The effect of silver and other metal ions on the in vitro growth of root‐rotting Phytophthora and other fungal species

Abstract

A range of metal ions and the oxoanion W04" were toxic to zoospores of Phytophthora nicotianae parasitica in the order: Ag+ >> Cu++ > W04?-> Ni+ > Co++ > Zn'. The LDS0 for Ag', 0.11 ,UM (11.4 ppb), compared with 1.84 ,UM (1 17 ppb) for Cu". Silver was similarly toxic to a range of pathogens including Pythium aphanidermatum, Thielaviopsis basicola and Fusarium oxysporum f.spp. Most zoospores of Phytophthora spp. were killed by Ag+ in the range 46 -460 nM (5 -50 ppb), bursting at the higher concentrations. A small sub-population of most propagules exhibited greater tolerance to silver than the whole. In 0.93 ,UM (100 ppb) Ag+ 1.4% of P. nicotianae parasitica zoospores survived but were all killed at 500 ppb. A population of P. cryptogea (1.9%) surviving 0.47 ,UM (50 ppb) were killed at 0.93 PM (100 ppb). Zoospore cysts and germlings showed the same sensitivity to silver. Oospores were mostly killed over the range 0.23 -0.93 ,UM (25 -100 ppb) Ag', some surviving up to the lethal concentration of 9.26 ,UM (1000 ppb). Mycelium of P. cryptogea was generally less sensitive, with some growth occurring at 9.26 PM (100 ppb).Zoosporangiogenesis was unaffected over the range 0.47 -4.65 ,UM (50 -500 ppb). Toxicity increased with increased pH over the range 5.0 -6.5.Ionic silver was lost from solution during a microscope slide bioassay by binding to the glass surface. In the presence of chloride ions, colloidal AgCl formed which was equally toxic to P. cryptogea. Silver and AgCl were further lost from solution by colloidal agglomeration -Ostwald ripeningand by AgCl adsorption to glass. Silver, < 90 nM (10 ppb) Ag' as AgN03 and particles of silver chloride were both strongly attractive to zoospores of P. cryptogea. Spores burst or failed to germinate on entering lethal concentrations. The results are discussed in the context of the use of silver salts to control Phytophthora rootrot pathogens and the importance of ion availability in in oitro toxicity assays. Horsfall J C. 1956. Principles of firtigicidal action. Waltham. Massachusetts: Chronica Botanica Co. Huot T. Bouchardat G. 1899. Sur I'emploi des sels mercuriques et du nitrate d'argent en viticulture. Jain $1 li. 1977. Hundbook of e x y m e irihibitors. UK: Wiley. Kennedy B W. Erwin D C. 1961. Some factors influencing sporangium formation of a Phytophthora species isolated from lucerne in certain salt solutions. Transactions of the British Mycological Society Kennedy R, Pegs G F. 1990. Phytophthora cryptogen root rot of tomato in rockwool nutrient culture. 11. Effect of root zone temperature on infection sporulation and symptom development. Annuls of Applied Biology 117537-55 1. Khew K L. Zentmyer G A. 1973. Chemotactic response of zoospores of five species of Phvtophtliora. Krause G A. 1929. Neice Wege sirr Wussersterilisierirrig. Munich: J F Bergmann. Menyonga J M, Tsao P H. 1966. Production of zoospore suspensions of Pliyoplitlioru pnrasiticir. Miller L P, McCallan S E A. 1957. Toxic action of metal ions to fungus spores. Agricitltitral and Food Miller L P, McCallan S ...

Effects of Inorganic Elements on the In-vitro Growth of Pythium aphanidermatum (Edson) Fitzp.

“…Silver reduced germination when it was applied at 0.1 mg/L and stopped it at 0.5 mg/L. Slade and Pegg 13) reported that Ag could completely inhibit the germination of zoospores of P. aphanidermatum at concentrations above 0.1 mg/L. The difference between our result and their result could have been the fact that Ag can bind with other elements and substrates, which mitigates the inhibitory effects of Ag.…”

“…Group C includes miscellaneous elements (iodine, F, Li, Ba and Ag). Some of these were reported to have adverse effects on pathogens 11,13) .…”

Fungicidal and antibacterial activity of the hydrogel compositions with silver

“…Such causative agents as late blight and black leg of potato were used for the laboratory experiments. Unlike previous studies [2,[10][11][12][13][14], this research involves the assessment of non-water solutions such as gel compositions of the PPA with colloidal and ionic form of silver nitrate (AgNO3). These compositions improve the stability of the nanoparticles, and in the practical use guarantee fixation of PPA in the rhizosphere and its protection from leaching.…”

“…Two main objectives of the research are as follows: 1) to assess the antifungal and antibacterial effects of gel compositions with silver in order to determine the range of PPA doses for subsequent trials under field conditions; 2) to compare the effectiveness of different forms of silver and different types of hydrogels. Based on the previous studies [2,[10][11][12][13][14][15][16], the dose of silver should not exceed 100 ppm, which is economically sufficient considering an average price of silver 15-30$ per Trinity oz.. This study compared the efficiency of the two agents, as well as several types of hydrogels: a convenient "Aquasorb" based on polyacrylamide and new hydrogels produced at the Ural Chemicals Factory by our proprietary technology with the filling of the polymer matrix.…”

“…Two types of growth inhibitors were used, colloidal silver and ionic silver (chemically pure AgNO3) in the composition with three types of hydrogels (hydrophilic agent Aquasorb (France) based on polyacrylamide, acrylic gel VUM-0 with hydrophilic filler in the form of waste biocatalytic production of polyacrylamide and acrylic gel PM-1 with amphiphilic filler in the form of dispersed peat). The latter is an experimental product of the Ural Chemicals Factory from patent-pending technology [4][5][6][7][8][9][10][11][12][13][14][15][16][17]. The colloidal silver is an experimental product "Zeroxxe" of AgroChimProm GC (http://tdahp.ru/en/,) that contains silver nanoparticles with a size of 10-70 nm superficially modified with environmentally safe biodegradable amphiphilic surfactant (tallow amphopolycarboxyglycinate-stabilizer [18].…”