Phenotypic diversity in cell wall lignocellulosic constituents and ethanol yield of USDA guayule and mariola germplasm

Authors: Abdel-Haleem, Hussein; Masterson, Steven; Sedivy, Aaron; Mitchell, Robert

Submitted to: Plants
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/16/2025
Publication Date: 4/18/2025
Citation: Abdel-Haleem, H.A., Masterson, S.D., Sedivy, A.M., Mitchell, R. 2025. Phenotypic diversity in cell wall lignocellulosic constituents and ethanol yield of USDA guayule and mariola germplasm. Plants. https://doi.org/10.3390/plants14081239.
DOI: https://doi.org/10.3390/plants14081239

Interpretive Summary: The current study aimed at identifying components from guayule that could be used as intermediates chemicals for the emerging bioeconomy. To achieve that target, phenotypic diversity in lignocellulosic components in the USDA guayule and mariola collections were explored. Wide ranges in compositional components and yield indicated the high phenotypic diversity in the studied traits, reflecting different origins, adaptations and genetic makeups of those genotypes. Several genotypes were identified with high yield stability when grown under contrasting environments and high responses to drought stress (less irrigation) conditions. Those genotypes could be parental materials to improve bioenergy-related traits in guayule. These findings are laying the foundation for guayule breeding efforts to select parental candidates for breeding programs to grow guayule under different growing conditions and to achieve multiple production goals.

Technical Abstract: Guayule (Parthenium argentatum A. Gray) is a valuable domestic source for rubber and resin. At its center of origin at northern Mexico and southern Texas deserts, guayule, a perennial shrub, is hybridized with its relative species mariola (Parthenium incanum Kunth). As rubber and resin are the main products from guayule, there is interest to use guayule bagasse as a bioenergy feedstock to meet the growing bioenergy and biofuel demands. This study aimed to explore and characterize phenotypic diversity in cell wall constituents (lignin, cellulose, and hemicellulose) and their yields among 51 guayule and mariola genotypes under two irrigation regimes (well-watered and water-stressed). Significant genotypic and environmental effects were observed for lignin, cellulose and hemicellulose concentrations and yields indicating the wide genetic variability of the collection for bioenergy-related traits. Moderate to high entry-mean heritability values for lignin, cellulose, and hemicellulose suggest that selection is feasible to enhance genetic gain. Significant positive correlations were found among cellulose and hemicellulose concentrations and yields, indicating the possibility to select for multiple traits together during breeding cycles. High positive correlations between rubber and resin and lignin, cellulose and hemicellulose yields highlight the opportunity to develop guayule germplasm with enhanced multi-use traits for industrial applications. Wide variations in drought stress indices (stress tolerance index, yield index and yield stability index) underscores the environmental impact on the lignocellulosic traits. Several genotypes were identified with high stress index scores and could be parental candidates for improving guayule for arid and semi-arid sustainable agricultural systems. The current study is the first to characterize the phenotypic diversities in guayule and mariola for lignocellulosic components and yield, providing the foundation for future breeding efforts aimed at enhancing guayule’s value for diverse production goals and environmental conditions.