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The mango cultivar ‘Apple’ is an important fruitcrop in Kenya, but it is highly susceptible to russeting. The objective was to establish whether lenticels predispose cv. ‘Apple’ mango to russeting. Fruit mass and surface area increased in a sigmoidal pattern with time. The frequency of lenticels per unit surface area decreased during development. The number of lenticels per fruit was constant. Lenticels were most frequent in the apex region and least common in the cheek and nak (ventral) regions. The cheek region also had lenticels with the largest core areas, whereas the lenticel core areas in the apex region were significantly smaller. Microscopy revealed stomata became covered over with wax deposits at 33 days after full bloom (DAFB). By 78 DAFB, periderm had formed beneath the pore. At 110 and 161 DAFB, cracks had developed and the periderm had extended tangentially and radially. The presence of lenticels increased the strain released upon excision of an epidermal segment, further strain releases occurred subsequently upon isolation of the cuticle and on extraction of the cuticular waxes. The number of lenticels per unit surface area was negatively correlated with the fruit surface area (r2 = 0.62 **), but not affected by fruit size. Mango cv. ‘Apple’ had fewer, larger lenticels and more russet, compared with ‘Ngowe’, ‘Kitovu’ or ‘Tommy Atkins’ mango. In cv. ‘Apple’, the lowest lenticel frequency, the largest lenticels and the most russeting occurred at a growing site at the highest altitude, with the highest rainfall and the lowest temperature. Moisture exposure of the fruit surface resulted in enlarged lenticels and more microcracking of the cuticle. Our results establish that russeting in ‘Apple’ mango is initiated at lenticels and is exacerbated if lenticels are exposed to moisture.

PR, IFPRI4; 1 Fostering Climate-Resilient and Sustainable Food Supply, Development Strategies and Governance (DSG); Transformation Strategies, Management of postharvest food loss and waste (FLW) is an important strategy in efforts to sustainably meet the food and nutrition needs of the world’s growing population. Sustainable food systems are critical to achieving food security and nutrition for all, now and in the future. Food systems cannot be sustainable when a large proportion of the food produced using limited resources is lost or wasted in the supply chain. At the global level, it is estimated that poor postharvest management means this is the case for 30 percent of the food produced for human consumption (FAO 2011, 2019). The figure for Kenya is similar (Ministry of Agriculture, Livestock, Fisheries and Cooperatives 2018). The 2021 Food Waste Index Report (UNEP 2021) indicates that every Kenyan wastes about 100 kg of food every year, which adds up to 5.2 million metric tons1 per year, excluding food loss that happens upstream, from production to retail. In monetary terms, wasteful consumption accounts for slightly over US$500 million annually (Mbatia 2021). FLW exac erbates food insecurity and has negative impacts on the environment through waste of precious land, water, farm inputs, and energy used in producing food that is not consumed. In addition, postharvest losses, caused by poor storage conditions, reduce income to farmers and contribute to higher food prices.

Exposure to surface moisture triggers cuticular microcracking of the fruit skin. In mango fruit cv. apple, microcracking compromises postharvest performance by increasing moisture loss and infections with pathogens. This study reports the effects of exposing the fruit’s skin to surface moisture on the incidence of microcracking and on water vapor permeance. Microcracking was quantified microscopically following infiltration with a fluorescent tracer. Water mass loss was determined gravimetrically. Moisture exposure increased cuticular microcracking and permeance. During moisture exposure, permeance increased over the first 4 d, remained constant up to approximately 8 d, then decreased for longer exposure times. Fruit development followed a sigmoid growth pattern. The growth rate peaked approximately 103 days after full bloom. This coincided with the peak in moisture-induced microcracking. There were no increases in water vapor permeance or in microcracking in control fruit that remained dry. When experimental moisture exposure was terminated, microcracking and water vapor permeance decreased. This suggests a repair process restoring the barrier properties of the fruit skin. Histological analyses reveal a periderm forms in the hypodermis beneath a microcrack. Our study demonstrates that surface moisture induces microcracking in mango cv. apple that increases the skin’s water vapor permeance and induces russeting.

During ripening, European pear (Pyrus communis L. cv. ‘La France’) fruit undergo dramatic softening in response to increased ethylene production, whereas Chinese pear (Pyrus bretschneideri Rehd. cv. ‘Yali’) fruit remain firm, despite producing large amounts of ethylene. The molecular basis of this differential softening behavior is not well understood. In this study, we combined a yeast-based signal sequence trap (YSST) and macroarray gene expression analysis to identify putative genes encoding secreted proteins that control pear fruit softening. We identified 22 cDNAs annotated as encoding proteins with diverse cell wall-associated functions that were up- or down-regulated during fruit ripening in ‘La France’. Gene expression analysis in fruit that were treated with the ethylene perception inhibitor 1-methylcyclopropene (1-MCP) at 4 d after the onset of ripening revealed that 16 of the targeted genes are ethylene-regulated, while the others appear to be ethylene independent. Comparative gene expression analyses of ‘La France’ and ‘Yali’ fruit during ripening suggested that four ethylene-regulated cDNAs encoding cell wall modifying proteins, contig 2 (polygalacturonase 3), contig 15 (expansin), contig 19 (expansin) and contig 55 (pectate lyase) contribute to the different softening behaviors of ‘La France’ and ‘Yali’ fruit. Additionally, one ethylene-independent cell wall related gene, contig 36 (expansin), and three genes encoding proteins of unknown function, contigs 1, 13 and contig 75 showed differential expression between ‘La France’ and ‘Yali’ fruit during ripening. The results presented herein represent promising candidates for future functional analysis and elucidation of softening mechanisms.