TY - JOUR

T1 - Structural and physiological changes associated with the skin spot disorder in apple

AU - Grimm, Eckhard

AU - Khanal, Bishnu P.

AU - Winkler, Andreas

AU - Knoche, Moritz

AU - Köpcke, Dirk

N1 - Funding Information: This work was funded in part by grants from the Niedersächsisches Ministerium für Wissenschaft und Kultur (grant no. 76251-17-4/09/ZN2543 ) and AgroFresh Inc . We thank Peter Grimm-Wetzel, Jörg Hilbers and Rolf Kirchhof for excellent technical support, the fruit growers of the Altes Land for providing fruit samples, Hans de Wild (AgroFresh Inc.) for useful discussion and Sandy Lang for critical comments on an earlier version of this manuscript.

PY - 2012/2

Y1 - 2012/2

N2 - Skin spot is an important physiological disorder of 'Elstar' apples (Malus×domestica Borkh.) that occurs after fruit have been removed from controlled atmosphere storage. Skin spots are irregular patches of small, round, brown blemishes. Cross-sections reveal a browning of protoplasts (coagulated) and of cell walls that extends into the hypodermis. Skin spots are always associated with linear, gaping and non-gaping microcracks in the cuticle. Staining of apple skin with calcofluor white usually results in white fluorescence of cell walls but, within a skin spot, the white fluorescence is weak or absent. Cell walls within, and in the immediate vicinity of skin spots stain with phloroglucin/HCl indicating the presence of lignin. The area of skin affected by skin spots was positively and linearly correlated with the area of the non-blush fruit surface infiltrated by acridine orange. In general, skin spots were limited to the non-blush fruit surface and occurred more frequently near the stem-end than the calyx region of the fruit. Skin spot areas were correlated with a 2.5-fold increase in water vapour permeability compared with unaffected areas (23.8±4.0ms-1 with skin spots, 9.6±2.1×10-5ms-1 without skin spots). Strips of the fruit skin from regions with skin spots had an increased maximum force and modulus of elasticity. Dipping fruit in ascorbic acid (0.1 or 0.3mM for 10min) before storage decreased the area affected by skin spots. There was no effect of dipping in ethanol/water (70%, v/v, 15min) or in solutions of captan (1.5gL-1, 10min) or trifloxystrobin (0.1gL-1, 10min). In contrast, prestorage treatment with 1-methylcyclopropene (630nLL-1 for 24h) or poststorage incubation in H2O2 (10% for 2, 6, 10 and 16h) increased skin spots. Our data are consistent with a typical cell response to an oxidative burst that seems to be focussed on particular regions of the 'Elstar' fruit surface by concentrations of cuticular microcracks, and that is possibly caused by reoxygenation injury upon removal from CA storage.

AB - Skin spot is an important physiological disorder of 'Elstar' apples (Malus×domestica Borkh.) that occurs after fruit have been removed from controlled atmosphere storage. Skin spots are irregular patches of small, round, brown blemishes. Cross-sections reveal a browning of protoplasts (coagulated) and of cell walls that extends into the hypodermis. Skin spots are always associated with linear, gaping and non-gaping microcracks in the cuticle. Staining of apple skin with calcofluor white usually results in white fluorescence of cell walls but, within a skin spot, the white fluorescence is weak or absent. Cell walls within, and in the immediate vicinity of skin spots stain with phloroglucin/HCl indicating the presence of lignin. The area of skin affected by skin spots was positively and linearly correlated with the area of the non-blush fruit surface infiltrated by acridine orange. In general, skin spots were limited to the non-blush fruit surface and occurred more frequently near the stem-end than the calyx region of the fruit. Skin spot areas were correlated with a 2.5-fold increase in water vapour permeability compared with unaffected areas (23.8±4.0ms-1 with skin spots, 9.6±2.1×10-5ms-1 without skin spots). Strips of the fruit skin from regions with skin spots had an increased maximum force and modulus of elasticity. Dipping fruit in ascorbic acid (0.1 or 0.3mM for 10min) before storage decreased the area affected by skin spots. There was no effect of dipping in ethanol/water (70%, v/v, 15min) or in solutions of captan (1.5gL-1, 10min) or trifloxystrobin (0.1gL-1, 10min). In contrast, prestorage treatment with 1-methylcyclopropene (630nLL-1 for 24h) or poststorage incubation in H2O2 (10% for 2, 6, 10 and 16h) increased skin spots. Our data are consistent with a typical cell response to an oxidative burst that seems to be focussed on particular regions of the 'Elstar' fruit surface by concentrations of cuticular microcracks, and that is possibly caused by reoxygenation injury upon removal from CA storage.

KW - Antioxidants

KW - Controlled atmosphere

KW - Cuticle

KW - Malus×domestica

KW - Microcrack

KW - Skin disorder

UR - http://www.scopus.com/inward/record.url?scp=80755184732&partnerID=8YFLogxK

U2 - 10.1016/j.postharvbio.2011.10.004

DO - 10.1016/j.postharvbio.2011.10.004

M3 - Article

AN - SCOPUS:80755184732

VL - 64

SP - 111

EP - 118

JO - Postharvest biology and technology

JF - Postharvest biology and technology

SN - 0925-5214

IS - 1

ER -