ABSTRACT
Antifungal efficacy of Aloe vera-mediated silver nanoparticles in different concentrations and application methods against Fusarium oxysporum in Cucurbita pepo

Eman Selim1*, Esraa Saeed1, Yasser Selem2, Mayasar I. Al-zaban3, Eman Fayad4, Asim Ahmed S. Alsenani4, Hana Alsufyani4, and Hanan Abdallah1*
 
Fusarium wilt seriously threatens Cucurbita pepo L. production worldwide. Plant-based nanotechnology antifungals offer a promising and eco-friendly control strategy. This study investigated the antifungal efficacy of Aloe vera (L.) Burm. f.-mediated Ag nanoparticles (Ag-NPs) against Fusarium oxysporum. Biogenic Ag-NPs were synthesized using A. vera leaf extract with an average crystallite size of 15.22 nm and a surface plasmon resonance peak at 413 nm. In vitro, Ag-NPs at 2.5, 5, 10, and 15 mg L¹ generated dose-dependent inhibition zones (0.5-2.0 cm). The concentration 15 mg L-1 produced the largest inhibition zone (2.0 cm) and the greatest reduction in colony diameter. In vivo greenhouse trial, Ag-NPs were tested at 2.5, 5, 10, and 15 mg L¹ by foliar spray or soil drench (pre-planting) on Fusarium-inoculated plants vs. uninoculated and inoculated controls. Fusarium infection severely reduced plant growth (47%-155%), photosynthetic pigments (47%-58%), and mineral elements (30%-80%) compared to the uninoculated control (T1). However, Ag-NPs applications displayed strong antifungal agents and plant biostimulants. In particular, 15 mg L¹ foliar Ag-NPs (T5) displayed the significant improvement in leaf number (43.1%), shoot length (42.9%), biomass (68.0%-154.5%), chlorophyll a and b (112.5% and 100%), phenols (40.0%), sugars (14%), and minerals Ca/Mg/Na/K (42.9%, 150.0%, 150.0%, and 42.9%) compared to the inoculated control. Moreover, increasing Ag-NPs concentration mitigated oxidative stress in infected plants by enhancing activities of catalase, superoxide dismutase, polyphenol oxidase, and peroxidase. Multivariate analyses (principal component analysis and heatmap) showed that high-dose Ag-NPs were associated with improved growth and mineral traits, antioxidant and osmoprotective metabolites.
Key words: Antifungal activity, antioxidant enzymes, cucurbit wilt, green synthesis, phytochemicals, silver nanoparticles.
1Zagazig University, Faculty of Science, Plant Physiology Department, Zagazig 44511, Egypt.
2Zagazig University, Faculty of Specific Education, Organic Chemistry Department, Zagazig 44511, Egypt.
3Princess Nourah bint Abdulrahman University, College of Science, Department of Biology, Riyadh 11671, Saudi Arabia.
4Taif University, College of Sciences, Department of Biotechnology, Taif 21944, Saudi Arabia.
*Corresponding author (eman8_extra8@yahoo.com; h.abdallah@zu.edu.eg)