Postharvest Treatments with Sulfur-Containing Food Additives to Control Major Fungal Pathogens of Stone Fruits

Abstract

The sulfur-containing salts, classified as food additives, sodium metabisulfite (SMBS), potassium metabisulfite (PMBS), aluminum sulfate (AlS), and aluminum potassium sulfate (AlPS), were evaluated for their activity against Monilinia fructicola, Rhizopus stolonifer, and Geotrichum candidum, the most economically important fungal pathogens causing postharvest disease of stone fruit. In in vitro tests with potato dextrose agar (PDA) Petri dishes amended with different concentrations of the salts (0, 10, 20, 30, 50, and 100 mM), SMBS and PMBS at all concentrations, AlS above 20 mM, and AlPS above 30 mM, completely inhibited the mycelial growth of the three fungi after incubation at 25 °C for up to 10 days. In in vivo primary screenings with artificially inoculated nectarines, aqueous solutions of the four salts reduced the incidence and severity of brown rot (BR) at concentrations of 10 and 50 mM, whereas only AlS and AlPS reduced Rhizopus rot (RR), and none of the salts was effective against sour rot (SR). Solutions at 100 mM were phytotoxic and injured the fruit peel. In small-scale trials, 1 min dip treatments at 20 °C in SMBS or PMBS at 10 mM significantly reduced the incidence and severity of BR after incubation at 20 °C for up to 8 days. Conversely, dips in AlS and AlPS reduced neither BR nor RR. Results highlight the potential of SMBS and PMBS as new nonpolluting tools for the integrated control of BR, but not RR and SR, on stone fruit.

Effectiveness of Sodium Metabisulfite against Fungal Rot of Fruit after Harvest and Assessment of the Phytotoxicity Induced in Treated Fruit

“…To our knowledge, the evaluation of salt phytotoxicity was mainly based on the qualitative visual description of the symptoms appearing after treatment of the fruit. For example, in dip treatments of stone fruit to control fungal pathogens after harvest using food additives, phytotoxicity on the fruit skin caused by the salts was assessed visually on a scale of 1 to 4, depending on the surface area covered by fungal lesions [38]. Delisle-Houde et al [39] used also visual scale of 0-4 to assess the severity of phytotoxicity of different salts on foliar surface of lettuce infected with the bacteria 'Pseudomonas cichorii' causing lettuce varnish spot.…”

Effectiveness of Several GRAS Salts against Fungal Rot of Fruit after Harvest and Assessment of the Phytotoxicity of Sodium Metabisufite in Treated Fruit

“…To our knowledge, the evaluation of salt phytotoxicity was mainly based on the qualitative visual description of the symptoms appearing after treatment of the fruit. For example, in dip treatments of stone fruit, to control fungal pathogens after harvest using food additives, phytotoxicity on the fruit skin caused by the salts was assessed visually on a scale of 1 to 4, depending on the surface area covered by fungal lesions [41]. Delisle-Houde et al [42] used a visual scale of 0-4 to assess the severity of phytotoxicity of different salts on the foliar surface of lettuce infected with the bacteria 'Pseudomonas cichorii', causing a lettuce varnish spot.…”

Postharvest VeSolution Treatment Reduced the Rot Progression and In-Transit Rotting of Pomegranate (Punica granatum L.) Fruits during Long Distance Transportation

“…In addition, numerous research has been carried on studying the antifungal activity of GRAS salts against postharvest fungal pathogens responsible for fruit rotting in Citrus [7,30], Stone fruit [14], Grapes [35],…”