- Phytoplasma are wall less bacteria like organisms
- They belong to the class Mollicutes
- They lack a rigid cell wall and are pleomorphic in shape
- They are obligate parasites and cannot survive outside host organisms
- They infect plant phloem tissue and depend entirely on the host for nutrients
Key Characteristics
- Absence of cell wall makes them resistant to antibiotics like penicillin
- Extremely small genome with limited metabolic capacity
- Confined to phloem tissues of plants
- Cannot be cultured in artificial laboratory media
- Multiply by binary fission
Transmission
- Transmitted mainly by phloem feeding insect vectors
- Common vectors include
- Leafhoppers
- Planthoppers
- Psyllids
- Transmission is persistent and propagative
- Once infected, the insect remains a carrier for life
Symptoms in Plants
- Little leaf formation
- Yellowing of leaves
- Witches broom appearance due to excessive branching
- Phyllody where floral organs are converted into leaf like structures
- Stunted growth and reduced yield
- Decline and eventual death in severe infections
Important Phytoplasma Diseases
- Little leaf disease of brinjal
- Grassy shoot disease of sugarcane
- Sandal spike disease
- Sesame phyllody
- Witches broom disease in legumes and ornamentals
Diagnosis
- Cannot be cultured, so diagnosis relies on
- PCR based molecular techniques
- DNA hybridisation
- Fluorescent microscopy
- Electron microscopy used for visual confirmation in research
Control and Management
- No direct curative treatment once plant is infected
- Management strategies include
- Removal and destruction of infected plants
- Control of insect vectors using integrated pest management
- Use of disease free planting material
- Crop rotation and field sanitation
- Antibiotics like tetracycline may suppress symptoms but are not practical for field use
Significance in Agriculture
- Cause heavy yield losses in economically important crops
- Difficult to manage due to lack of curative treatment
- Major concern in tropical and subtropical agriculture
