Growing the ‘turtle liver’ is our greatest horticultural achievement!
Commencing in 2006, Dokmai Garden is continuously building up a collection of plants, thereby also attracting wild birds, butterflies and mushrooms. We surpassed 1000 plant species earlier this year and so many people ask questions like ‘how can you keep track of all plants’ and ‘which plant is your favourite’?
By mapping and recording all plants, and by blogging about them, the plants and other organisms are documented. That is a good help for your memory. As to which one is a favourite, it is a hard question to answer. The one I am looking at is usually my favourite, i.e. favourites change as I walk through the garden. All plants are darlings with their own special characteristics. Of course, all gardeners try the climatological limits, and an ‘impossible-to-grow-plant’ always challenges the gardener outside the plant’s natural range. A success brings pride. We manage to create an acceptable environment, and so we rejoice that we understand a piece of flora, although hardly anyone cares.
How about growing something nobody else in the world has grown?
Back in 2007 the Swedish ‘Karljohanstiftelsen’ awarded a Thai researcher, Saisamorn Lumyong at the Chiang Mai University, for her promising research on an edible mushroom, the mango bolete, Phlebopus (Phaeogyroporus) portentosus. This bolete has many names in Thai, including ‘hed ha’, ‘hed pung’ and ‘hed ta(p) tao’. The latter name translates to ‘turtle liver’, and indeed this dark mushroom which is currently for sale in the Chiang Mai markets may not look appetizing. It is! Saisamorn brought several kilogrammes of mango bolete to the banquet in Uppsala in Sweden and the guests agreed this mushroom is more delicious than the French cepe (Boletus edulis), which is the same as the Italian porcini. An English name for cepe is King bolete, an export commodity and a special forest product.
Now, the cepe and most boletes (mushrooms with tubes rather than gills) live in mutualistic symbiosis with higher plants. The mushroom provides mineral nutrients to the tree, and in return the mushroom gets sugar from the plant’s photosynthesis. Saisamorn’s research implied that this mushroom is indeed capable of forming mycorrhiza, but in the laboratory it also formed fruitbodies without a plant host! A mushroom which has the ability of selecting either a symbiosis or a parasitic or cellulose degrading life form would of course be a winner, but the ecologists claim such an organism can not exist, because the selective forces only favours specialty.
Nonetheless, our field studies imply the mango bolete exists in pure fruit orchards which do not form this type of ectomycorrhiza (we have spent many hours by the microscope studying longan roots, Dimocarpus longan, Sapindaceae, is an edible fruit). We therefore believe we have found an exception from the ecological dogma, a mushroom capable of changing between at least two life forms. Saisamorn Lumyong had explained earlier that it is very hard to find an experimental field plot because it is very hard to instruct a land owner what he can and what he can not do, especially if a study lasts over many years. Dokmai Garden offered to host a pilot field study and so in 2007 I planted many pieces of mango bolete mycelium inside Dokmai Garden.
On the 27th of August 2011 I (Eric) walked through Dokmai Garden in the afternoon and I could hardly believe my eyes when finding a massive mango bolete growing near a hedge of star apple (Chrysophyllum cainito, Sapotaceae). The weight was 128 g. To my knowledge this mushroom species had not been recorded previously from the inside or the surroundings of Dokmai Garden. Numerous forays over the years would have resulted in findings, had it been around. I was so thrilled my wife remarked I seemed happier about this mushroom than about our unborn baby, but this was just another joy. I asked the rest of the staff if they had ever seen this mushroom inside the garden before, and sure enough, they said that while we were in Sweden in June, they picked some on the other side of the star apple hedge, inside the experimental plot! NOBODY TOLD ME UNTIL NOW!? Update August 31, 2011: This morning I learnt that a Karen worker who found this mushroom in June, learnt to recognize this species from our local northern Thai worker who found it in he same place in April! That is unusually early but the rains began in March this year (normally in May). It also shows that we have failed with the rule ‘do not eat anything, show it first’. However, the workers swear they never saw his mushroom in previous years.
Well, now we have successfully grown the mango bolete in the field. I won’t bother writing a scientific publication on this pilot study. I became a gardener to avoid the paper work and the stressful fund raising and reporting at university. However, I have alerted my colleagues about this first field production ever, and it will be mentioned in future publications. Tissue samples have been taken to re-isolate the mycelium, we took photographs and measurements and we dried pieces to be deposited at Chiang Mai University. And yes, the taste is divine!
This finding shows it is possible to establish the mango bolete in the field and we know it may take four years until fruit body formation. My hypothesis is that this is primarily a saprotrophic species (no doubt of that as it readily and repeatedly forms mature and normal fruit bodies in plastic pots with peat and vermiculite and without a tree, Kumla et al. 2011). Although it can form mycorrhizal structures with Pinus kesiya, it is uncertain if they occur in nature or if they function as nutrient exchange organs. As the mycelium does not penetrate the roots of ‘host fruit trees’ I do not think it is a parasite. However, I hypothesize that the mycelium grows towards root-sucking hemipteran insects (Goncalves 1940) and enclose these and the roots. The insects suck sap from the roots, and like aphids they exudate excess carbodydrate-rich sap after picking up the very rare amino acids, and the mycelium which has wrapped the insect and the root benefits from these exudates. The insect is protected by the fungus.
Why has it only been found in one place while I planted out mycelia under many trees and even in a heap of teak saw dust? In fact, the habitat where I found it resembles very much habitats I have seen in China and Thailand, always quite open, grassy, but near a tree. The former longan orchard at Dokmai Garden has over the years grown much more dense and shady due to introductions of other trees, apparently not favourable for fruitbody production, whatever the reasons.
Thailand and China are proceeding with commercial applications. A longan or mango orchard may in the future carry two cash crops. The annual world market for cepe has been estimated at between 20 000 and 100 000 tonnes. I predict that in the future this mushroom will be an exotic specialty in the Chiang Mai restaurants. Cook it like you cook cepe. I prefer cutting it into very small pieces, frying the pieces at low heat in butter and let them simmer in cream after the water has evaporated. Serve with tagliatelle.
Do you wish to grow it yourself? In the future there will be commercial mycelia available which are already firmly established on their substrate, which you can dig down or keep in pots, but why not get fruitbodies collected in the field (they are available now)? Separate the spore producing layers from the delicious flesh, mix the spore producing tubes with water and sprinkle under your fruit trees. Spreading spores is not like planting seeds, but it may work. Is four years too long to wait? When I grew chanterelle fruitbodies for the first time in the greenhouse the age of the mycelium was about the same (Danell & Camacho 1997). Mushrooms are an overlooked dimension in a garden. Ephemeral, delicious, poisonous, colourful, wood degrading, parasitic, mutualistic, fragrant, sculptural, mysterious.
We thank ‘Karljohanstiftelsen’ for financial support.
Eric Danell & Junpol Paianusorn
The mother mycelium was derived from mango bolete fruitbodies using tissue culturing.
Danell E & Camacho F (1997) Successful cultivation of the golden chanterelle. Nature 385: 303
Goncalves CR (1940) Observacoes sobre Pseudococcus comstocki (Kuw., 1902) atacando Citrus na baixada fluminense. Rodriguesia 4: 179–263.
Kumla J, Bussaban B, Suwannarach N, Lumyong S, Danell E. (Submitted). Fruit-body Formation of an Edible Wild Ectomycorrhizal Fungus, Phlebopus portentosus without host plant.
Kumla J, Danell E, Bussaban B, Lumyong S (2011). Suitable growth conditions and nutrition factors on in vitro culture of Phlebopus portentosus (Boletales). Chiang Mai J Sci 38:156–159.