The efficacy of Salicylic Acid and Glycyrrhizic Acid Ammonium Salt in the Bulk and Nanoforms on Rhizoctonia solani Damping off and Root Rot Diseases in Soybean Plants

Soybean is a vital crop in Egypt, recognized for their high oil and protein content. Although damping-off and root-rot diseases pose significant threats to soybean production and quality, El-Giza-R.s6 (NCBI accession number PX694340) exhibited the highest aggressiveness among the Rhizoctonia solani isolates in vivo. Salicylic acid (SA) and glycyrrhizic acid ammonium salt (GAS), in both nanoparticles (NPs) and bulk form, significantly inhibited the linear growth of R. solani in PDA medium at 0.5, 1.0, 1.5, and 3.0 ml/L concentrations, particularly by increasing SA and GAS concentrations to 3 ml/L in nanoparticles than in their bulk forms. GAS and SA, both in bulk form and as NPS at concentrations of 1.0, 1.5 and 3 ml/L, along with the fungicide Topsin-M 70®, significantly reduced R. solani damping-off and root-rot diseases, while also increasing plant survival in greenhouse and field trials. Among all treatments, Topsin-M 70® was the most effective, followed by SA-NPs and GAS-NPs at a concentration of 3 ml/L. Furthermore, soybean root cross-sections examined under a light microscope showed that these treatments prevented the plants from harmful anatomical changes caused by the pathogenic fungus in the epidermis, cortex, and vascular cylinder structure due to artificial infestation in vivo. Additionally, these treatments notably enhanced the enzyme activity of β-1,3-glucanase, polyphenol oxidase, and catalase in soybean leaves compared to both infested and uninfested controls. During the 2024 and 2025 growing seasons in El-Menuofia Governorate, SA-NPs, Topsin-M 70®, and GAS-NPs were the most effective treatments, significantly improving soybean yield and its components.