Loss of watercore from `Fuji' apple observed by magnetic resonance imaging

Abstract Watercore is a physiological disorder affecting apples in which intercellular spaces are filled with liquid. Proton magnetic resonance imaging ( 1 H-MRI) was used to investigate its postharvest amelioration in `Fuji' apple ( Malus domestica Borkh.)—a cultivar where spatial distribution of affected tissue is manifest in two distinct forms (block and radial watercore), and curing leads to fruit of normal appearance and taste. Badly-affected fruit were identified by imaging after harvest in each of two seasons, and in one season, the two forms were compared. A semi-quantitative analysis of the curing dynamics, and a description of the spatial clearing in parenchyma tissue was obtained based upon serial analysis of 2-dimensional multi-slice images (echo time ( T E )=40 ms; repetition time ( T R )=1000 ms) and volume rendering of 3-dimensional (3D) data arrays acquired from individual fruit during storage (20 weeks, 0°C). Results indicated that the proportion of watercore-affected tissue decreased linearly with time, irrespective of disorder pattern. However, the length of time taken for symptoms to disappear depended on the severity of the disorder at harvest. Percent water-soaked tissue was greatest in central image slices and least in slices nearest the surface in both transverse and longitudinal sections. The distribution of affected tissue between basal and distal hemispheres of the fruit was season-dependent. A basic spin-echo pulse sequence was sufficient to exploit relaxation differences between tissues in 3D data arrays. Differentiating between saturated tissue as opposed to unaffected tissue ( T E =20 ms; T R =200 ms), or saturated vs. vascular tissue ( T E =5 ms; T R =150 ms) was achieved by altering T E and T R . By reconstructing images with equivalent fields-of-view from within these arrays it was possible to explore relationships between vascular tissue and watercore-affected areas in 3D space.