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Julien Mercier, Paul Walgenbach, and Jorge I. Jiménez

The volatile-producing fungus Muscodoralbus is being developed as a biological fumigant for postharvest use, as it can kill storage pathogens and control fungal decay in various commodities. A wettable pad or sachet system made of teabag paper containing desiccated rye grain culture of M. albus was designed for the biofumigation of individual fruit containers. The fungus is reactivated before use by a brief immersion of the pad in water. This research was conducted to determine the potential of the pad system for controlling decay of table grapes in commercial cartons. Individual pads containing 24 or 86 g of grain culture (to achieve a 1:10 ratio of fumigant to box volume or a 1:100 ratio of fumigant to fruit weight, respectively) were added to Styrofoam cartons containing 8.6 kg of freshly harvested `Thompson Seedless' (TS) or `Ruby Seedless' (RS) grapes, which were then placed in cold storage at –1 to 0 °C. Control cartons exposed to SO2 were placed in a separate storage room and SO2 fumigation was performed once for TS and weekly for RS. After 8 to 9 weeks, the grapes were taken out of storage and rated for decay. In the experiment with TS, the 24-g and 86-g pads provided significant control of gray mold rot when compared to untreated cartons and were not statistically different from cartons exposed to a single SO2 fumigation. In the experiment with RS, only the 86-g pads provided significant decay control. Measurements of the three most abundant volatile compounds in empty cartons containing 10 g of the biofumigant revealed that partial coverage of holes mimicking obstruction by packed fruit achieved levels of isobutyl alcohol, 2-methyl-1-butanol, and isobutyric acid of 0.7, 1.6, and 11.2 ppb, respectively.

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Gary W. Hickman and Ed Perry

Three commercially available tree stump removal products: Dexol Stump Remover, Cooke Stump Remover & Potassium Nitrate, and Lily/Miller Stump Remover and Potassium Nitrate, as well as three nitrogen-containing fertilizers—potassium nitrate (13-0-45), ammonium nitrate (34-0-0), and ammonium sulfate (21-0-0), were evaluated for their ability to hasten decomposition of the stumps of two tree species [Eucalyptus camaldulensis Dehnh. and Paulownia tomemtosa (Thunb.) Steud.]. None of the products accelerated decay in either species after 8 weeks.

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Charles F. Forney, Roger E. Rij, Ricardo Denis-Arrue, and Joseph L. Smilanick

The potential use of vapor phase hydrogen peroxide (VPHP) to prevent decay caused by Botrytis cinerea Pers. ex Fr. in table grapes (Vitis vinifera L.) was investigated. `Thompson Seedless' and `Red Globe' grapes, inoculated with Botrytis cinerea spores, were placed in polyethylene bags and flushed for 10 minutes with VPHP generated from a 30% to 35% solution of liquid hydrogen peroxide at 40C. Immediately after treatment, bags were sealed and held at 10C. Vapor phase hydrogen peroxide significantly reduced the number of terminable Botrytis spores on grapes. The number of terminable spores on `Thompson Seedless' and `Red Globe' grapes had been reduced 81% and 62%, respectively, 24 hours following treatment. The incidence of decay on inoculated `Thompson Seedless' and `Red Globe' grapes was reduced 33% and 16%, respectively, after 8 days of storage at 10C compared with control fruit. Vapor phase hydrogen peroxide reduced the decay of noninoculated `Thompson Seedless' and `Red Globe' grapes 73% and 28%, respectively, after 12 days of storage at 10C. Treatment with VPHP did not affect grape color or soluble solids content.

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Samir Droby, Ron Porat, Lea Cohen, Batia Weiss, Boris Shapiro, Sonia Philosoph-Hadas, and Shimon Meir

Jasmonic acid (JA) and methyl jasmonate (MJ), collectively referred to as jasmonates, are naturally occurring plant growth regulators involved in various aspects of plant development and responses to biotic and abiotic stresses. In this study, we found that postharvest application of jasmonates reduced decay caused by the green mold Penicillium digitatum (Pers.: Fr.) Sacc. after either natural or artificial inoculation of grapefruit (Citrus paradisi `Marsh Seedless'). These treatments also effectively reduced chilling injury incidence after cold storage. The most effective concentration of jasmonates for reducing decay in cold-stored fruit or after artificial inoculation of wounded fruit at 24 °C was 10 μmol·L-1. Higher and lower jasmonate concentrations were less effective at both temperatures. MJ at 10 μmol·L-1 also most effectively reduced the percentage of fruit displaying chilling injury symptoms after 6 weeks of storage at 2 °C and 4 additional d at 20 °C. When tested in vitro, neither JA nor MJ had any direct antifungal effect on P. digitatum spore germination or germ tube elongation. Therefore, it is suggested that jasmonates probably reduced green mold decay in grapefruit indirectly by enhancing the natural resistance of the fruit to P. digitatum at high and low temperatures.

