Maintaining mango (Mangifera indica L.) fruit quality during the export chain
Mangoes are tropical/sub tropical fruit with a highly significant economic importance. Preferable quality attributes include freedom from external damages such as bruises, latex or sap injury and decay, uniform weight, colour, aroma, firmness (with little give away, not soft), shape and size. The fruit is rich in antioxidants and recommended to be included in the daily diet due to its health benefits such as reduced risk of cardiac disease, anti cancer, and anti viral activities. Maintenance of mango fruit quality during the supply chain depends on many aspects including adequate orchard management practices, harvesting practices, packing operation, postharvest treatments, temperature management, transportation and storage conditions, and ripening at destination. Postharvest losses are high during the supply chain due to harvesting fruit at improper maturity, mechanical damage during the whole chain, sap burn, spongy tissue, lenticels discolouration, fruit softening, decay, chilling injury, and disease and pest damage. The aim of postharvest treatments and management practices in the supply chain is to create suitable conditions or environments to extend the storage life and retain the quality attributes, nutritional and functional compositions. This review summarises the available research findings to retain the overall mango fruit quality and to reduce postharvest losses during supply chain by adopting suitable postharvest novel technologies.
Mango Ripening & Quality Assessment
This program provides retailers with a marketing advantage to sell mangos by offering the U.S. consumer a quality fruit that is ripe and ready to eat. Extensive consumer research demonstrates that ripe fruit has a higher acceptance with consumers, leading to higher mango sales.
The program has enlisted a ripening expert to design, implement and evaluate a ripening program for mangos. The ripening expert travels to select importers, retailers, wholesalers, and fresh-cut processors to determine their ripening capabilities and assess all the technical factors that can affect the success of the program. The ripening expert also audits mango in-store displays and storage rooms to provide helpful insights and suggestions to improve ripening. Audits includes: display temperatures, mango quality (internal and external), size of the displays, items stored with mangos, hazards that could affect mango quality, backroom temperatures, rotation system, staff knowledge, and more.
Following these audits, the ripening expert works closely with Quality Control (QC) personnel to test mangos and create a pre-conditioning and ripening practical protocol that will deliver a ripe mango to consumers. The expert also assesses the impact of the program on mango sales and volume at the retail and importer level.
HOW TO USE THE MANGO MATURITY AND RIPENESS GUIDE
Evaluating mango quality at receiving is an issue for most receivers. The confusion over maturity, ripeness and quality continues to create challenges for the entire mango supply chain. The NMB is attempting to clear the confusion and provide understandable advice for quality assessment procedures.
MANGOS — THE SUPERFRUIT YOU LOVE
The charts are intended for use at the retail receiving point in the United States.
You should expect at least 90% of the mangos tested to fall in stage 2 or higher.
Experience and good judgment are still your best tools. Actual results may vary from these findings.
These charts are meant to be educational and to provide a guideline for understanding mango maturity and ripeness. They do not represent U.S. Federal Grade Standards and should not serve as the basis for a contract or for an control.
MANGO EXPECTATIONS AT RECEIVING
Mangos are harvested when mature, but not ripe.
A mature mango will ripen normally with increasing soluble solids content (degrees Brix) and decreasing firmness (lbs. force) to become ready to eat.
At receiving you can expect the mangos to be mature, but not necessarily ripe.
Maturity can be judged by a combination of factors, including internal color, firmness, degrees Brix and fruit shape.
Red skin is not an indicator of maturity, quality or ripeness and should not be used to evaluate mangos at receiving.
It is very typical to find mangos of differing maturity and ripeness in the same load and in the same box.
MEASURING MANGO MATURITY AND RIPENESS
Internal flesh color, which develops near the seed and will progress outward as shown in these photos, is generally the best indicator of maturity and ripeness. Firmness and degrees Brix ranges are provided as an additional reference.
