Bioprospecting for improved floral fragrance in wild sunflowers

Abstract

Abstract Cultivated sunflower (Helianthus annuus) is not typically considered to have a pleasant floral fragrance. In field production, seed yield is often limited by pollination services, particularly in the production of hybrid seed. Improved floral fragrance, as determined by volatile organic compounds, may be a route to improving pollinator attraction for oilseed and confectionary production and could also add value to ornamental sunflowers. Wild relatives of H. annuus have a long history of being used to breed improved traits into cultivated varieties, yet it is unknown whether favorable scents are present in wild Helianthus species and thus an available resource for fragrance breeding. In order to assess the diversity of floral fragrance available in crop wild relatives, 30 diverse accessions of wild Helianthus as well as seven varieties of H. annuus spanning a domestication gradient were grown in greenhouse experiments and variation in floral volatiles was analyzed by solid phase microextraction-gas chromatography-mass spectrometry. While alpha-pinene made up a significant portion of the volatiles emitted for most taxa, there was substantial diversity present across the genus as well as within H. annuus. Most volatiles emitted were monoterpenoids with a significant share of sesquiterpenoids. The diversity identified here will inform further targeted study of which compounds affect pollinator attraction and health. Several wild accessions such as Helianthus debilis subsp. tardiflorus and Helianthus praecox subsp. praecox as well as open-pollinated domesticated accessions of H. annuus show promise for breeding for improved floral fragrance due to high volatile abundance and likely favorable compound compositions.