Effect of Nanoscale Silicate Platelets on Azoxystrobin-resistant Isolates of Botrytis cinerea from Strawberry In Vitro and In Vivo

The inhibitory effect of nanoscale silicate platelets modified with different surfactants, i.e., NSS1450 and NSS3150 was evaluated for spore germination and mycelial growth of azoxystrobin-resistant (AR) and -sensitive (AS) Botrytis cinerea isolates from strawberry. The treatments with NSS1450 at the concentration of more than 50 mg/L significantly reduced spore germination by 99.2-100.0% for AR isolates and by 100.0% for AS isolates. In contrast, NSS3150 failed to show an inhibition for the spore germination of AR B. cinerea isolates. In another test, NSS1450 at concentrations higher than 500 mg/L could reduce mycelial growth by 60.2-100.0% and 93.8- 100.0% for AR and AS isolates, respectively, while NSS3150 showed similar inhibition on the spore germination. Further, NSS1450 at the concentrations between 500 to 1000 mg/L and accompanied with a fungicide, azoxystrobin, demonstrated high inhibitory rate 93.8 to 100.0% inhibition) in AR and AS isolates of B. cinerea. Under scanning electron microscope, the NSS1450 at the concentration of 1000 mg/L affected the morphologies of spores and mycelia in shrinking. The disease severity on strawberry leaves was 8.3% after 13 days incubation when treated with NSS1450 at 24 h after the pathogen inoculation. Moreover, spraying the mixture solution of 100 mg/L NSS1450 and 100 mg a.i./L azoxystrobin at 24 h after or before pathogen inoculation showed significantly efficacy compared with inoculation pathogen only. The results indicated that the silicate nanoplatelets after modification by a proper surfactant or NSS1450 had the potentials for treating gray mold disease although further studies are still needed under greenhouse and field conditions.