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Timothy M. Spann, Luis V. Pozo, Igor Kostenyuk, and Jacqueline K. Burns

further characterization of this scarring has been conducted and processors are concerned that it may reduce peel integrity and/or increase fruit decay before processing. In Florida, harvested oranges for processing are transported to the processing plant

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Andrew J. Macnish, Malkeet S. Padda, Francine Pupin, Pavlos I. Tsouvaltzis, Angelos I. Deltsidis, Charles A. Sims, Jeffrey K. Brecht, and Elizabeth J. Mitcham

( Kader, 1991 ). Fruit are also very susceptible to mechanical damage and decay ( Sommer et al., 1973 ). Botrytis cinerea and Rhizopus stolonifer , the causal agents of gray mold and rhizopus rot, respectively, are the main pathogenic fungi to infect

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U. Afek, N. Aharoni, and S. Carmeli

Since psoralens have a very weak antifungal activity in vitro, we propose that (+)marmesin, the precursor of psoralens in celery (Apium graveolens L.) is associated with celery resistance to pathogens. (+)Marmesin has at least 100 times greater antifungal activity in vitro than psoralens. After 1 month of storage at 2C, the concentration of total psoralens increased from 8 to 67 μg·g-1 fresh weight, (+)marmesin decreased from 27 to 4 μg·g-1 fresh weight, and the incidence of decay increased from 0% to 34%. However, when celery was treated with GA3before 1 month of storage at 2C, decay increased to only 7%, the concentration of psoralens increased to 31 μg·g-1 fresh weight and the concentration of (+)marmesin decreased to 13 μg·g-1 fresh weight It seems that GA3 retarded celery decay during storage by slowing down the conversion of (+)marmesin to psoralens, thereby increasing the resistance to pathogens during storage.

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Steven A. Sargent, Peter J. Stoffella, and Donald N. Maynard

Short-day onions (Allium cepa L.) grown under humid, subtropical conditions at two locations were evaluated for bulb size and yield at five harvest dates (H1 to H5) ranging from 94 to 132 days after transplanting (DAT) for `Granex 33' and from 115 to 153 DAT for `Texas Grano 1015Y'. Maximum yields were attained by H4 for both cultivars and were attributed to increased bulb size rather than differences in plant (bulb) population. Nondried, large bulbs (>7.6 cm diameter) from each harvest were trimmed and stored at 1 or 10 °C and 80% relative humidity (RH) for 2 weeks plus 2 weeks at 20 °C and 80% RH to simulate commercial storage and handling. Initial respiration rates of bulbs of both cultivars decreased >60% between H1 and H4. Bulbs also retained higher fresh weight during storage as harvest was delayed. Storage for 2 weeks at 1 °C suppressed sprouting of immature (H1) `Texas Grano 1015Y' bulbs, but not of `Granex 33' bulbs from one location. Storage at 10 °C did not suppress sprouting of either cultivar. Decay became more prevalent with delayed harvest, but `Granex 33' was more resistant to decay than was `Texas Grano 1015Y', which developed up to 40% decay after 2 weeks at 20 °C. Harvest at 115 and 132 DAT resulted in acceptable yields for `Granex 33' and `Texas Grano 1015', respectively, and satisfactory postharvest quality of nondried bulbs following 2 weeks of storage at 1 °C and 80% RH plus 2 weeks at 20 °C.

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Mark A. Ritenour*, Peter J. Stoffella, Zhenli He, and Michael S. Burton

Previous research suggests that treatment of sliced or vacuum-infiltrated tomato fruit with calcium chloride (CaCl2) solutions may reduce decay, but no work on dipping whole tomatoes has been reported. In the present experiments, `FL 47' tomato fruit were collected at the mature green or pink stage from a local packinghouse, held at 12.5 or 25.0 °C overnight, and then dipped in solutions with 0.5% to 5% CaCl2 with or without 150 ppm sodium hypochlorite. Fruit were dipped for 1 to 4 minutes at temperatures ranging from 0 to 35 °C. Mature green fruit dipped in solutions with 0.5% and 1.0% CaCl2 at 35 °C had significantly lower rates of decay following storage at 12.5 °C (90% RH) than the control (27% vs. 36% decay, respectively). These fruit were also significantly softer after 2 weeks of storage than control fruit (0.85 mm vs. 0.74 mm deformation, respectively) and appeared to be slightly more ripe. Decay in fruit dipped in 2% CaCl2 was not significantly different from the control, while fruit dipped in 3% to 5% CaCl2 developed significantly more decay than control fruit. The CaCl2 treatments had no significant effect on decay of fruit treated at the pink stage and none of the treatments at 0 °C significantly affected postharvest decay. Dips in 2% to 5% CaCl2 significantly increased tomato peel calcium content after storage. Dipping time had no significant effect on peel calcium content.

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Mario Schirra and Maurizio Mulas

Freshly harvested `Fortune' mandarins (Citrus reticulata Blanco) were dipped for 3 minutes in 25 or 52C water and then stored for 5 weeks at 2C. Then, the fruit were or were not intermittently warmed at 10C for 3 days after each 4-day storage period. All fruit then were held at 20C for 1 week to simulate retail marketing. Chilling injury was more severe in fruit dipped in 25C water and stored at 2C than in fruit dipped in 25C water and stored under intermittent warming. The hot dip treatment significantly reduced the extent of damage during storage and the subsequent 1 week of holding at 20C. The hot dip treatment reduced the incidence of fungal decay, especially during holding at 20C. Dip temperature and storage conditions slightly affected fruit physiological and quality characteristics. We conclude that prestorage hot dip treatments can be used to improve `Fortune' mandarin storing qualities. Also, this practice may be combined with intermittent warming during cold storage, and it could help limit fungicide use in postharvest treatments.