Stay tuned!
Subscribe to the newsletter to stay informed about our new training courses, our new products and our latest tips for growing your truffle farm!
That’s a good question. What truffle farmer hasn’t dreamed of tracking their harvest from the moment the truffles are born? We’re not quite there yet, but a study published in 2014 by Giovanni Pacioni’s team at the University of L’Aquila in Italy (Mycorrhiza, 2014) has begun to answer this question.
This study presents the main results of research into the birth and development of truffles of the species Tuber melanosporum. in a truffle field. The researchers used two instrumental monitoring methods to conduct this investigation:
The main objective was to gain a better understanding of the moment when the mycelium of T. melanosporum transitions from the vegetative phase to the reproductive phase and to find a non-destructive tool for monitoring the subsequent development of fruiting bodies.
One of the major findings of this study is the identification of CO2 production in the soil as a reliable parameter for indicating the “birth” of truffle primordia.. Researchers observed that the primordia of T. melanosporum seem to form when mycelial activity is intense, undergoes water stress, and then resumes. More specifically, they found that approximately 6 to 18 days after metabolic activity resumed, they could harvest primordia. This suggests that changes in the metabolic processes of truffle mycelium, which can be measured by the flow of CO2 emitted from the soil, are closely linked to the triggering of truffle development. A decrease in activity, reflected in lower CO2 concentrations due to water stress, followed by a rapid increase in CO2 with the arrival of rain and warmer soil temperatures (around 20°C), were conditions associated with the development of fruiting primordia. The study revealed that the induction of primordia T. melanosporum is a recurring event, potentially predictable using a model based primarily on CO2 concentrations in the soil. Researchers continued to collect truffle primordia based solely on changes in this parameter, highlighting its importance.
The study also highlighted a difference in metabolic activity, measured by CO2 concentration, between the burned area (“pianello” or “burned”), characteristic of the presence of truffles, and the surrounding area. The CO2 sensor located inside the burned area consistently recorded absolute CO2 flux values almost three times higher than those recorded by the sensor located outside this area.
This difference was particularly pronounced from the second half of April to the end of June and again from early September to December, suggesting that metabolic activity is significantly higher in the area colonized by the mycelium of T. melanosporum.. Although temporal variations in soil CO2 have been considered an expression of the metabolic activity of the mycelium of T. melanosporum, researchers acknowledged that these variations could also coincide with natural phenomena linked to increases in soil temperature and humidity. However, the substantial difference in CO2 flux between burned and unburned areas suggests a significant contribution from truffles.
It is interesting to note that the study found that CO2 trends did not show a simple statistical correlation with soil moisture and temperature values. This suggests that although temperature (daily average above 20°C and below 12°C) and soil moisture (below 35-40%) appear to be critical and may independently affect soil metabolic activity and CO2 flux, the relationship is complex. The duration of these unfavorable conditions also appeared to negatively influence CO2 production. These observations support previous research suggesting the independence of soil water content and temperature in controlling soil respiration.
The second instrumental method used was ground-penetrating radar (GPR)., which has been tested for its ability to non-destructively monitor the development and growth of truffle fruiting bodies in the soil. The results demonstrated that GPR could identify individual truffles in the soil once they had reached a size of at least 6 mm in diameter and could be used to track their growth in volume and diameter over time. GPR surveys conducted at different times revealed that several generations of fruiting bodies could develop or degenerate within a few weeks, highlighting the dynamic nature of truffle development underground. By subtracting the signals present in successive radargrams, the researchers attempted to link the GPR data to the assessment of the number of fruiting bodies.
However, the study also identified challenges and technical limitations associated with the GPR technique.. The interface between the antenna and the often uneven ground could generate distortions in the radar signal, potentially leading to the creation of false targets. In addition, the high-frequency bowtie antenna used had a sensitivity that varied depending on the orientation of the truffle growth relative to the polarization of the antenna, which could result in distorted and oversized radargrams compared to the actual dimensions of the truffles. As a result, the signals detected by the GPR were not always directly and accurately related to the actual size of the truffles.
By comparing truffle production to that of other fungi such as Basidiomycetes, the study noted similarities in that the conditions favoring mycelium growth and fruiting body development appear to be distinct, often involving a change in environmental conditions. The observed trend in CO2 concentration supports this idea: increases could promote mycelium growth, while decreases could stimulate the formation of fruiting body embryos. Similar to the “flushes” observed in cultivated mushrooms, the induction and production of fruiting bodies in T. melanosporum seem to occur in successive periods. However, the time required for full maturation differs considerably, T. melanosporum requires several months, estimated at around 5 months from induction to maturation. according to the study data. This timeframe suggests that truffle harvests taking place from January to March in central Italy are likely the result of inductions occurring in late fall.
The researchers concluded that these two monitoring systems, CO₂ sensors and GPR, show promise for improving understanding of the production and development processes of T. melanosporum in relation to environmental factors.. Their use could potentially improve the management of truffle farms. The study also adds to our understanding of the nutrition mode of T. melanosporum, reinforcing the fundamental role of host plants in transferring nutrients to the ectomycorrhiza-mycelium-fruiting body complex, thereby ruling out the possibility of a significant saprotrophic phase.
In summary, this research has provided valuable information on the phenology of T. melanosporum truffles by:
Subscribe to the newsletter to stay informed about our new training courses, our new products and our latest tips for growing your truffle farm!
