Superficial Scald and Bitter Pit Development in Cold-Stored Transgenic Apples Suppressed for Ethylene Biosynthesis

• Published in: Journal of agricultural and food chemistry 2009-04, Vol.57 (7), p.2786-2792
• Main Authors: Pesis, Edna, Ibáñez, Ana M, Phu, My Lin, Mitcham, Elizabeth J, Ebeler, Susan E, Dandekar, Abhaya M
• Format: Article
• Language: English
• Subjects: 1-aminocyclopropane-1-carboxylate synthase; alpha-farnesene; Amino Acid Oxidoreductases - genetics; Amino Acid Oxidoreductases - metabolism; aminocyclopropanecarboxylate oxidase; apples; Biological and medical sciences; bitter pit; carbon dioxide; cell respiration; Chemical Changes Induced by Processing/Storage; cold storage; Cold Temperature - adverse effects; ethylene production; Ethylenes - biosynthesis; farnesene; Food industries; Food Preservation - methods; food storage; Fruit - metabolism; Fruit and vegetable industries; Fundamental and applied biological sciences. Psychology; gene silencing; genetically modified foods; Lyases - genetics; Lyases - metabolism; Malus - genetics; Oxidation-Reduction; Plants, Genetically Modified - metabolism; postharvest diseases; postharvest physiology; Sesquiterpenes - metabolism; storage quality; superficial scald
• ISSN: 0021-8561; 1520-5118
• DOI: 10.1021/jf802564z

The plant hormone ethylene regulates climacteric fruit ripening and plays a major role in the development of superficial scald in apple fruits during cold storage. The effect of cold storage at 0 °C on development of superficial scald and bitter pit (BP) in transgenic Greensleeves (GS) apples suppressed for ethylene biosynthesis was investigated. Four apple lines were used: untransformed GS; line 68G, suppressed for 1-aminocyclopropane-1-carboxylic acid (ACC) oxidase (ACO); and lines 103Yand 130Y, suppressed for ACC synthase (ACS). Fruits from the transformed lines 68G, 103Y, and 130Y produced very little ethylene during 3 months of cold storage at 0 °C and after subsequent transfer to 20 °C, whereas untransformed fruits produced significant ethylene during cold storage, which increased dramatically at 20 °C. Respiration, expressed as CO2 production, was similar in all four apple lines. After 2 months at 0 °C, all apple lines showed some BP symptoms, but lines 68G and 103Y were more affected than untransformed GS or line 130Y. Both transformed and untransformed apples produced α-farnesene, but concentrations were lower in yellow fruit than in green fruit in all lines but 68G. Line 68G produced the most α-farnesene after 2 months at 0 °C, including both (E,E) α-farnesene and (Z,E) α-farnesene. Concentrations of (E,E) α-farnesene were 100 times greater than those of (Z,E) α-farnesene in all lines. After 4 months at 0 °C plus 1 week at 20 °C, untransformed GS apples exhibited the most superficial scald, whereas fruits from lines 68G and 103Y were less affected and line 130Y had no scald. Superficial scald severity was higher in green fruit than in yellow fruit in all affected lines. These lines also exhibited significant production of 6-methyl-5-hepten-2-one (MHO), a major oxidation product of (E,E) α-farnesene. Line 130Y neither exhibited superficial scald nor produced MHO. It is shown here that even transgenic apples suppressed for ethylene biosynthesis genes can produce α-farnesene, which in turn can oxidize to free radicals and MHO, leading to scald development.