Last week, three samples of wood-decaying fungi were collected, but because a closely related species of the deadly amanita was mistakenly treated as an edible fungus for research, not only was a week of cultivation time wasted, but the entire strain library was almost contaminated. This is the recent frustration of Xiao Li from a university fungal research laboratory. In the field of fungal research, such 'identification errors' are not uncommon. According to statistical data released by the Journal of Mycosystema in 2024, approximately 42% of beginners in fungal research experience experimental data distortion due to identification bias, while professional researchers also have a 15% probability of misjudgment when handling unknown fungal species. With over 1.2 million species discovered globally, fungi exhibit enormous diversity in morphology and habits. Accurate fungal identification is both the starting point of research and the key to risk avoidance. This article will provide fungal researchers with a systematic and operational identification method to help you overcome the difficulty of 'fungal recognition'.
Before starting identification, establishing the correct conceptual framework can help you avoid detours. Many identification errors stem from misunderstandings about the basic attributes of fungi.
Fungi belong to an independent 'Fungi Kingdom.' Their cell structure lacks chlorophyll and cannot perform photosynthesis, which is fundamentally different from plants; at the same time, they obtain nutrients by absorbing organic matter, which differs from animals. This characteristic determines that fungal identification cannot rely solely on 'appearance' but must also consider their nutritional sources, growth environments, and other factors. For example, white mycelium growing on humus may be Trichoderma, while that growing on the phloem of living trees may be parasitic Phytophthora.
Fungal morphology changes with growth stages and environmental conditions, which is 'same fungus, different appearance.' For example, Cordyceps sinensis appears as an insect body in winter and develops fruiting bodies in summer; 'different fungi, same appearance' refers to different fungal species having highly similar morphology at a certain stage. The most typical example is the deadly amanita and the edible white amanita, which are difficult to distinguish with the naked eye alone and require professional methods.
A single characteristic cannot accurately identify fungi. Professional identification logic combines morphological characteristics, growth environments, and molecular detection. The 'Triple Verification Method' proposed by the Mycological Society of America has become an industry standard: first preliminary classification through morphology, then narrowing the range by combining growth environments, and finally confirming species using molecular methods.
This section is the focus of this article, covering full-process identification techniques from field collection to laboratory analysis, with each method including practical steps and precautions.
Macroscopic observation targets fungal fruiting bodies (such as mushroom caps and stems) or colonies (such as mycelial aggregates on culture media), which is the first step in identification. It is simple to operate but requires meticulous attention. Practical steps: 1. Record overall morphology: For agaric fungi, observe cap shape (round, bell-shaped, funnel-shaped), diameter, color (whether there are color changes, such as bolete turning blue after injury); stem length, thickness, presence of annulus or volva. 2. Observe accessory features: Check the color and arrangement of gills (thin sheets under the cap) or tubes. For example, shiitake gills are white, turning light brown when mature, and are perpendicular to the stem. 3. Test key reactions: Some fungi have specific reactions. For example, breaking the stem of fresh Lactarius fungi and observing whether there is latex exudation and color changes in the latex is an important basis for distinguishing Lactarius species. Precautions: Macroscopic observation should be conducted in fresh condition, as fungal fruiting bodies undergo significant morphological changes after drying, which affects judgment.
Fungi have strong specificity for growth environments. Combining environmental information can significantly improve identification efficiency. According to research, approximately 70% of fungi have preferences for hosts or growth substrates. Key tracing points: •Growth substrate: Whether it is saprophytic (growing on dead wood, fallen leaves, humus), parasitic (growing in living animals and plants), or symbiotic (such as forming mycorrhizae with trees). For example, matsutake only forms symbiotic relationships with trees like Japanese red pine and Yunnan pine, and will not grow in pure grasslands. •Climate and region: Different fungi have specific growth temperatures, humidity, and regional distributions. For example, Cordyceps sinensis is only distributed in alpine meadows at altitudes of 3000-5000 meters on the Qinghai-Tibet Plateau. •Growth season: Most fungi have obvious peak growth seasons. For example, oyster mushrooms grow vigorously in spring and autumn but appear less frequently in summer.
When macroscopic characteristics cannot distinguish fungi, observing fungal spores, mycelia, and other microscopic structures with a microscope is one of the core methods of professional identification. Practical steps: 1. Sample preparation: Take a small amount of fruiting body tissue or mycelium, place it on a glass slide, add 1-2 drops of clear water or lactophenol cotton blue stain (to make structures clearer), cover with a coverslip, and gently press to disperse the sample. 2. Microscope observation: First use low magnification (10×) to locate target structures, then switch to high magnification (40×) for detailed observation. Focus on spore shape (round, elliptical, spindle-shaped), size, color, and whether mycelia have septa or clamp connections (important characteristics of basidiomycetes). 3. Record data: Measure spore size (randomly measure 20 spores and take the average), record mycelial diameter and characteristics. These data are key to distinguishing closely related species. For example, Beauveria bassiana spores are spherical with a diameter of 2-3 micrometers, while Metarhizium anisopliae spores are long elliptical with a diameter of 3-5 micrometers.
