Profile and accumulation of essential oils from guayule (Parthenium argentatum A. Gray) accessions and hybrids

For guayule (Parthenium argentatum A. Gray) to become a viable market option, it will be necessary to exploit not only the rubber and resin components, but also other high-value plant products such as essential oils (EOs). A detailed EO profiling study was conducted on 16 guayule accessions for first time, which revealed significant differences in EO yield and profile among them. Accession AZ-2 had the highest yield up to 0.9% (dry weight), followed by CFS18–2005, CAL-7, and CFS17–2005. These yields were comparable with those of aromatic plants used in the industry, providing valuable economic insights. The volatile EO composition of the accessions was unique and discriminating. Volatile sesquiterpenes were the most abundant compounds at the beginning of the flowering stage (S1-June sampling), while monoterpenes became more abundant as flowering progressed (S2-July and S3-August sampling). At S1, it was possible to distinguish between hybrid (mariola and non-mariola) and other accessions by the EO profile. By the end of the summer season (S3, August 2023), the EO volatile profile could more easily distinguish the accessions according to their genetic origin, enabling the separation of pure guayule accessions. The extraction of guayule EOs on an industrial scale (1.2 Mg fresh biomass) demonstrated high yield and consistency in terms of volatile profile, underscoring its potential for commercial exploitation.