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Fanjaniaina Razafimbelo, Jacqueline F. Nock, and Chris B. Watkins

The `Empire' apple cultivar is susceptible to external CO2 injury, a physiological disorder that is expressed as tan-colored, smooth, watersoaked areas that become irregularly shaped, rough, depressed, and wrinkled. 1-Methylcyclopropene (1-MCP) may increase susceptibility of fruit to external CO2 injury during controlled atmosphere (CA) storage. We have investigated the effects of 1-MCP on external CO2 injury of `Empire' apple using several approaches. 1) Fruit were treated with 1%, 2.5%, and 5% CO2 during storage. Higher injury levels were associated with exposure to higher CO2 concentrations. 2) Fruit were exposed to 2.5% or 5% CO2 for 3-week periods throughout storage, otherwise being kept at 1% CO2. Most injury occurred in fruit treated with elevated CO2 during the first 3 weeks of storage, and 1-MCP did not extend the period of susceptibility to injury. 3) Exposure of fruit to CA with 5% CO2 after harvest was delayed for up to 14 days. Susceptibility to injury remained high during the delay in 1-MCP-treated fruit in contrast to untreated fruit. 4) Fruit were treated with 250, 500, and 1000 μL·L-1 diphenylamine (DPA), an antioxidant applied for control of superficial scald that is known to prevent susceptibility of fruit to CO2 injury at 1000 μL·L-1. The DPA eliminated injury in 1-MCP treated fruit, even at 250 μL·L-1. Our data show that 1-MCP increases susceptibility of `Empire' apples to external CO2 injury and extra care is therefore required to avoid fruit losses. Nonchemical means may reduce losses, but only DPA application has been shown to eliminate risk of injury.

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C.B. Watkins, K.J. Silsby, and M.C. Goffinet

1 Associate Professor. 2 Regional Extension Specialist. 3 Current address: Sun Orchard Fruit Co., Inc., 2087 Transit Rd., Box 40, Burt, NY 14028. 4 Research Associate. Department of Fruit and Vegetable Science paper number No. 63. This

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Thanaa M. Ezz, Mark A. Ritenour, and Jeffrey K. Brecht

1 Current address: Faculty of Agriculture—Saba Bacha, Alexandria Univ., POB 21531, Alexandria, Egypt. 2 Indian River Research and Education Center, Univ. of Florida, 2199 S. Rock Rd., Ft. Pierce, FL 34945-3138; mritenour@ifas.ufl.edu . 3 To whom

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R. Romero-Aranda and J.P. Syvertsen

The penetration of foliar-applied urea and salt solutions into citrus leaves was investigated using `Duncan' grapefruit and `Valencia' orange seedlings in a greenhouse, and 8-year-old `Ruby Red' grapefruit trees in field tests during the summer and fall. Net gas exchange rates, Cl, nitrogen, and chlorophyll concentrations of singles leaves were measured during or after the period of foliar applications. Foliar-applied salt treatments increased leaf Cl, and visible burn symptoms were observed when Cl levels reached ≈0.4% of leaf dry weight. After 11 weeks, green areas from salt-treated leaves had similar rates of net CO2 assimilation as control plants. Leaf nitrogen and total chlorophyll increased with repeated sprays. Urea sprayed at 15% caused foliar burn symptoms after two to three applications and increased the amount of leaf abscission. Urea sprayed at 6% increased CO2 assimilation rate ≈50% after three foliar applications in 3 weeks. Nitrogen content and net CO2 assimilation of urea and urea + salt leaves were similar.

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Samuel S. Liu and Yong-Biao Liu

aphid resulted in significant injuries to both romaine and head lettuce in the form of brown stains identical to CO 2 injuries ( Lipton et al., 1972 ; Liu, 2012 ). Because cylindered phosphine is free of ammonia, it is possible that factors other than

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C.B. Watkins and F.W. Liu

temperature, high partial pressures of CO 2 (pCO 2 ) as well as factors such as mineral nutrition ( Meheriuk et al., 1994 ; Snowden, 1990 ). Another disorder of ‘Empire’ apples that is important to the industry is external CO 2 injury ( Watkins et al., 1997

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Rachel S. Leisso, Ines Hanrahan, James P. Mattheis, and David R. Rudell

rates may affect symptom development. Previous research also reveals increases in ethanol and fermentative odors concurrent with soggy breakdown development ( Smock, 1977 ). Internal CO 2 injury of ‘Honeycrisp’ apple fruit has not been exhaustively

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Yuji Nakata and Hidemi Izumi

by strawberry fruit, thereby making them susceptible to CO 2 injury ( Watkins, 2000 ). Ke et al. (1991) reported that CO 2 levels of >20% caused injury with a change in skin and/or flesh color from red to dark–blue-red in strawberry fruit after 10

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Carolina Contreras, Nihad Alsmairat, and Randy Beaudry

. Many fruit cultivars develop physiological disorders in response to exposure to the low O 2 and elevated CO 2 partial pressures of CA storage. CA storage injury (CA injury) can be caused by low O 2 , elevated CO 2 , or a combination of both ( Pierson

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Leonardo Lombardini, Astrid Volder, Monte L. Nesbitt, and Donita L. Cartmill

selected based on a visual estimate to represent the entire range of actual injury in the data set. Measurements were taken on the non-injured portion of the leaflet lamina, adjacent to the injured area. Chamber air CO 2 concentration was set at 390 μL