Nanoactivities of natural nanomaterials rosmarinic acid, glycyrrhizic acid and glycyrrhizic acid ammonium salt against tomato phytopathogenic fungi Alternaria alternata and Penicillium digitatum

Black mold and green mold caused by Alternaria alternata and Penicillium digitatum, respectively,are the most important decay pathogens of tomato fruits during storage. Ourresearch was aimed to control tomato phytopathogenic fungi A. alternata and P. digitatumin vitro and in vivo by using natural nanomaterials rosmarinic acid (RA-NPs) at concentrationsof 0.3 and 0.6 mM, glycyrrhizic acid (GA-NPs) and glycyrrhizic acid ammouniumsalt (GAS-NPs) (0.1–0.2 mM). Characterizations of the tested nanoparticles were carriedout by using dynamic light scattering which revealed that synthesized nanoparticles hadparticle sizes of less than 100 nm. In vitro studies revealed that the three tested nanoparticlesreduced the growth of A. alternata and P. digitatum. Glycyrrhizic acid nanoparticleswere the most effective in reducing the growth of the two tested pathogens followed byRA-NPs at 0.6 mM. Observations of A. alternata and P. digitatum by scanning electronmicroscopy (SEM) showed severe damage in the hyphae and deformities in the conidia dueto the effect of the tested nanoparticles. In vivo results showed that, dipping tomato fruitsas a post-harvest treatment in all of the tested nanoparticles at different concentrations,then stored at 10 ± 1°C and 90–95% relative humidity (RH) for 20 days greatly reduced thedisease severity of infected fruits with the two tested pathogens. GA-NPs at 0.2 mM significantlyreduced the development of black mold rot on tomato fruits. RA-NPs at 0.6 mM hadthe best effect in controlling P. digitatum of all naturally and artificially inoculated tomatofruits. Also, individual treatments of tomato fruits with RA-NPs, GA-NPs and GAS-NPssignificantly reduced postharvest losses of fruit since they delayed decay and maintainedfruit quality characteristics such as fruit firmness, titratable acidity and total soluble solidsduring cold storage.