Fungi have species-specific physiological and biochemical characteristics. By testing their ability to utilize different carbon and nitrogen sources, or detecting enzymes and metabolites they produce, accurate identification can be achieved. Common test items: •Carbon source utilization test: Inoculate fungi onto culture media containing different carbon sources (such as glucose, sucrose, cellulose) and observe their growth. For example, yeasts can grow using glucose, but some species cannot utilize lactose. •Enzyme activity detection: Detect whether fungi produce enzymes such as amylase or cellulase through specific culture media. For example, Trichoderma produces large amounts of cellulase and will form obvious transparent zones on cellulose-containing culture media. •Pigment production test: Some fungi produce specific pigments. For example, Penicillium chrysogenum produces yellow-green pigments, which is an important identification characteristic.
For closely related species or fungi that are difficult to distinguish morphologically, molecular biology methods are currently the most reliable identification means. The core principle is to detect specific gene fragments of fungi (such as ITS sequences) and compare them with known sequences in databases to confirm species. Practical process (commonly used in laboratories): 1. DNA extraction: Extract genomic DNA from fungal samples using CTAB method or commercial kits. 2. PCR amplification: Amplify target gene fragments using universal ITS primers (such as ITS1 and ITS4). 3. Sequence determination: Send amplified products to sequencing companies for sequencing to obtain gene sequences. 4. Comparative analysis: Perform BLAST comparison of obtained sequences in databases such as NCBI (National Center for Biotechnology Information). Sequences with similarity above 97% can be preliminarily determined as the same species. According to reports from the Journal of Microbiology, molecular biology methods have improved fungal identification accuracy from 75% in traditional methods to over 99%, making them indispensable in current scientific research.
In addition to the above core methods, using professional tools can make identification work more efficient. •Identification manuals and atlases: Authoritative materials such as 'Chinese Large Fungi Atlas' and 'Fungal Identification Manual' contain a large number of high-definition images and characteristic descriptions, suitable for beginners to consult. •Mobile APPs: APPs such as 'Fungal Identification' and 'Mushroom Identification' can perform preliminary identification by photographing fruiting bodies and can be used as rapid screening tools during field collection, but results need further verification. •Professional databases: In addition to NCBI, there is also the 'Chinese Fungi Database' from the Institute of Microbiology, Chinese Academy of Sciences, which contains detailed information on many native Chinese fungi.
Answer: There is no absolute 'quick distinction technique,' but two principles can be followed: First, 'never collect what you don't recognize,' especially fungi with bright colors (such as red, yellow), special odors (such as fishy smell), or color changes after injury, which require extra caution; second, use the 'exclusion method' by first recording the growth environment. If growing near poisonous plants or on corpses, they are likely toxic. Final confirmation requires combining laboratory microscopic observation and molecular detection.
Answer: Abnormal colony morphology may be caused by changes in culture conditions (temperature, humidity, culture medium composition). At this time, culture conditions should first be adjusted to observe whether the colony morphology returns to normal; if still abnormal, a combination of 'microscopic structure observation + molecular detection' can be used to confirm the species through spore and mycelial characteristics and gene sequences, avoiding being misled by abnormal morphology.
Answer: Similarity between 95%-97% indicates that the fungus may be a closely related species or a new species of a known species. At this time, comprehensive judgment is needed by combining morphological characteristics and physiological and biochemical characteristics: if morphological and physiological characteristics are highly consistent with known species, it may be different geographic populations of the same species; if there are obvious differences, it may be a new species requiring further taxonomic research.
Answer: It is recommended to start with common fungi with obvious morphological characteristics, such as shiitake, oyster mushrooms, and enoki mushrooms, which are artificially cultivated fungi with stable morphology and rich materials, making it easy to master identification points. After mastering the basics, gradually transition to complex types such as saprophytic fungi and symbiotic fungi in the wild.
Accurate fungal identification is the foundation of fungal research. Its core lies in 'multi-dimensional verification'—neither relying solely on naked-eye judgment nor over-relying on a single technology. From preliminary screening of macroscopic morphology, to tracing growth environments, to observing microscopic structures and ultimate verification through molecular biology, this systematic method can help you avoid identification risks and improve research efficiency.
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