Postharvest Application of Organic and Inorganic Salts for Suppression of Silver Scurf on Potato Tubers

Abstract

Seven organic and inorganic salts were tested for suppression of silver scurf, a postharvest disease of potato tubers caused by Helminthosporium solani. Potassium sorbate, calcium propionate, sodium carbonate, sodium bicarbonate, potassium carbonate, potassium bicarbonate, and ammonium bicarbonate were added to V8 agar at concentrations of 0.06–0.2 M. Radial growth of H. solani was significantly reduced (P < 0.05) by all salts at all concentrations. All salts except sodium bicarbonate and potassium bicarbonate were fungicidal at 0.2 M. Effects of postharvest salt treatments on disease severity and sporulation of H. solani on inoculated and naturally infected potato tubers were evaluated in separate experiments. Greenhouse-grown tubers were inoculated with H. solani spore suspensions (2 × 105 spores/ml), incubated for 5 days, dipped into 0.2 M solutions of each of the salts, and incubated in a moist chamber at 22–24°C for 6 weeks. All salt treatments prevented lesion development and sporulation of H. solani and differed significantly (P < 0.05) from the control. Postharvest applications of test compounds (0.2M) also significantly (P < 0.05) reduced disease severity and H. solani sporulation on naturally infected, field-grown tubers after 15 weeks of storage at 10°C. Salt treatments did not differ in disease or pathogen suppression. These relatively nontoxic organic and inorganic salts have potential as postharvest applications for control of silver scurf.

Comparative Efficacy of Potassium Salts Against Soil-borne and Air-borne Fungi and Their Ability to Suppress Tomato Wilt and Fruit Rots

“…For each potassium salt tested, the exact concentration required to inhibit fungal growth differed somewhat between tomato pathogens. These results are consistent with other studies demonstrating that suppression of microbial strains varies in response to different organic and inorganic salts Olivier et al and Fagundes et al, [17,35] show that the percentage of fungal inhibition in amended PDA medium was dependent on concentration used, and that the most significant decrease in mycelial growth was obtained with the highest concentration of salt tested. In fact, the effectiveness of potassium salts in controlling various plant pathogens have been previously reported [18,[36][37][38][39][40].…”

“…In the same sense, Mecteau et al, [18] showed that the organic anions sorbate completely inhibit mycelial growth of F. sambucinum, the causal agent of potato dry rot, at 0.2 M, while for spore germination the ED50 was 0.56 mM. Sorbate has also shown toxicity on mycelium of Helminthosporium solani, an important potato pathogen and always ranked first in efficacy, since it was fungicidal at concentrations as low as 0.05 M [17]. Sorbate has also shown toxicity on mycelium of Helminthosporium solani, an important potato pathogen and always ranked first in terms of efficacy [17].…”

“…Potassium bicarbonates and carbonates have been demonstrated to inhibit the growth of several fungal pathogens infecting vegetables and ornamental crops at the post-harvest phase [17,[20][21][22]. In the same manner, foliage spays of sodium or potassium bicarbonates led to decreased powdery mildew severity (Leveillula taurica) in pepper plants [23].…”

“…attention to search for alternative methods for tomato diseases' management. An interesting alternative to chemical control involves the use of the antimicrobial properties of some organic and inorganic salts, generally used in food processing and preservation, to control plant diseases [16][17][18].…”

“…Importantly, these salts have a broad spectrum of antimicrobial activity with low mammalian toxicity, possess biocompatibility [16,17], and are generally recognized as safe (GRAS). Thus, they are widely exploited in food industry as preservatives, pH regulators and antimicrobial agents [17].…”