Hypothesis
The lifecycle of a mycorrhizal species will result in fructification earlier if it is within a pocket mycorrhizae, eg, a mycorrhizae that is only active in a really small area. If the entire 'mycorrhizae' is just in a jar, the conditions of fruiting will obviously obtain earlier than if you have a plantation of 20 trees spanning a large area.
Background
This study found the fructification of chantarelles on 16-month-old saplings in a greenhouse. while other sources generally estimate a time of 3-7 years from planting of inoculated saplings to fruiting. So the chantarelles fruited more quickly in an isolated environment, likely because the entire span of the 'mycorrhizae' the mushroom had to deal with was relatively small.
In the growth of truffles, commercialization has begun in many areas, but one downside to the investment is the long time before fructification from introduction of the spores, sometimes up to 10-15 years as the trees mature. An American company, Burwell farms, recently boasted of finding truffles 2.5 years after planting one of its orchards, which may be a record.
Experiment description
To see whether fructification of a tuber sp. (for example T. Melanosporum) can be achieved in an even shorter time than was found by Burwell farms, if the only mycorrhizae available at all was in a small enclosed area - such as a terrarium or greenhouse. The essential idea would be a 'pocket mycorrhizae'. The simplest means of this would be simply a jar with a plant growing in it, relatively isolated from the plants outside.
Methods and materials
A fruiting body of a truffle sp. (prob. T. Melanosporum, I would like to find a PNW native truffle but they are harder to source for me) will be used to inoculate a small jar terrarium in which a tree is living. Half of the truffle will be ground and turned into a slurry so that the spores can be distributed around the soil; other parts of the truffle will be cut up and left in the soil in larger pieces, to potentially act as a longer-lasting and more stable inoculant. (See a note at the bottom on what I've researched about the fruiting of the Tuber sp. for justification of this technique).
The plant could either be grown first from acorn or from a cutting. I think growing it from acorn after truffles were already introduced to the soil may be the most sure method because the plant would be introduced to the fungus from its start of life without the ability of any other competing species to get a foothold. Additionally, the acorn can be soaked in water with truffle spores before being introduced to soil that also has truffle spores in it.
Here is what I'm not entirely sure of yet, though: What is the best method to create an isolated mycorrhizae? I could see maybe a few potential ways to do it. One would be to treat it as a closed terrarium, eg a sealed jar - these are hard to predict, but often the plant provides enough oxygen to keep living and even sustaining an insect population. However, I fear that this method will create a less varied and vibrant insect community because of the 'stuffy air' created by sealing the jar - further that the plant would not be as healthy. Also, it may be that fresh air exchange is a crucial component of the growth of truffles, as it is for the basidiomycetes mushrooms. I could conduct this experiment in a greenhouse, as the Oregon State researchers did with chantrelles, and use air circulators and other things used in professional greenhouses; but I don't have one currently, and I imagine that fruiting within a whole greenhouse would take more time than in an even more isolated area, one jar.
My current plan is one of the following (haven't decided):
A. in a small jar mycorrhizae, isolation is achieved by covering the environment with breathable foam, as is used to store fruit flies - foam that allows gas exchange but does not allow insects to escape or enter from outside. (One can consider a completely sealed jar terrarium a secondary example of A.)
B. a small jar mycorrhizae that is open to the air entirely, perhaps outside near larger trees. In this case insects can come and go freely from the jar, but unfortunately may bring spores from other competing mycorrhizae species from trees around.
Method A achieves superior isolation, while still allowing gas exchange. However, no more insects would be able to gravitate towards the mycorrhizae other than those already living in the soil at the time. Insects, however, are probably important in some respects given how they spread the truffle mycelium, would help break down the truffles left in the soil and may help the fructification process.
Method B still achieves some measure of isolation - however, would be exposed to the rain as well as insects that live primarily in trees around, which surely have other very healthy mycorrhizae in them. According to my research, soil surrounding mycorrhizal trees can be filled with condia from them - outside insects may bring these conidia to the small jar, creating competition.
But is it possible competition wouldn't be bad? As long as the mycorrhizae is established firmly in the jar, perhaps if it is opened the conidia from outside sources wouldn't be able to do much. Perhaps the outside competition exposure might trigger fruiting. However, with the achievement of fruiting faster in a greenhouse with chantrelles than outside of one, isolation probably needs to be maintained to some degree or else the mycorrhizae won't be able to maintain itself against so many competing outside forces.
