Is there any relationship between fruiting depth, weight and maturity for black truffle?

The last months the CITA research center, in Spain, has published two great papers analyzing the truffle fruit bodies from two seasons in different soil types and for the first time inside spanish wells with peat moss.

This is the second paper just published

Lack of Linkages among Fruiting Depth, Weight, and Maturity in Irrigated Truffle Fungi Marks the Complexity of Relationships among Morphogenetic Stages

the authors wanted to check if in Fruit Body (FB) clusters, the weight of the largest FB would show a negative relationship with the weight of the remaining FBs, due to the local resource depletion or inhibition mechanisms hypothesized by other authors; and if the differences among soils and with substrate would affect relationships among FB development characters, since soil properties and spanish wells are able to influence these characters.

Results for the truffles that fruit alone are:

(i) fruiting depth did not show a significant relationship with any other character,

(ii) FB weight showed a strong negative relationship with the shape index (i.e., bigger FBs having more irregular, less rounded shapes), and 

(iii) the Harvest Date showed a strong positive relationship with spore maturity, that initially looks obvious. The Harvest Date showed a significant and negative relationship with FB weight in the substrate, and 2 kind of soils, that could be related to the loss of weight during winter. Note February is one of the driest months in Spain, and this is why several growers water during winter. 

As an example, in our own farm this winter we have already irrigated 6 times this harvest season since late November (9 times last year)

And the results for the truffles that fruit in clusters are:

i) fruiting depth did not show a significant relationship with any other character,

(ii) the weight of the largest FB in a cluster showed a strong positive relationship with the combined weight of all the other FBs in the cluster, and 

(iii) the Harvest Date did not show a significant relationship with the weight of the largest FB in the dig.

In the substrate of the spanish wells and one of the soils, the weight of the largest FB in the cluster showed a strong negative relationship with its shape index (again larger truffles get the worst shape) . In the substrate the Harvest Date showed a significant and negative relationship with the weight of the remaining FBs in the cluster, so again we have to mind that peat moss dries up more than surrounding soil, and as growers, we better measure with probes and water accordingly.

On the other hand, when we check these following figures, looks like there is a better weight in the largest truffle in the cluster at 10-20cm, that is where we normally want them to fruit when we create the spanish wells with substrate:

shape index is better in the top shallow truffles, guess that compaction is lower there:

Conclusions:

• The soil depth at which truffle FBs grew did not show any causal link with FB weight, shape, or spore maturity for any of the soil or dig typologies analyzed. This suggests that, under the experimental conditions, weight and maturity do not depend on FB location throughout the soil profile.

• In that experimental site the existing ranges in microclimatic variables did not trigger changes in weight or maturity throughout the soil profile for any soil typology.
• Bigger FBs showing more irregular, less rounded shapes.
• No causal link between FB maturity and weight was found.
• A positive relationship between the weight of the largest FB and the weight of the remaining FBs was clear among the FB clusters of all the analysed soils. The relationship between these development characters is very strong in the substrate, which is much looser than the bulk soil.

This was not expected. Authors had initially hypothesized that local resource depletion would trigger compensating mechanisms between FB survival and FB size in a dig, in consonance with the fact that, before summer, the density of T. melanosporum FBs (still immature) in the soil is much higher than the density of ripe FBs localized by dogs in the fruiting season.

Again, lots of interesting data. Congrats to the research team.

All the best!

Marcos morcillo