To measure firmness with a fruit penetrometer, use a 5/16” (8 mm) tip and test the mango flesh with the skin removed
To measure degrees Brix with a refractometer, collect the flesh from an entire mango cheek or a plug taken down to the seed and juice the entire flesh sample
Full shoulders at the stem end may be an indicator that the mango was harvested mature and will ripen normally
An overview of preharvest factors influencing mango fruit growth, quality and postharvest behaviour
Mango, a tropical fruit of great economic importance, is generally harvested green and then commercialised after a period of storage. Unfortunately, the final quality of mango batches is highly heterogeneous, in fruit size as well as in gustatory quality and postharvest behaviour. A large amount of knowledge has been gathered on the effects of the maturity stage at harvest and postharvest conditions on the final quality of mango. Considerably less attention has been paid to the influence of environmental factors on mango growth, quality traits, and postharvest behaviour. In this paper, we provide a review of studies on mango showing how environmental factors influence the accumulation of water, structural and non-structural dry matter in the fruit during its development. These changes are discussed with respect to the evolution of quality attributes on the tree and after harvest. The preharvest factors presented here are light, temperature, carbon and water availabilities, which can be controlled by various cultural practices such as tree pruning, fruit thinning and irrigation management. We also discuss recent advances in modelling mango function on the tree according to environmental conditions that, combined with experimental studies, can improve our understanding of how these preharvest conditions affect mango growth and quality.
Mango is a climacteric fruit generally harvested green, which ripens during the marketing process (transport, storage etc.) with an irregular storage period between harvest and consumption. In addition to these market constraints, we must also take the high variability of preharvest and postharvest factors into account, as well as the difficulty to harvest fruit at an optimal maturity stage. All of these factors are involved in providing strong heterogeneous batches of mangoes in the supply chain in terms of fruit size, gustatory quality and postharvest behaviour.
Studies on mango dealing with the factors that determine the final quality of fruit at the consumer level have generally focused on maturity at harvest (Jacobi et al., 1995; Lalel et al., 2003a) and on postharvest management (Hoa et al., 2002; Nunes et al., 2007). However, as is the case with other stone fruits, pre-harvest cultural practices, which affect the environmental conditions of fruit development, profoundly influence postharvest performance and final quality (Crisosto et al., 1995; Hewett, 2006). Few studies related to the effects of environmental factors on mango quality before harvest have been carried out, and even less have focused on the interaction between preharvest and postharvest factors, whereas it is necessary to take these factors into account in order to propose technical solutions to improve final mango quality.
Fruit quality consists of many attributes, both intrinsic, including texture, sweetness, acidity, aroma, shelf life and nutritional value, and extrinsic, such as colour or size.
Mango is a fleshy fruit containing more than 80% water (Lakshimnarayana et al., 1970). Its size depends on the accumulation of water and dry matter in the various compartments during fruit growth. The skin, the flesh and the stone have specific compositions that appear to accumulate water and dry matter at different rates, depending on environmental conditions (Léchaudel et al., 2002). Fruit growth after cell division consists in the enlargement of fruit cells characterised by a large accumulation of water that results from the balance between incoming fluxes such as phloem and xylem, and outgoing fluxes such as transpiration (Ho et al., 1987). Changing the balance between these various fluxes, which have elastic and plastic components, leads to large variations in fruit volume. Mango dry matter mainly consists of carbohydrates, 60% of which are sugars and acids (Ueda et al., 2000), the main compounds contributing to fruit sweetness and acidity (Malundo et al., 2001). The amount of carbohydrates supplied to tree fruits depends on the amount produced by leaf photosynthesis, on sink demand and on the availability of the reserve pool. Also, from the point of view of fruit quality, it is essential to understand how preharvest factors influence source-sink relationships involved in fruit growth.
Fruit flesh taste is highly dependent on the balance between organic acids and soluble sugars, which are predominantly represented in mango by citric and malic acids, and sucrose, fructose and glucose, respectively (Medlicott and Thompson, 1985). The patterns of these compounds during mango development and maturation are well described, even if many studies deal with the evolution of fruit flesh composition during ripening according to harvest date. To our knowledge, only a few results of preharvest factor effects on mango taste have been reported.