Also, method B will make it hard for me to handle when it rains - the jar will overflow with too much water. I'll have to pour some out out, which will obviously introduce some of the conidia from this jar to the ground around. Would this hurt the 'isolation' I am looking for in my mycorrhizae, to result in fruiting later?
A note on fruiting of Tuber sp.
Looking at these two studies on this subject, 1, 2, one can reach a similar conclusion: the mycelium of a tuber sp. starts off with high diversity as sexual ascospores fruit into one of the two sexes (we can call them m or f). Eventually, the mycorrhizae becomes all 'female' sex, which seems to coincidence with the maturation of it. In studies on plantations, eventually all the mycorrhizae found in all the trees becomes one sex, hence the mycelium all becomes the 'mother' - this process being noted to take several years.
This then has resulted in something described in research as 'the mystery of truffle parentage' or 'the missing father', eg where the other sex comes from in order to produce fruits. The theory seems to be that the 'father' is represented by the spores distributed from the fruiting bodies by animals, perhaps sometimes from a slightly different truffle plantation (eg birds who come from one mycorrhizae to another), other times from fruiting bodies produced by the same plantation. This creates a 'spore bank' within the soil. The ascospores are eaten by an animal and then travel through the animal poop as new inoculating material around the trees, potentially a fruiting trigger. The stable, established mycorrhizae being the mother, the random generic material introduced from many sources acts as 'father'.
The relevance for this study is that it shows the mycelium of all inoculated plants talks extensively to each other and gets on the same 'page' sexually as the mycelium matures. Therefore, with a smaller amount of mycelium to all mature as the 'mother', fructification may happen quicker - so if the only truffle inoculated trees are in a greenhouse with the spores only being distributed by insects, as opposed to having to rely on larger animals, maturation may take substantially less time.
Now, how could this 'father', found from ascospore distribution, be replicable in a pocket mycorrhizae? The answer would be to do in your experiment what animals in nature do: to distribute ascospores throughout the medium. One could grind up a truffle into a slurry and pour that water in the medium, littering ascospores throughout the medium, which could be enough of a reserve in the soil to trigger fructification.
The method discussed earlier I think takes account of this unique aspect of truffle physiology to help earlier fruiting. That method was to leave big pieces of a truffle as well as to use a spore slurry. The big pieces that stay intact will create a stable mycelial culture, which will soon act as the mother; the distributed ascospores will create genetic diversity, resulting in more interactions between father and mother and, hopefully, eventual fruiting. In this setting, insects will probably be essential - ascospores can probably be moved around by fungus gnats, mites, spiders, etc in the medium, and that might be essential to any success. It seems as though truffle plantations favor certain mites, probably those that form symbiotic relationships to it (see this study).
What would the effect be of an open jar around trees? Well if all the trees were inoculated with truffles, I think the mycorrhizae of the jar would 'talk' to the tree mycorrhizae (through conidia and ascospores distributed by insects, etc), and it may take much longer for fructification because it is no longer isolated. Because the mychorhizae would then encompass the whole area surrounding the trees too, I think it would take much longer for all these truffle-inoculated plants to get the same mycelial sex as the 'mother'; thus, my theory is that fructification would take longer in an open jar around truffle trees than it would be if the jar was more isolated. (Fructification may still be faster in an open jar than in a planted inoculated plant). But there may be an alternative - what if an open jar near truffle trees is exposed to more spores in the 'spore bank', and hence may get a fruiting trigger faster?
But what if there is an open jar next to trees that haven't been inoculated with truffles? Would it perhaps fruit faster with competitive pressures? Slower because there are conidia from a higher range of species being distributed to the medium, making it harder for the truffles to take control? I am not sure.
Final thoughts
I will start this experiment within the next few weeks. I will have to obtain materials (acorns, truffles) and I am trying to decide between methods, either A (a closed jar or jar sealed off with breathable foam) or B (jar open to the air). The place where I get fresh truffles doesn't have any in yet. A greenhouse with a good ventilation system may be ideal, but I do not have the materials for that as of yet - I could make one. However, perhaps a 'grow tent' similar to how cannabis is sometimes grown, with good ventilation, would be a good middle ground in terms of maintaining a mycorrhizae while keeping it isolated, but still allowing good air exchange and potentially a healthy insect population. There are a lot of considerations.
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