Luciana G. Angelini

Industrial hemp (Cannabis sativa L.), being a multiharvest crop, can increase farm profitability and cropping system diversification, including in marginal areas. Since inflorescence essential oil (EO) represents a valuable co-product for cosmetics and pharmaceutical sectors, the aim of this study was to assess the effect of pedoclimatic conditions on the inflorescence yield. EO content, composition and antioxidant capacity of the monoecious variety ‘Futura 75’. So, on-farm trials were performed in central Italy at three sites (SL, LA and SPG), which differed in terms of soil (taxonomic classes; chemical and physical characteristics), microclimate conditions (rainfall and air temperatures) and agricultural value. The results highlighted how location specificities significantly influence crop performance. Strong differences in productive parameters were observed among the farms, with inflorescence yields ranging from 1.3 to 4.9 Mg ha−1, mainly depending on the differences between the maximum and minimum air temperatures (ΔT) since negative correlations were found. Similarly, the concentration of monoterpene and sesquiterpene hydrocarbons showed a reduction when ΔT during the studied period was higher; conversely, oxygenated sesquiterpenes showed an increment due to a higher ΔT. Only phenylpropanoids were affected by rainfall, showing a positive correlation. All these findings confirm that in hemp, satisfactory productions can be reached only by matching territorial suitability. The variability in EO’s characteristics suggests, in fact, that the “uniqueness” of the EOs derives from a combination of the pedological, climatic and agronomic variables of each site.

Stevia rebaudiana (Bertoni) is a highly valuable crop for the steviol glycoside content in its leaves, which are no-calorie sweeteners hundreds of times more potent than sucrose. The presence of health-promoting phenolic compounds, particularly flavonoids, in the leaf of S. rebaudiana adds further nutritional value to this crop. Although all these secondary metabolites are highly desirable in S. rebaudiana leaves, the genes regulating the biosynthesis of phenolic compounds and the shared gene network between the regulation of biosynthesis of steviol glycosides and phenolic compounds still need to be investigated in this species. To identify putative candidate genes involved in the synergistic regulation of steviol glycosides and phenolic compounds, four genotypes with different contents of these compounds were selected for a pairwise comparison RNA-seq analysis, yielding 1136 differentially expressed genes. Genes that highly correlate with both steviol glycosides and phenolic compound accumulation in the four genotypes of S. rebaudiana were identified using the weighted gene co-expression network analysis. The presence of UDP-glycosyltransferases 76G1, 76H1, 85C1, and 91A1, and several genes associated with the phenylpropanoid pathway, including peroxidase, caffeoyl-CoA O-methyltransferase, and malonyl-coenzyme A:anthocyanin 3-O-glucoside-6″-O-malonyltransferase, along with 21 transcription factors like SCL3, WRK11, and MYB111, implied an extensive and synergistic regulatory network involved in enhancing the production of such compounds in S. rebaudiana leaves. In conclusion, this work identified a variety of putative candidate genes involved in the biosynthesis and regulation of particular steviol glycosides and phenolic compounds that will be useful in gene editing strategies for increasing and steering the production of such compounds in S. rebaudiana as well as in other species.