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Jiregna Gindaba and Stephanie J.E. Wand

We investigated the effects of evaporative cooling (EC), kaolin particle film (KP) and 20% shade net (SN) on the control of sunburn, fruit temperature amelioration and fruit quality of `Cripps' Pink' and `Royal Gala' apples [Malus domestica Borkh.] under orchard conditions during the 2003–04 season in Stellenbosch, South Africa. On days with maximum air temperatures of 34 to 37 °C, SN fruit were 5.4 to 9.7 °C cooler, EC fruit were 3.1 to 5.8 °C cooler and KP fruit were 1.5 to 6.4 °C cooler compared to the control (nontreated, CO) fruit. SN was effective in reducing fruit temperature from mid-morning until midafternoon; KP was most effective during late morning and early afternoon but not at midday; EC was effective from late morning on days when EC was activated. SN, followed by KP, was the most effective technique for controlling sunburn in fruit of both cultivars, with EC being less effective. The different technologies reduced fruit blush color compared to the CO treatment, with SN showing the most reduction and EC the least. EC increased fruit mass compared to all other treatments in `Royal Gala', and also increased fruit diameter and mass compared to CO in `Cripps' Pink'. We conclude that under the high radiation levels experienced in South African apple production areas, technologies which reduce irradiance as well as fruit temperature (KP, SN) are more effective in reducing sunburn than those which only reduce fruit temperature (EC). However, radiation-reducing technologies are potentially detrimental to color development on blushed apples.

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Brian Makeredza, Michael Schmeisser, Elmi Lötze, and Willem J. Steyn

The external appearance of fruit is a crucial factor in consumer preference ( Steyn, 2012 ). Sunburn, a disorder of the fruit peel caused by high temperature in combination with high irradiance ( Glenn et al., 2002 ; Schrader et al., 2003

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Brian Makeredza, Helen Marais, Michael Schmeisser, Elmi Lötze, and Willem J. Steyn

The Mediterranean-type climate apple production areas of the Western Cape of South Africa are subject to high irradiation and high summer temperatures. These environmental conditions are conducive to the development of sunburn ( Schrader et al

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Larry E. Schrader, Jianguang Zhang, Jianshe Sun, Jizhong Xu, Don C. Elfving, and Cindy Kahn

Sunburn of apples is a physiological disorder caused by heat and/or light stress ( Felicetti and Schrader, 2008a ; Schrader et al., 2001 , 2003a , 2004 ). Sunburn markedly increases cullage and results in large economic losses to growers

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David A. Felicetti and Larry E. Schrader

Apple sunburn is a serious problem in many parts of the world where apples are grown in the presence of high solar irradiance and high temperature. Three types of apple sunburn have been characterized in the author's laboratory at Washington State

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Larry E. Schrader

Sunburn, a result of high solar radiation that overwhelms natural protection systems, causes large economic losses in fruits and vegetables grown in arid and semiarid regions of the world. Sunburn damage to apples ( Malus domestica Borkh.) has been

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Giverson Mupambi, Nadia A. Valverdi, Hector Camargo-Alvarez, Michelle Reid, Lee Kalcsits, Tory Schmidt, Felipe Castillo, and Jonathan Toye

Protective netting is increasingly being used by tree fruit growers worldwide to reduce fruit sunburn and protect trees from hail damage ( Mditshwa et al., 2019 ; Mupambi et al., 2018a ). Sunburn is a physiological disorder that causes cosmetic

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Jacques R. Fouché, Stephanie C. Roberts, Stephanie J.E. Midgley, and Willem J. Steyn

red blush, sunburn blemishes, and whitening of the peel. Fruit with sunburn or red blush are downgraded to Class 3 and will not pass for export. Although older GS orchards are being replaced with more profitable cultivars, GS will remain an important

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Triston Hooks, Genhua Niu, Joe Masabni, Youping Sun, and Girisha Ganjegunte

needed to gain a better understanding of the genetic diversity that exists among pomegranate varieties. Other production issues of pomegranate are fruit rot and sunburn. Fruit rot is often caused by fungal pathogens, such as Coniella granati ( Levy et

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Pinghai Ding* and Leslie H. Fuchigami

Sunburn can be caused either by heat stress or by UV-B radiation. Under natural conditions fruit sunburn is usually caused by the combination of both heat stress and UV-B radiation. To evaluate the use of reflectance spectroscopy in early detection of fruit sunburn, 5-year-old `Fuji' apple bearing trees growing in pot-in-pot system at the Lewis-Brown Horticulture Farm of Oregon State Univ. were used in the experiment. Fruit sunburn was monitored either under natural conditions or treated with UV-B, heat or both under controlled conditions after detached from the tree. Under natural conditions, the sun-exposed side of Fuji fruit has much higher anthocyanins than the shaded side. The increase in anthocyanins at the sun-exposed side is to protect the fruit from sunburn. When the temperature higher than 40 °C the sunburn symptom initiated first by change the color of the sun-exposed side from red to tan, then to yellow patches, and finally turn to brown and dark brown patches. The peel pigments analysis results indicated that anthocyanins decreased earlier than chlorophyll in the symptom development. The results of detached fruit exposure to 30,000μW/cm2 UV-B lights or to 40 °C at control conditions for 2, 4, 6, 8, 10, and 12 hours indicated that high intensity UV-B lights or high temperature alone can cause sunburn respectively. The UV-B and temperature combination treatment enhanced the sunburn processes. The apples with sunburn caused under natural conditions or under UV-B and temperature controlled conditions were scanned by using reflectance spectroscopy of FOSS NIR system at different stage of the sunburn. The results indicted that Fuji apple sunburn can be efficiently detected at the early stage of sunburn in both natural and controlled conditions.