CELL-WALL MODIFICATION DURING RIPENING OF KEITT AND TOMMY ATKINS MANGO FRUIT

'Keitt' and 'Tommy Atkins' mango (Mangifera indica L.) fruit were evaluated for selected ripening criteria at six ripening stages, from mature green to overripe. 'Tommy Atkins' mangos developed more red and yellow pigmentation (CIE a* and b*) in peel and mesocarp tissues than 'Keitt'. The outer mesocarp of 'Keitt' remained firm longer than 'Tommy Atkins', and the inner mesocarp was softer than the outer at each stage in both cultivars. Cell wall neutral sugars, particularly arabinosyl, rhamnosyl, and galactosyl residues, decreased with ripening in both cultivars. 'Keitt' had more loosely associated, chelator-soluble pectin, accumulated more soluble polyuronides, and retained more total pectin at the ripe stage than 'Tommy Atkins'. Both cultivars had similar polygalacturonase (EC 3.2.1.15) activity which increased with ripening. The amount and molecular weight of cell wall hemicellulose decreased with ripening in both cultivars. These data indicate that enzymatic and/or nonenzymatic processes, in addition to polygalacturonase activity, are involved in the extensive softening of mango fruit.