Effect of harvest time and low water availability during balsamic period on Salvia officinalis L. biomass development, ecophysiological traits and essential oil yield and composition

Sage (Salvia officinalis L.) is cultivated in many countries due to the medicinal and industrial importance of its essential oil (EO). The yield and quality of the crops to be included in the medicinal plant supply chain should be constant, but often this is not the case since they are both influenced by environmental variability and crop management. We therefore studied the influence of water availability and harvest time, during the balsamic period, on a sage crop cultivated at an experimental field site in the Molise Region (South-central Italy), evaluating the main agronomic and ecophysiological traits in terms of plant biomass production and photosynthetic performance. The yield and composition of the essential oils, extracted by hydrodistillation and analyzed by GC and CG/MS, were also evaluated. The well-watered crops harvested 42 days after beginning of flowering, exhibited higher dry biomass yield than rainfed plants as well as higher values of relative water content, photosynthesis and leaf CO2 conductance. Instead, at the same time (after 42 days) the EO content was higher in rainfed plants then in well-watered ones, in which it remained constant throughout all the harvesting period. All the EOs were rich in bioactive compounds such as α-thujone, β-thujone, camphor and borneol, but only in well-watered plants the content was constant throughout all the harvesting periods. In fact, the EO of rainfed plants analyzed over the harvest time was mainly rich at the beginning in camphor and borneol, whereas in the middle in α-thujone. Our study demonstrates that the crop performance is greatly influenced by the water availability during the balsamic period. The results of this study provide new knowledge to produce sage oil of adequate quality for the different uses.