Near-Harvest Applications ofMetschnikowia fructicola, Ethanol, and Sodium Bicarbonate to Control Postharvest Diseases of Grape in Central California

Abstract

The yeast Metschnikowia fructicola, ethanol, and sodium bicarbonate (SBC), alone or in combinations, were applied to table grapes on vines 24 h before harvest to control the incidence of postharvest diseases. In four experiments, all significantly reduced the total number of decayed berries caused by Botrytis cinerea, Alternaria spp., or Aspergillus niger after storage for 30 days at 1°C followed by 2 days at 20°C. In three experiments, a mean gray mold incidence (caused by B. cinerea) of 34.2 infected berries per kilogram among untreated grape was reduced by Metschnikowia fructicola at 2 × 107 CFU/ml, ethanol at 50% (vol/vol), or SBC at 2% (wt/vol) to 12.9, 8.1, or 10.6 infected berries per kilogram, respectively. Ethanol, SBC, and SO2 generator pads were similarly effective. M. fructicola effectiveness was not improved when combined with ethanol or SBC treatments. Ethanol and yeast treatments did not harm the appearance of the grapes. M. fructicola and SBC left noticeable residues, and SBC caused some visible phytotoxicity to the rachis and berries. Ethanol applied at 50% (vol/vol) reduced epiphytic fungal and bacterial populations by about 50% compared with controls. M. fructicola populations persisted on berries during storage when applied alone or after ethanol treatments, whereas SBC reduced its population significantly.

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

“…These results are consistent with many other reports [17,27,[70][71][72]. In fact, these salts possess wide-spectrum antimicrobial properties and have been demonstrated to inhibit the growth of several fungal pathogens infecting stored fruits, vegetables, and ornamental species [17,[19][20][21][22]. To our knowledge, this is the first report on the in vitro antifungal activity of potassium salts against major fungal pathogens of tomato plants in Tunisia.…”

“…However, PB was found to be ineffective against most tomato fruit rot pathogens even though bicarbonates were reported possess wide-spectrum antimicrobial properties; their efficacy in controlling postharvest fungal phytopathogens has been widely reported [17,[20][21][22]35,37,41,80].…”

“…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].…”

Long-Term Storage Quality of Table Grapes as Influenced by Pre-Harvest Yeast Applications and Post-Harvest Use of Controlled Atmosphere

“…Harman et al (1996) showed that as few as two late-season applications of Trichoderma harzianum were nearly as effective as up to five applications throughout bloom and fruit development for the post-harvest control of gray mould of grapes. The yeast Metschnikowia fructicola Kurtzman & Droby, when applied to table grapes 24 h before harvest, reduced the total number of decayed berries in storage at 1°C for 30 days followed by 2 days at 20°C (Karabulut et al, 2003;Kurtzman & Droby, 2001). …”

The science, development, and commercialization of postharvest biocontrol products

“…Numerous reports have been published on various strategies and approaches that can be used to enhance the efficacy and reliability of postharvest biocontrol agents. These include combining biocontrol agents with use of salts and organic acids (Droby et al, 1997;Karabulut et al, 2001), glucose analogs (El Ghaouth et al, 2000), food additives Karabulut et al, 2003;Teixidó et al, 2001), and various physical treatments (Karabulut et al, 2002;Porat et al, 2002;Zhang et al, 2008). In most cases, enhanced efficacy was demonstrated using these approaches, however, each commodity-pathogen system has its own unique features and so specific protocols will need to commercially evaluated.…”