Cannabis Sex Determination: Male, Female, Hermaphrodite & DNA Testing
Cannabis is dioecious — separate male and female plants. Hermaphroditism is common and can ruin harvests.
1. Sex System
- Female (
): Produces buds with highest cannabinoid content - Male (
): Produces pollen sacs. One male can pollinate entire grow room → 30-50% cannabinoid loss - Hermaphrodite: Both male and female flowers on one plant
XY Chromosome System
XX = Female, XY = Male. Y chromosome ~500 Mb. SDR ~100 Mb (Prentout et al., 2024)
Monoecy1 Gene (2025 Discovery)
- On autosome (not X/Y)
- Mo1 mutation → XX plants produce male flowers
- Explains why feminized seeds still “herm” without stress (Prentout et al., 2025)
CsETR1 — Ethylene Receptor
- High ethylene → female expression
- STS blocks CsETR1 → female plants produce XX pollen → feminized seeds
2. Sex Identification Methods
| Method | Accuracy | Earliest Time | Cost | Best For |
|---|---|---|---|---|
| Preflower observation | 85-90% | Week 4-6 veg | Free | Small growers |
| 12/12 from seed | ~95% | Day 10-14 | Free (yield loss) | Large screening |
| PCR/DNA test | 99.5%+ | Day 5-7 | $5-15/sample | Commercial/breeding |
3. Hermaphroditism
Genetic Hermaphroditism
Mo1 mutation, unstable genetics. Remove immediately.
Stress-Induced Triggers:
- Light leaks (#1 cause)
- Temperature >30°C in flowering
- K deficiency
- Late harvest → “nanners”
- pH fluctuation >±1.0
Hormone Mechanism
Stress → ethylene drops → gibberellin rises → male flowers (survival mechanism)
4. Feminized Seeds
| Feature | STS | Colloidal Silver |
|---|---|---|
| Feminized rate | 99.7-99.9% | 95-99% |
| Sprays needed | 2-3 | 14-21 daily |
| Best for | Professional breeders | Home growers |
5. Management Strategy by Scale
| Scale | Seed Type | Testing | Notes |
|---|---|---|---|
| Personal (1-10) | Feminized | Visual preflower | Check daily week 1 flowering |
| Medium (10-50) | Fem + Regular | PCR + visual | PCR for regulars |
| Commercial (50+) | Feminized (STS) | PCR mandatory | Zero tolerance |
| Breeding | Regular | PCR + phenotype | Isolate males ≥300m |
Anti-Herm Checklist
- ✓ Check light leaks before each cycle
- ✓ Flowering temp 20-26°C, max 28°C
- ✓ Stable pH: ±0.3 hydro, ±0.5 soil
- ✓ Harvest on time
- ✓ Choose stable genetics
- ✓ Daily inspection first 2 weeks of flowering
6. Trends 2024-2026
- CRISPR Mo1 knockout for herm-free strains
- Epigenetic herm-potential testing
- Field LAMP assay: 30-min sex test without lab
- AI preflower recognition: ~92% accuracy
References
- Prentout et al. (2025). Nature Plants, 11(3), 234-248.
- Prentout et al. (2024). Y chromosome evolution in Cannabis.
3-15. Additional references available upon request. - Viet Growers Community (2015). Viet Grower Handbook.
LEGAL DISCLAIMER: Educational & scientific purposes only. Controlled Herbs Act 2025 & Ministerial Regulation B.E. 2569. PT33 required for cultivation. No recreational use promotion.
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