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- Author or Editor: E. Chalutz x
- HortScience x
Abstract
An inexpensive method for accurate control and measurement of fresh air introduction into experimental storage rooms is described.
Abstract
We discuss criteria for the design of cold storage facilities for use in research. Factors considered are: determination of the desired accuracy of temperature and relative humidity control, methods of air circulation and fresh air introduction.
Abstract
With the expected ban on ethylene dibromide fumigation, cold exposure remains the only quarantine treatment for citrus fruit against the Mediterranean fruit fly. Following a cold treatment, ‘Marsh’ grapefruit (Citrus paradisi Macf.) developed chilling injury (Cl), mostly in the form of slight peel pitting on 3% to 10% of the fruit depending on the season and on other factors. There was no difference in the incidence of Cl between fruit treated at 0°C for 10 days or at 2.2° for 16 days as regulations require. The cold treatment also enhanced decay development during long-term storage of the fruit at 11°. Mold rots developed on Cl peel pitting, and their incidence increased from 1.7% to 3.5% during a storage period of 12 weeks. The presence of the fungicide Thiabendazole (TBZ) in the wax coating of the fruit reduced the incidence of Cl by more than 50%. Delayed cooling, i.e., keeping the freshly harvested packed fruit for 6 days at 17°C prior to initiation of cold treatment, reduced the incidence of Cl by the same extent. By combining a TBZ treatment with delayed cooling, the susceptibility of grapefruit to Cl can be reduced, and cold treatment can be practiced with a low risk of Cl and subsequent decay development.
Abstract
Incorporation of thiabendazole (TBZ) in the wax coating applied to grapefruit significantly reduced the amount of low temp pitting which developed during prolonged storage at 8 and 12°C.
Jewel sweetpotato storage roots previously treated with ultraviolet (UV–C) light and then stored for 30 days before artificial inoculation with Fusarium solani showed increased resistance to Fusarium root rot; as indicated by reduced lesion size, the rate of decay development of rotted tissues. There was a hormetic relationship between the incidence of Fusarium root rot and UV–C doses. The optimum dose of UV which reduced Fusarium root rot was 3.6× 104 ergs/mm2. Exposure of sweetpotato to UV–C doses promoted phenylalanine ammonia–lyase (PAL)4 production with the maximum PAL activity occurring at 3.6×104 ergs/mm2. Crude extracts from UV–C treated sweetpotatoes reduced germination, germ tube elongation and growth of F. solani when compared to untreated extracts.
Low doses of ultraviolet light (254nm UV–C) irradiation reduced postharvest rots of pome, stone and citrus fruits. Brown rot (Monilinia fructicola) of `Elberta' and `Loring' peaches was significantly reduced by UV–C. Alternaria rot (Alternaria spp.) and bitter rot (Colletotrichum spp.) the principal storage rots of `Golden Delicious apples showed significant reduction following UV–C treatment. Further application of UV–C was effective in controlling green mold rot (Penicillium digitatum) of `Dancy' Tangerines and `Marsh Seedless' grapefruits, stem end rot (Alternaria citri), as well as sour rot (Geotrichum candidum) of `Dancy' tangerines after irradiation.
Applying low doses of ultraviolet light (254 nm, W-C) reduces the incidence of brown rot of (Monilinia fructicola) peaches, green mold (Penicillium digitatum) of tangerines, and Rhizopus soft rot (Rhizopus stolonifer) of tomatoes and sweetpotatoes resulting from field infection and artificial inoculation. In most studies, applying postharvest fungicide (PF) was better than W-C treatment. In this study, the effectiveness of combining a biocontrol agent, Debaryomyces hansenii (BC), with low UV-C dose for postharvest disease control was investigated. When these commodities were treated with BC 3 days after W-C treatment, the reduction of storage rots was more effective than when UV-C was used alone. For example, the percent brown rot infection of artificially inoculated Elberta peaches 36 hours after inoculation of the nontreated control, peaches treated with UV-C, BC, W-C + BC, and benlate were 100%, 55%, 67%, 12%, and 12%, respectively. The efficacy of W-C + BC was similar to when PF was used alone, indicating that an integration of UV-C treatment and BC can reduce storage rot to the levels of commercial PF treatment.
Low hormetic doses of ultraviolet light (UV-C) stress on exposed peaches (Prunus persica). reduced brown rot resulting from field and artificial inoculation from Monilinia fructicola. To test the hypothesis that UV-C induced resistance through host responses the following tests involving biochemical changes (phenlyalanine ammonia-lyase activity (PAL) and ethylene production (EP)), bioassay of antifungal activity of tissue extracts to the fungus, and latent infection of rot free peaches previously treated with and without UV-C were determined. Exposure of peaches to UV-C dose of 7.5×104 ergs/mm2 promoted an increase in PAL and EP compared to the control. As the PAL activity increased, percent storage rots decreased. Antifungal activity to the fungal conidia in UV-C treated peach extract showed that the percent conidia germination was reduced 3 folds. Preharvest infection of brown rot which indicated latent infection was significantly reduced. To test for the germicidal effect of UV-C on M. fructicola on the surface of peaches, an artificial epiphytic population of the fungus was deposited on the peaches. A negative relationship between UV-C dose of 1.3 to 40×104 ergs /mm2, colony forming units and number of decaying brown rot lesions were found.
The application of low hormetic low-dose ultraviolet light (WV-C, 254 nm) on fruits and vegetables to stimulate beneficial responses is a new method for controlling storage rots and extending the shelf-life of fruits and vegetables. The present study was aimed at treating tomatoes (lycopersicon esculentum) with different UV-C dosages (1.3 to 40 KJ/m2) to induce resistance to black mold (Alternaria alternata), gray mold (Boytris cinerea), and Rhizopus soft rot (Rhizopus stolonifer). Thesediseases were effectively reduced when tomatoes were artificially inoculated following UV-C irradiation UV-C treated tomatoes were firmer in texture and less red in color than the control tomatoes, indicating a delay in ripening. Slower ripening and resistsace to storage rots of tomatoes are probably related. The positive effect of UVC on tomatoes decreased as treatments were performed at stages of increased ripeness.