RESUMEN
Changes in quality, phytochemical content and cell wall metabolism of two loquat cultivars (Eriobotrya japonica cvs. 'Morphitiki', 'Karantoki') under different storage regimes were studied. The fruit were harvested at commercial maturity stage and analyzed after 1, 3, 5, 7, and 11 days maintenance at room temperature (RT, â¼ 20°C) or after cold storage (14 days at 4°C) and additional ripening at RT for 1, 3 and 5 days, respectively. Compositional analysis revealed substantial cultivar differences; the 'Morphitiki' fruit was more acidic and showed higher contents of total phenolics, flavonoids and hydroxycinnamic acid-derivatives as well as greater antioxidant potency. Although firmness did not change markedly during storage, the cell wall exhibited extensive remodeling. Greater changes were observed in the pectin backbones than in polyuronide side chains and cross-linking glycans. Polygalacturonase (PG) showed better association with cell wall solubilization at RT than the enzymes involved in arabinan or galactan disassembly. During postharvest ripening after harvest, 'Karantoki' showed more extensive pectin solubilization than 'Morphitiki'. Interestingly, cold storage inhibited the cell wall disassembly in 'Karantoki' but not in 'Morphitiki', suggesting that the cultivars may differ in their susceptibility to chilling-related wall disorders. Low temperature-induced alterations in wall disassembly may impact juice and phytochemical release upon consumption.
Asunto(s)
Antioxidantes/química , Pared Celular/metabolismo , Eriobotrya/química , Almacenamiento de Alimentos/métodos , Extractos Vegetales/química , Antioxidantes/metabolismo , Pared Celular/química , Eriobotrya/clasificación , Eriobotrya/citología , Eriobotrya/metabolismo , Frutas/química , Frutas/metabolismo , Pectinas/química , Pectinas/metabolismo , Extractos Vegetales/metabolismo , Polisacáridos/química , Polisacáridos/metabolismoRESUMEN
Fruit ripening is characterized by processes that modify texture and flavor but also by a dramatic increase in susceptibility to necrotrophic pathogens, such as Botrytis cinerea. Disassembly of the major structural polysaccharides of the cell wall (CW) is a significant process associated with ripening and contributes to fruit softening. In tomato, polygalacturonase (PG) and expansin (Exp) are among the CW proteins that cooperatively participate in ripening-associated CW disassembly. To determine whether endogenous CW disassembly influences the ripening-regulated increase in necrotropic pathogen susceptibility, B. cinerea susceptibility was assessed in transgenic fruit with suppressed polygalacturonase (LePG) and expansin (LeExp1) expression. Suppression of either LePG or LeExp1 alone did not reduce susceptibility but simultaneous suppression of both dramatically reduced the susceptibility of ripening fruit to B. cinerea, as measured by fungal biomass accumulation and by macerating lesion development. These results demonstrate that altering endogenous plant CW disassembly during ripening influences the course of infection by B. cinerea, perhaps by changing the structure or the accessibility of CW substrates to pathogen CW-degrading enzymes. Recognition of the role of ripening-associated CW metabolism in postharvest pathogen susceptibility may be useful in the design and development of strategies to limit pathogen losses during fruit storage, handling, and distribution.