Establishment and antifungal potential of in vitro biomass of Salvia somalensis

Carnosic acid, a well-known abietane diterpenoid produced by several Salvia spp., including S. somalensis, has shown potential as an agrochemical for the treatment of several phytopathogenic fungi [1]. Aim of this project was to establish micropropagated plants from S. somalensis, to assess their production of carnosic acid and to investigate the antifungal activity against common plant pathogens. Explants placed in medium containing the growth regulators, 0.5 mg/L BA plus 0.1 mg/L NAA, produced an average of 7.43 shoots per explant. The methanolic extracts of the aerial parts and micropropagated plants (MP) of S. somalensis were characterized by LC-MS analysis. Both produced carnosic acid, as well as carnosol, 12-methylcarnosic acid, 20-deoxocarnosol, and other terpenoids. The antifungal activity of the two extracts was assessed against Rhizoctonia solani, Fu- sarium solani, Colletotrichum coccodes, Sclerotinia sclerotiorum, and Botrytis cinerea. The extract of the in vivo biomass was active against all the fungi tested. The activity at 1000 μg/mL against F. solani, B. cinerea, and C. coccodes (72%, 84%, and 86% inhibition of mycelial growth, respective- ly) was statistically comparable to the activity of the reference commercial fungicides Ortiva® and Switch® (Syngenta), applied at 1000 μg/mL. The extract of the MP at 1000 μg/mL was active against B. cinerea, R. solani, C. coccodes, and S. sclerotiorum (63%, 69%, 63% and 62% inhibition of my- celial growth, respectively). Although the antifungal activity of the MP was statistically lower than the in vivo biomass, the results confirmed the significance of MP as a source of bioactive compounds of agricultural interest.