Contamination, Hyperhydricity, and Culture Disorders
Differentiate contamination, hyperhydricity, browning, callus overgrowth, and other culture disorders using timing and pattern.
Educational reference · evidence, sources, and limits shown below
Differentiate contamination, hyperhydricity, browning, callus overgrowth, and other culture disorders using timing and pattern.
Terms to know
- microbial contamination
- Unwanted growth or presence of bacteria, fungi, yeasts, or other microorganisms in a culture system.
- hyperhydricity
- Abnormal watery, translucent, brittle in vitro growth associated with excessive tissue hydration and altered anatomy.
- phenolic browning
- Darkening of tissue or medium associated with oxidation of phenolic compounds released after stress or injury.
- necrosis
- Localized or extensive death of plant cells or tissues.
- callus
- A mass of relatively unorganized proliferating plant cells that can form at wounds or in culture; callus is not synonymous with roots or shoots.
- vitrification
- In cryopreservation, formation of an amorphous glass-like state rather than damaging ice crystals; this meaning is distinct from the older use of vitrification as a synonym for hyperhydricity.
- latent contamination
- Contamination that is present but not immediately visible and may become apparent only after time, stress, or repeated transfer.
Core science
Contamination may be obvious as bacterial turbidity, fungal mycelium, yeast growth, discoloration, odor, or tissue collapse, but slow internal contaminants can appear after multiple transfers. Timing, location, and repeated association with a donor help identify the pathway.
Hyperhydricity is abnormal watery, translucent, brittle growth associated with excess tissue hydration and altered anatomy. It is different from cryogenic vitrification, which describes glass formation during cryopreservation.
Phenolic browning, chlorosis, necrosis, weak elongation, excessive callus, fasciated shoots, and failure to root can result from explant injury, medium, PGRs, vessel humidity, ethylene, light, temperature, subculture interval, or genotype.
Why this matters in cultivation
- Quarantine affected vessels, protect the clean area, record the first detection, and investigate donor, medium lot, operator, transfer session, vessel, and incubator patterns. Do not subculture questionable material into clean production.
Measure and record
Controlled record set
Culture ID; donor; passage; medium/vessel; symptom type; day detected; spatial/session pattern; microscopy or identification; disposal; corrective action; recurrence.
Common misconceptions
Correction: See the lesson evidence and context.
Correction: See the lesson evidence and context.
Correction: See the lesson evidence and context.
Evidence limits
Visual classification is preliminary. Microbial identity and physiological cause may require laboratory or controlled comparative work.
Related encyclopedia topics
- THC-ENC-175–177 for tissue-culture workflow and media; THC-ENC-301–340 for disease, viroid, biosecurity, sanitation, and release controls.
Source notes
- Holmes JE et al. (2021). Frontiers in Plant Science 12:732344.
- Ioannidis K et al. (2022). Plants 11:2569.
- V09-SRC-002 project pathology/sanitation control source.
This lesson summarizes the source material and its evidence limits for education. Use direct measurement, controlled comparison, and the cited sources when conditions differ or a decision carries meaningful risk.