The effect of root colonization by Glomus mosseae on the qualitative and quantitative pattern of essential oils (EO) was determined in three oregano genotypes (Origanum sp.). To exclude a simple P-mediated effect through mycorrhization the effect of P application to plants on the EO accumulation was also tested. In two genotypes the leaf biomass was increased through mycorrhization. Root colonization by the arbuscular mycorrhizal fungus (AMF) did not have any significant effect on the EO composition in oregano; however, in two genotypes the EO concentration significantly increased. As EO levels in P-treated plants were not enhanced, we conclude that the EO increase observed in mycorrhizal oregano plants is not due to an improved P status in mycorrhizal plants, but depends directly on the AMF-oregano plant association.

BACKGROUND: Garden sage (Salvia officinalis L., Lamiaceae) has gained importance during the last decade as a natural antioxidant, mainly owing to the antioxidant secondary plant metabolites rosmarinic acid (RA) and diterpenes such as carnosic acid. The aim of this work was to study the biomass production, the concentrations of total phenolics and RA and the essential oil of garden sage in response to phosphorus (P) supply. The treatments included P fertilisation and inoculation with arbuscular mycorrhizal fungi (AMF), since AMF are the most efficient biotic factor promoting the P uptake of plants.

The total phenolic and flavonoid contents and 2,2-diphenyl-1-picrylhydrazyl (DPPH) and ferric reduction antioxidant power (FRAP) antioxidant capacities of 19 accessions of Salvia officinalis from the sage collection of the genebank in Gatersleben (Germany) were evaluated. The major phenolic compounds of sage, that is, rosmarinic acid, caffeic acid, carnosol, and carnosic acid, were quantified by reverse-phase high-performance liquid chromatography. The aerial parts of different individual plants of each accession were collected in two consecutive years from the same experimental field at the beginning of their flowering period. The results demonstrated a high variability between accessions. A general decreasing tendency from 2007 to 2008 was observed in most of the estimated parameters, that is, total phenolic, total flavonoid, rosmarinic acid, and caffeic acid contents and DPPH antioxidant activity. A slight opposite trend was obtained with the FRAP antioxidant capacity. Low but variable quantities of carnosol and carnosic acid were evaluated in the sample extracts. Individual plants within accessions were identified with high phenolic content and strong antioxidant activity. The rosmarinic acid content showed up to 8-fold differences between the lowest and the highest values. Overall, the study demonstrated a high variability in secondary metabolites present in sage, which could be used for breeding of highly antioxidative genotypes of S. officinalis.