Another quality trait for mango is its shelf life, which can vary with postharvest conditions, the best known of which is temperature. However, this attribute can be influenced by conditions during fruit growth that affect the supply of minerals to the fruit. In fact, relationships between minerals [the main one in mango is potassium, followed by magnesium and calcium; Simmons et al. (1998a)] and shelf life are often studied. In particular it appears that variations in calcium content or the ratio between calcium and the other two minerals delay ripening and senescence (Ferguson, 1984) or reduce storage disorders (Bangerth, 1979). Calcium is supplied by the xylem (Jones et al., 1983), and potassium and magnesium are phloem-mobile nutrients (Nooden, 1988). Special attention must also be paid to the influence of environmental factors on ingoing fruit fluxes as well as on the balance between mineral ions in mango, as has been done for other fruits (Ferguson et al., 1999). Moreover, shelf life can be discussed in terms of dry matter content, which is directly affected by carbohydrate and water fluxes at the fruit level during its growth.
Maturation of mango, a climacteric fruit, occurs in the final stages of fruit growth, resulting in a rise in respiration rate and ethylene production (Akamine and Goo, 1973). Since mango is generally harvested green, the onset of the climacteric phase is studied during fruit storage according to the maturity stage at harvest (Lalel et al., 2003a). However, these processes involved in mango maturation have been studied in some cases during fruit development (Reddy and Srivastava, 1999) and presented other components of ethylene biosynthesis, such as its immediate precursor, 1-aminocyclopropane-1-carboxylic acid (ACC) and a conjugated derivate, malonyl-ACC (Léchaudel and Joas, 2006). Moreover, changes in volatile aroma compounds, which are mainly produced during ripening, and in their precursors, such as fatty acids, have been reported to be related to ethylene production (Lalel et al., 2003b). Therefore, understanding the influence of preharvest conditions on mango maturation and the biosynthesis of secondary compounds (precursors or final products) is a necessary step to elucidate the determinism of nutritional and aromatic quality attributes.
The fruit is a complex system and it is difficult to take all of the environmental factors that affect its growth into account in the same experiment. A recent approach proposed by researchers was to build a model of mango fruit growth that integrated preharvest conditions. The first model functions at the branch level and takes the effects of changing source-sink relationships on fruit growth in dry mass into account by simulating the main processes involved, i.e. source activity, mobilisation of reserves, respiration and fruit demand (Léchaudel et al., 2005a). The second model is based on a biophysical representation of mango fruit growth in water mass and takes account of both reversible elastic and irreversible plastic components of growth (Léchaudel et al., 2007). This model predicts diurnal and seasonal variations of fresh mass and fruit water relationships after the period of cell division on the basis of climatic data and fruit dry mass. By combining the two models, a global model of mango functioning was proposed to simulate changes in fruit size and flesh composition at the branch level in terms of sugar, acid and mineral content, for example, according to climatic data, environmental factors, and 'initial' fruit size (Léchaudel et al., 2006).
The ‘Tommy Atkins’ mango genome reveals candidate genes for fruit quality
Mango, Mangifera indica L., an important tropical fruit crop, is grown for its sweet and aromatic fruits. Past improvement of this species has predominantly relied on chance seedlings derived from over 1000 cultivars in the Indian sub-continent with a large variation for fruit size, yield, biotic and abiotic stress resistance, and fruit quality among other traits. Historically, mango has been an orphan crop with very limited molecular information. Only recently have molecular and genomics-based analyses enabled the creation of linkage maps, transcriptomes, and diversity analysis of large collections. Additionally, the combined analysis of genomic and phenotypic information is poised to improve mango breeding efficiency.
Results
This study sequenced, de novo assembled, analyzed, and annotated the genome of the monoembryonic mango cultivar ‘Tommy Atkins’. The draft genome sequence was generated using NRGene de-novo Magic on high molecular weight DNA of ‘Tommy Atkins’, supplemented by 10X Genomics long read sequencing to improve the initial assembly. A hybrid population between ‘Tommy Atkins’ x ‘Kensington Pride’ was used to generate phased haplotype chromosomes and a highly resolved phased SNP map. The final ‘Tommy Atkins’ genome assembly was a consensus sequence that included 20 pseudomolecules representing the 20 chromosomes of mango and included ~ 86% of the ~ 439 Mb haploid mango genome. Skim sequencing identified ~ 3.3 M SNPs using the ‘Tommy Atkins’ x ‘Kensington Pride’ mapping population. Repeat masking identified 26,616 genes with a median length of 3348 bp. A whole genome duplication analysis revealed an ancestral 65 MYA polyploidization event shared with Anacardium occidentale. Two regions, one on LG4 and one on LG7 containing 28 candidate genes, were associated with the commercially important fruit size characteristic in the mapping population.
