Potential factors that contribute to resin canal discoloration in mango fruit

Abstract

Resin canal discoloration (RCD) is a quality defect that reduces the visual appeal and marketability of mango fruit. Market reports of RCD have increased recently, particularly for 'Kensington Pride' fruit produced in the Northern Territory, Australia. Anecdotal observations by mango growers suggest that early fruit harvest maturity, rain before harvest and handling conditions may be associated with RCD. In the current study, we completed a series of preliminary experiments with 'Kensington Pride' fruit to characterise RCD symptom development and to identify potential contributing factors. RCD was seldom present in hard green-mature fruit at harvest. The defect was first visualised as lightly discoloured resin canals in partially ripe fruit. The severity of RCD symptoms steadily increased as fruit developed from firm-ripe to eating-ripe. The incidence of RCD was 42-52% higher for fruit picked early in the season at KLEINERDAN13% dry matter content (DMC) than for those harvested 2-4 weeks later at 15-17% DMC. Harvesting fruit within 12 h of a 14-mm rainfall event resulted in 45% higher RCD incidence than in fruit picked after 60 h of sustained dry weather. The incidence of RCD varied from 0 to 45% for fruit from nine orchards in the Northern Territory when harvested and ripened directly off the tree. RCD incidence was threefold higher in the same fruit that were exposed to commercial handling and interstate transport. Overall, these observations suggest that RCD is a complex disorder that occurs when field conditions result in sensitised fruit that may express the defect when exposed to postharvest handling practices.