Impact of glycyrrhizic acid ammonium salt nanoparticles and salicylic acid nanoparticles on Ralstonia solanacearum suppression and soil microbial biodiversity

Bacterial wilt, also known as potato brown rot, caused by Ralstonia solanacearum, is a quarantine disease in several areas worldwide that can significantly decrease crop yields. The study aimed to evaluate the effects of glycyrrhizic acid ammonium salt nanoparticles (GAS-NPs) and salicylic acid nanoparticles (SA-NPs) on R. solanacearum growth and bacterial wilt development. Four nanoparticle concentrations (0.05, 0.1, 0.15, and 0.3 ml/100 ml) were tested in vitro; only 0.1 ml/100 ml and 0.3 ml/100 ml were selected for a greenhouse experiment. GAS-NPs caused a change in the pathogen to the avirulent form at 0.3 ml/100 ml. Tomato seedlings, as indicators, were employed to test the effect of the different nanoparticles on disease development under greenhouse conditions. The highest suppressive potential was recorded for GAS-NPs at 0.3 ml/100 ml, followed by SA-NPs at 0.3 ml/100 ml. The disease was suppressed by 100 % and 92 %, respectively, indicating the potential of GAS-NPs and SA-NPs as effective treatments. Metagenomics analysis was employed to study the impact of the high concentration of the two nanomaterials on tomato rhizosphere bacterial biodiversity. SA-NPs caused a clear shift in bacterial biodiversity with a significant decrease in alpha diversity. A general increase in the abundance of Firmicutes and a decrease in the abundance of Acidobacteriota, Chloroflexi, and Thermomicrobiales compared to the untreated control was recorded. GAS-NPs increased the abundance of Micrococcaceae. GAS-NPs are to be evaluated under field conditions in the long term to further confirm their direct effect on pathogen virulence and low impact on soil biodiversity.