Trichome extracts from Nicotiana hybrids - a resource for testing disease/insect resistance
Glandular trichomes on the surface of species of the Solanaceae family produce sugar esters (SEs) that are species and cultivar-specific. SEs have insecticidal, antibiotic, and hormone-like properties, i.e. SE with medium-chain acyl groups (C7-C12) are more toxic to budworms, hornworms, aphids, whitefly, and bacteria. Sugar esters have great potential as a class of naturally occurring pesticides and antibiotics that degrade rapidly and are not known to be harmful to wildlife and other non-target organisms. Greater knowledge of the biological function of chemically-diverse sugar esters could assist the breeding programs and genetic engineering aiming to enhance crop protection using fewer synthetic pesticides.
Objective: The objective of this work was to analyze the acyl content of sugar esters from Nicotiana hybrids in search of unusual acyl compositions resulting from joint parental inheritance, and availability of abundant medium-chain length groups.
Methods: Nicotiana hybrids generated at KTRDC, Lexington, KY, USA, and a few commercial hybrids were grown in the green house. Trichome exudates from these were collected, and analyzed via GC-MS to identify their SE acyl profiles.
Results: Most of the hybrids inherited the profile of one parent but in one case a new composition was observed. Acyl profiles of two Turkish Samsun × N. benthamiana hybrids were very similar to the paternal profile (mostly 6- and 5-methylheptanoic acids). Production of SEs, however, was four fold higher than that of N. benthamiana. Additionally, certain commercial hybrids tested produced mainly octanoate and 2-methylbutyrate, similar to N. alata and N. sanderae, but in six fold higher quantity. Trichome extracts from micropropagated plants had a uniform qualitative profile.
Future work: Micropropagated plants will ensure sufficient accumulation of chemically-stable extracts for further tests against tobacco pests and diseases.