A botanical nanoemulsion against phytopathogenic fungi Colletotrichum sp. and Fusarium oxysporum: Preparation, in vitro and in vivo bioassay

Abstract

A botanical nanoemulsion (NE) comprised of cinnamaldehyde (from Cinnamomum cassia oil) and annonaceous acetogenin (AAs) (from Annona squamocin seeds extract) was fabricated using sonication. The nanoemulsion was tested for their in vitro and in vivo antifungal activity against Colletotrichum sp. and Fusarium oxysporum the disease-causal agents in fruit and vegetable crops. The best average of nanoemulsion hydrodynamic diameter was 245.3 nm, and the polydispersity index (PI) was 0.499 based on DLS measurement. Zeta potential of the nanoemulsion was determined to be −44.2 mV, indicating the stability of the droplets. In vitro antifungal bioassay of the nanoemulsion showed the best inhibition against Colletotrichum sp. by 53.9 % when tested at a dilution rate of 1:100 (v/v). For F. oxysporum, the nanomaterial also inhibited mycelial growth by 91.6 % at the same dilution rate. When tested at dilution rates of 1:200 and 1:400 (v/v), the nanoemulsions caused moderate and weak inhibitions from 30.9 % to 52.8 % for all fungi. In vivo experiment, the nano-emulsion at 1:200 (v/v) dilution demonstrated an antifungal efficacy of 57.1 % (after 4 days) and 49.6 % (after 7 days) of testing. Besides, the mechanism of action has also been elucidated through molecular interaction models between the main compounds with eburicol 14α-demethylase. Our research indicates that botanical nanoemulsion containing cinnamon oil and AAs have a remarkable potential to suppress phytopathogenic fungi and prevent the spread of fungal diseases in tropical fruits and vegetables such as tomato and other crops of Solanaceae family.