Effect of silver nanochitosan on control of seed-borne pathogens and maintaining seed quality of wheat

Abstract

Seeds, considered as the foundation of agriculture, are invaded by a broad spectrum of seed-borne pathogens. The current study aimed to control seed-borne fungal pathogens of wheat, Aspergillus flavus and A. niger, by using Ag+ nanochitosan (Ag-NC) for nano-priming of seeds and enhancing seed quality. Nanochitosan (NC) and Ag-NC were synthesized using the gelation method and characterized by UV–vis spectrophotometry, FESEM, EDXS, and HRTEM. NC and Ag-NC showed irregular surface topography with an average particle size of 275 and 325 nm, respectively. Antifungal activity of both the nanoparticles at 0.1, 0.2, 0.3, 0.4, and 0.5 mg/mL revealed that Ag-NC at 0.5 mg/mL has completely terminated the mycelial growth of both pathogens. Malonaldehyde content increased to 77.77% in A. flavus and 82.66% in A. niger when exposed to 0.5 mg/mL Ag-NC. High-intensity fluorescence due to oxidative stress was observed in Ag-NC-treated pathogens. Ultra-structural changes in Ag-NC treated pathogenic spores under SEM displayed pronounced membrane damages. Wheat seeds were nano-primed with NC and Ag-NC at 0.5 mg/mL, and fungal load was examined to evaluate the mitigation of pathogenic stress and its effect on seedling growth promotion activity. Ag-NC priming reduced the fungal load and allowed successful seed germination. Ag-NC priming increased the albumin, gliadin, gluten, and glutenin content along with total phenol, reducing sugar and starch levels. Ag-NC priming increased the overall protein levels traced through SDS-PAGE. Seed priming with Ag-NC promotes seed germination, mean germination time, stress tolerance index, vigour, etc. NC and Ag-NC at 0.5 mg/mL showed no cytotoxic effect on the Human Embryonic Kidney (HEK293) cell line that ensures the nanoparticles are non-toxic. Thus, the synthesized nanoparticles exhibit a dual role in antifungal activity and plant growth promotion.