flavone, was identified in all cultivars that were tested. Pale yellow flowers of ‘Mary Gregory’ did not contain anthocyanins or carotenoids, suggesting that its flower color may be attributable to a yellow-colored form of luteolin. F₁ and F₂ families derived from controlled hybridizations were used to investigate the inheritance of flower color. All F₁ progeny resulting from hybridizations of pale blue, lavender, violet, pale yellow, pale magenta, and albescent-flowered parents had only blue or lavender flowers. This suggests that blue or lavender flower color is dominant to all other colors. The F₂ progeny from ‘Alba’ (albescent) x ‘Blue Danube’ (blue) segregated in a 3:1 ratio (blue:albescent), suggesting that albescence or reduced pigmentation is controlled by a single recessive gene. Two independent F₂ families were generated from the hybridization of ‘Mary Gregory’ (pale yellow) with either ‘Omega Skyrocket’ (blue) or ‘Alba’ (albescent). Pale yellow-flowered progeny were recovered in the F₂ family derived from ‘Alba’ (albescent) x ‘Mary Gregory’ (yellow), but not from the F₂ family derived from ‘Mary Gregory’ (pale yellow) x ‘Omega Skyrocket’ (blue). This shows that yellow flower color is heritable, but its expression is restricted to certain genetic backgrounds.

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