Conclusions
The availability of the complete ‘Tommy Atkins’ mango genome will aid global initiatives to study mango genetics.
Background
Mangoes are an important fruit crop grown in over 103 countries across the tropical and subtropical zones. The common mango is typically a large, tropical, and evergreen tree with an upright to spreading dense canopy that can reach up to 30 m in some climates if not pruned. Mango production is estimated to be over 50 million metric tons (Mt) per annum from an area of over 56.8 million hectares [1, 2]. India is by far the largest mango producer with 41.6% of world production (18 Mt) followed by China with 10% (4.5 Mt). The bulk of production is grown and consumed locally with only approximately 9.5 Mt exported due to the high local consumption in the countries of origin and the highly perishable nature of the fruit [1, 3].
Mango (Mangifera indica L.) belongs to the family Anacardiaceae. Based on morphological characters there are thought to be from 45 [4] to 69 [5] species within the Mangifera genus originating mainly in tropical Asia, with the area of highest diversity found in western Malesia [6]. The common mango, M. indica, was domesticated at least 4000 years ago, and further developed from an origin in the Assam Valley close to the western border of the Myanmar-Indochinese area in the Quaternary period and spread throughout the Indian subcontinent [6,7,8]. A further 26 species also have edible fruit, including M. altissima, M. caesia, M. foetida, M. kemang, M. laurina, M. odorata, M. pajang and M. pentandra being traditionally consumed in various Southeast Asian communities [9,10,11].
Although domestication and selection of mango varieties have occurred for thousands of years, the systematic breeding of mangoes is relatively recent, compared with many temperate tree fruit crops. Systematic mango breeding is a long term endeavor (up to 25 years) due to long juvenility, polyembryony, and very low fruit retention that reduce breeding efficiency and add time to the breeding generation cycle [12]. As a result, the general understanding of mango genetics and trait heritability has been limited. In more recent times, systematic breeding programs have aimed to develop varieties with production, consumer, and transportability traits more suited for national and international markets. Breeding mangoes with improved traits like reduced tree vigor, regular high yields, disease tolerance, long shelf life, optimal fruit size, shape, color, and high eating qualities are of primary interest to improve production efficiency and consumer demand [12, 13].
‘Tommy Atkins’ comes from a relatively recently developed group of cultivars that originated in Florida, USA, as chance seedlings in the early part of the twentieth century [14,15,16]. Their success is partly attributed to their relatively higher yields, large fruit size, strong blush color, lower vigor canopies, and adaptability across tropical and subtropical regions. This group originated from the high yielding monoembryonic cultivar ‘Mulgoba’ imported from India to the USA in 1910. An early seedling selection from ‘Mulgoba’ was named “Haden” which itself gave rise to the monoembryonic cultivars ‘Keitt’, ‘Kent’, and ‘Tommy Atkins’ that dominate international trade. Another cultivar, ‘Kensington Pride’, has dominated Australian production for the past century and is only now slowly being replaced by newer cultivars that generally have ‘Kensington Pride’ in their pedigree. The pre-Australian origin of ‘Kensington Pride’, prior to its introduction at Port Denison (now Bowen) between 1885 and 1889, is unknown. ‘Kensington Pride’ has a distinctive flavor and aroma not common in other Indian or Floridian cultivars. Its shape and red blush color suggest it has an Indian sub-continent origin, while its polyembryonic nature suggests a Southeast Asian origin. It has been suggested that ‘Kensington Pride’ is possibly a hybrid with Indian and Southeast Asian parentage [17].