Potential factors that contribute to resin canal discoloration in mango fruit

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

In-transit ripening of mango fruit: concepts and considerations

Refrigerated containers are used to transport mangoes over long distances. In Australia, mangoes grown in northern tropical production areas for the domestic market are transported by road and/or rail for up to 4000 km to southern ripening centres. There is no other viable option for growers to ripen their fruit. A current project is investigating sustained ethylene release systems for ripening mango fruit in road transport containers over an in-transit period of up to 4 days. This approach could potentially provide an alternative cost-effective ripening strategy for the mango industry. Studies have been and will be performed using shipments of 'B74' and 'Honey Gold' mango fruit, respectively, in refrigerated road containers. In-container environment monitoring, fruit shelf life and quality evaluation at outturn are carried out. Corresponding laboratory experiments that simulate transit are also to be conducted with a view to modelling mango fruit responses to in-transit conditions

Sources of vase life variation in cut roses: A review

In determining vase life (VL), it is often not considered that the measured VL in a particular experiment may greatly depend on both the preharvest and evaluation environmental conditions. This makes the comparison between studies difficult and may lead to erroneous interpretation of results. In this review, we critically discuss the effect of the growth environment on the VL of cut roses. This effect is mainly related to changes in stomatal responsiveness, regulating water loss, whereas cut flower carbohydrate status appears less critical. When comparing cultivars, postharvest water loss and VL often show no correlation, indicating that components such as variation in the tissue resistance to cavitate and/or collapse at low water potential play an important role in the incidence of water stress symptoms. The effect of the growth environment on these components remains unknown. Botrytis cinerea sporulation and infection, as well as cut rose susceptibility to the pathogen are also affected by the growth environment, with the latter being largely unexplored. A huge variability in the choices made with respect to the experimental setup (harvest/conditioning methods, test room conditions and VL terminating symptoms) is reported. We highlight that these decisions, though frequently overlooked, influence the outcome of the study. Specifications for each of these factors are proposed as necessary to achieve a common VL protocol. Documentation of both preharvest conditions and a number of postharvest factors, including the test room conditions, is recommended not only for assisting comparisons between studies, but also to identify factors with major effects on VL

Anatomy of skin disorders afflicting Australian mangoes

Lenticel discoloration (LD), under-skin browning (USB) and resin canal disorder (RCD) are three important fruit skin disorders of concern to the Australian mango industry. They result in downgrading of fruit quality and loss of market confidence. LD is confined to the discoloration of lenticels on the fruit skin. USB is a sub-surface spreading grey-brown lesion that may only become evident in the marketplace. RCD is a dark brown discoloration of the finely branched pattern of ramifying sub-surface resin canals. These three browning disorders were compared and contrasted at the cellular level by light microscopy after free-hand sectioning. Discoloured lenticels on the surface of 'Honey Gold' mango fruit typically appeared as small round spots comprised of a dark brown centre surrounded by a white corona. Non-coloured lenticels were visible as small round spots surrounded by a white corona. In cross-section, there was browning of cells surrounding the cavity of discoloured lenticels. Nonetheless, there was no such browning in non-coloured lenticels. USB symptoms in 'Honey Gold' fruit were evident as dark-brown cells in the tissue surrounding the resin ducts. In contrast, RCD, which was evident in 'Kensington Pride' mango fruit, was characterised by browning of the lumen of resin ducts. Accordingly, LD, USB and RCD involve different browning biology processes at the cell and tissue levels. A greater understanding of symptom development and expression could aid in informed management of these physiological disorders

Validation of the effects of a single one second hypochlorite floral dip on Botrytis cinerea incidence following long-term shipment of cut roses

The effect of a pre-shipment hypochlorite treatment on botrytis incidence was evaluated in a large number of rose cultivars and under different long-term storage conditions. Application parameters, stability and sources of hypochlorite were investigated. Irrespective of the type of packaging and shipment conditions, roses that received a pre-shipment treatment with 100 to 150 mg/L hypochlorite showed a significantly decreased botrytis incidence compared to non-hypochlorite treated roses. The hypochlorite treatment generally was more effective than a comparable treatment with commercial fungicides. Dipping the flower heads for approximately one second in a hypochlorite solution was more effective than spraying the heads. In few cases minor hypochlorite-induced damage on the petal tips was observed at higher concentrations (>200 mg/L). Apart from the effect on botrytis incidence, the treatment resulted in reduced water loss that may have an additional beneficial effect on the eventual flower quality. It is concluded that, apart from other obvious measures to reduce botrytis incidence (prevention of high humidity at the flower heads) a pre-shipment floral dip in 100 to 150 mg/L hypochlorite from commercial household bleach is an easy and cost effective way to reduce botrytis incidence following long term storage/transportation of roses. © 2015, International Society for Horticultural Science. All rights reserved