Learn More About Mangosteen

The botany of the mangosteen is as follows: the Latin name of the mangosteen is Garcinia mangostana L. The genus Garcinia is named in honor of Laurent Garcin, a French 18th-century explorer and plant collector. Linnaeus, the “L” after the species name mangostana, honored his work by naming the genus Garcinia after him. 
 
Besides the mangosteen, there are numerous other species within the genus, many of which produce edible fruit, but none as exquisite as the mangosteen. Some produce valuable gums, waxes, and dyes. I will say that although the word “mango” is contained in the word “mangosteen,” there is no relationship botanically. Mangoes and mangosteens are not at all related at the genus or family levels, but only share several of the same letters. 
 
Going up the scale or hierarchy, the genus Garcinia falls in the plant family Clusiaceae. This is the new name for the family and the replacement for the former family name, Guttiferae. This change was made several years ago by the International Botanical Nomenclature Organization. Further botanical descriptions are available online as well as in botany texts, and I will leave it to those who seek more of the technical description to go to those sources directly. 
 
An excellent text and source for vast amounts of technical information on numerous tropical fruits and nuts can be found in “Plant Resources of South-East Asia No. 2. Edible Fruit and Nuts.” (1992). This book, by E. W. M. Verheij and R. E. Coronel, is a wonderful resource that provides details for all levels of scholarship. 
 
Some traits of the mangosteen bear further discussion because they have played a major role in limiting the extent to which mangosteens have been planted around the globe. For example, the seeds of the mangosteen are considered “recalcitrant.” This means that they are very short-lived and must be kept moist, or they die almost as soon as they dry out. 

Mangosteen seeds can be kept alive in moist peat moss for weeks, and this is how they are usually shipped to distant locations. Holding the mangosteen seeds in a moist medium to keep them alive also causes them to immediately begin trying to sprout. 
 
Mangosteen trees are dioecious, meaning that there are male trees and female trees. The only problem with this is that, to date, no one has been able to find a male tree anywhere in the world, so if they exist, they are quite rare. Globally, it is possible that there have never been any male mangosteen trees. This places the entire burden on the female tree to perpetuate the species. No males mean no pollen, even though the female flower contains rudimentary sterile anthers where pollen would normally be found. 
 
Without pollen, there is no way to fertilize the female flower and create true seeds with variable genetic traits. Instead, the female mangosteen trees succeed in perpetuating the species by a process known as apomixis or agamospermy. The wall lining the ovary of the female flower, the nucellus, supplies the material that will then develop within the fruit segments and become what is effectively an asexually produced seed. As a result of this, it produces a clone of the mother tree. 
 
In a manner reminiscent of a potato tuber, the seed does not have the normal internal structure found in most plant species’ seeds, and it can be planted in any orientation, sprouting a new shoot from the highest point underground. There also appears to be no root hair development in mangosteen, which may negatively affect nutrient uptake. The involvement with mycorrhizal organisms plays a major role in the mangosteen’s ability to get what it needs from the soil. Further impeding the chances of survival, the seed size corresponds to seedling size and vigor, and small seeds are not worth planting as they retard the initial development. 

And then there is the last problem with growth in the early months. The tap root that forms appears to be adapted to little more than water uptake, and during the first six months or more, the seedling lives almost exclusively off the contents of the seed’s initial nutrient supply. It is only after overcoming all of these hurdles that the mangosteen plant can then continue its already challenged existence. And it proceeds in a similar vein over the next few years before reaching maturity and producing fruit. This is because the mangosteen seedling goes through what is known as a juvenile period with stringent requirements as to light levels and water supply. 
 
Many tropical trees have a juvenile period where they slowly grow upwards from the heavily shaded forest floor, gradually reaching for the brighter canopy above. This is often accompanied by a leaf structure that is quite different from that of the mature tree’s leaves and is more efficient for light absorption. In many cases, this is a survival strategy; it enables seedlings that happen to land and sprout in a low-light location to bide their time, hoping for a chance at better light levels later. 
 
In the case of the mangosteen, this period can go on for decades. In part, this has given the mangosteen the mistaken reputation of requiring 10 or more years to reach maturity and fruit production. Simply not true. Under ideal conditions (plant nursery), the first fruit can be as early as six years after the seed sprouts, but the initial low light period is still essential for about the first two years. 
 
