Eucalyptus sideroxylon A. Cunn.: A Natural Eucalyptol (1,8-cineole) source in Morocco

The main objective of this work is to determine the effect of the harvest period on the yield and chemical quality of the essential oils of the Eucalyptus sideroxylon A. Cunn. leaves of the Mamora forest, Dayet Zerzour Bnifdel region, Rabat. Essential oil yields are remarkably high above 2.3%, with an ultimate rate of 5.48% for the month of April. The chemical quality of these essential oils is characterized by the presence of two major monoterpenes, 1,8-cineole (eucalyptol) and α-terpineol, which are proportionally inverted in terms of quantity. During the wet months between September and March, the cineole predominates with levels ranging from 72.67% to 86.11% and the other dry months are characterized by an increase of α-terpineol rate from 12.05% to 25.61%. This inverted chemical variability reveals a change in the orientation of cineole and α-terpineol biosynthesis under the control of climatic factors. This work allows us to discern favorable periods for the harvest of Eucalyptus sideroxylon leaves in terms of yield and quality of essential oils.

HPLC-PDA-ESI-MS/MS Profiling and Anti-Biofilm Potential of Eucalyptussideroxylon Flowers

The development of multidrug-resistant bacterial strains is a worldwide emerging problem that needs a global solution. Exploring new natural antibiofilm agents is one of the most important alternative therapies in combating bacterial infections. This study aimed at testing the antimicrobial potential of Eucalyptus sideroxylon flowers extract (ESFE) against Bacillus subtilis, Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa and Candida albicans prior to testing the antibiofilm activity against S. aureus, P. aeruginosa and C. albicans. ESFE demonstrated antimicrobial activity and promising inhibition activity against methicillin-resistant S. aureus (MRSA) biofilm formation up to 95.9% (p < 0.05) at a concentration of 0.05 mg/mL and eradicated C. albicans biofilm formation up to 71.2% (p < 0.05) at a concentration of 0.7 mg/mL. LC-MS analysis allowed the tentative identification of eighty-three secondary metabolites: 21 phloroglucinol, 18 terpenes, 16 flavonoids, 7 oleuropeic acid derivatives, 7 ellagic acid derivatives, 6 gallic acid derivatives, 3 phenolic acids, 3 fatty acids and 2 miscellaneous. In conclusion, E. sideroxylon is a rich source of effective constituents that promote its valorization as a promising candidate in the management of multidrug-resistant bacterial infections.

Landscape drivers of genomic diversity and divergence in woodland Eucalyptus

Spatial genetic patterns are influenced by numerous factors, and they can vary even among coexisting, closely related species due to differences in dispersal and selection. Eucalyptus (L’Héritier 1789; the “eucalypts”) are foundation tree species that provide essential habitat and modulate ecosystem services throughout Australia. Here we present a study of landscape genomic variation in two woodland eucalypt species, using whole genome sequencing of 388 individuals of Eucalyptus albens and Eucalyptus sideroxylon. We found exceptionally high genetic diversity (π ≈ 0.05) and low genome-wide, inter-specific differentiation (FST = 0.15). We found no support for strong, discrete population structure, but found substantial support for isolation by geographic distance (IBD) in both species. Using generalised dissimilarity modelling, we identified additional isolation by environment (IBE). Eucalyptus albens showed moderate IBD, and environmental variables have a small but significant amount of additional predictive power (i.e., IBE). Eucalyptus sideroxylon showed much stronger IBD, and moderate IBE. These results highlight the vast adaptive potential of these species, and set the stage for testing evolutionary hypotheses of interspecific adaptive differentiation across environments.

Impact of competition from coppicing stumps on the growth of retained trees differs in thinned Eucalyptus globulus and Eucalyptus tricarpa plantations in southeastern Australia

Coppice growth on cut stumps in thinned Eucalyptus plantations has the potential to compete with and reduce the growth of retained sawlog crop trees (SCTs). This study examined to what extent SCT growth was reduced by coppice in two stands in southeastern Australia: (i) a Eucalyptus globulus Labill. plantation thinned at age 10 years and (ii) a slower growing Eucalyptus tricarpa L.A.S. Johnson & K. Hill (syn. Eucalyptus sideroxylon subsp. tricarpa L.A.S. Johnson) plantation thinned at age 62 years. After 5 years, thinning E. globulus from 850 to 400 trees·ha–1 increased the basal area of the largest diameter 200 SCTs·ha–1 (SCT200) by 11% when coppice was removed. There was no significant thinning response by SCT200 when coppice was retained. After 10 years, thinning E. tricarpa from about 600 to 100 trees·ha–1 increased the basal area of the largest diameter 100 SCTs trees·ha–1 (SCT100) by about 10% whether coppice was removed or not. At the time of measurement, coppice contributed 17% and 36% of stand sapwood area in thinned E. globulus and E. tricarpa treatments, respectively, and possibly competed with SCTs for water. This study shows the significant competitive effect that coppice can have in thinned eucalypt plantations and the importance of coppice management to the growth of retained trees.