Since there is no pollen source and therefore no sexual fertilization, there is no crossing and mixing of the genes that would provide a means for variety development and selection. It can take place, but will require lab techniques to manipulate the movement of genetic material within the nucleus and other structures of the cell. This feature in plants is not all that rare. Lawn grass seeds result from this kind of ‘seed’ production, and it is a benefit where uniformity is desired.

Because the seed does not arise from fertilization, genetic variation was thought to be almost nonexistent. Most written resources make mention of this lack of variation or attribute any distinct phenotypes (visually observable expression of the genes) to subtle differences in the environment in which the trees are planted. In other words, amongst one hundred trees in a field together, the small differences in soil structure, chemistry, or water retention from one spot to the next might account for any visual differences in the appearance of the trees or their fruit. In large part, it could, but it turns out there is much more going on at the genetic level. 
 
Since the seed arises from the cell wall of the female tree’s flower and is effectively a clone of the mother tree, the seedling has her genes intact and unchanged for generation after generation. This has led many to conclude that all of the mangosteen trees in the world are genetically identical, but this is most definitely not so (2, 3). Several experiments have been conducted taking advantage of the most current DNA and RNA analysis techniques, and it turns out that there is significant variation globally amongst the different populations of the mangosteen. There is a large proportion that has essentially the same genetic make-up (genotype), but there are significant numbers that do not. 

This brings me to a discussion of the chromosomes of the mangosteen. I will say that work is being done now to try to further our understanding of the genetics of the mangosteen because it has such great potential as a fruit tree crop. To date, no one has published a paper that can state the number of chromosomes in the mangosteen with any certainty, but this could change any day. Known as a karyotype, the chromosome count has been reported with such a wide variation in number as to be considered an unknown. The key question being looked at is, did the mangosteen arise as a result of a rare cross between two different Garcinia species (1)? And if it did, does this relatively rare event, the crossing of two species, explain in part the difficulty in producing progeny of both genders of trees, having viable pollen, or exhibiting a very slow initial growth rate? 
 
These questions, when answered, will go a long way in helping researchers to develop new cultivars (cultivated varieties) of this wonderful fruit. It is possible that the mangosteen is a result of a cross between two Garcinia species that had double their usual chromosome count (polyploidy), enabling them to interbreed and produce sterile offspring. During cell division, each double set of chromosomes (homologous pair) would be able to find the complementary other chromosome to pair up with and then enable cell division to proceed to completion. As unlikely as this series of events might seem, it has happened many times in the plant kingdom. It is possible that the mangosteen has happened more than once and at different locales. 
 
In addition to mutation and genetic drift, this could help to explain some of the variation found in genetic samples. This could also help researchers to create new mangosteen lines by determining which are the parent species. One could then manipulate their chromosome count, enabling the crossing of the two species to create new varieties. 

The mangosteen has historically been praised (see History and Folklore) for countless centuries by all who encountered it. The edible interior is renowned for its indescribable sweet-sour melting rush of flavors. But apart from the edible treasure inside the hull, the rind (technically a pericarp) has also been part of Ayurvedic medicine and has been valued throughout its native range for its medicinal qualities. The rind possesses a great diversity of complex organic chemicals (see Duke below), amongst which are tannic acid and xanthones. Xanthones comprise much of the promotional claims, but it may well be the tannic acid that explains why it has been used almost exclusively as an astringent and aid in controlling dysentery, diarrhea, and so on. 
 
For the last several centuries, the primary medicinal use of the rinds of the mangosteen has been for a disease, dysentery, that rarely ever appears anymore in present-day America or most of Europe. In fact, the rind contains so much tannic acid that it was suggested by someone in the 19th century (New York Times, October 27, 1881) that they be sent in bulk to the US to aid in the tanning of leather. According to this article, it made sense because the mangosteen rinds contained more tannin than was found in oak bark! 
 
This raises a question as to the palatability of a mangosteen product that claims to be a whole fruit formulation. It would be much too bitter to consume unless the extract was chemically modified or was so dilute it could be masked by sweeteners. Imagine the flavor if you placed an entire grapefruit in a blender, bitter rind and all. 
 
As to making a juice out of just the edible interior portion, you might lose out on most or all of the complex xanthones found in the rind. Thus, there is a need for the whole fruit. And since the USDA does not permit the import of fresh mangosteens from anywhere in Southeast Asia as of this writing, the fruit, if processed in the US, would have to be frozen before it could gain entry.