Give the name of the causal organism, symptoms and control measures of any four important crop diseases caused respectively by a bacterium

Bacterial Crop Diseases: Causal Organism, Symptoms & Control Measures

Here's a detailed look at four important bacterial crop diseases:

1. Bacterial Blight of Rice (Xanthomonas oryzae pv. oryzae)

• Causal Organism: Xanthomonas oryzae pv. oryzae
• Symptoms: Initially, water-soaked lesions appear on the leaves, which later turn brown and necrotic. A yellowish halo often surrounds the lesions. The disease can also affect the leaf sheath and grain, causing sterility. Creeping blight, a severe form, manifests as a yellowish-brown discoloration spreading across the leaf.
• Control Measures:
  • Use of disease-resistant varieties (e.g., varieties with the Xa21 gene).
  • Seed treatment with bactericides like copper oxychloride or streptomycin.
  • Crop rotation with non-host crops.
  • Proper drainage to avoid waterlogging.
  • Application of bio-control agents like Pseudomonas fluorescens.

2. Bacterial Soft Rot of Vegetables (Erwinia carotovora subsp. carotovora)

• Causal Organism: Erwinia carotovora subsp. carotovora
• Symptoms: Characterized by a soft, watery, and foul-smelling rot of tissues, particularly in potatoes, carrots, and other root vegetables. The affected tissues become discolored and easily disintegrate. Often enters through wounds caused by insects or mechanical damage.
• Control Measures:
  • Avoid mechanical injuries during harvesting and handling.
  • Proper storage at low temperatures.
  • Use of disease-free seeds and planting material.
  • Sanitation – removing and destroying infected plant debris.
  • Application of bactericides like copper sulfate.

3. Citrus Canker (Xanthomonas citri)

• Causal Organism: Xanthomonas citri
• Symptoms: Causes raised, corky lesions on leaves, stems, and fruits. These lesions are often surrounded by a yellow halo. Severe infections can lead to defoliation and fruit drop.
• Control Measures:
  • Use of disease-free planting material.
  • Copper-based sprays as a preventative measure.
  • Pruning and destruction of infected branches and fruits.
  • Quarantine measures to prevent the spread of the disease.
  • Biological control using antagonistic bacteria.

4. Common Blight of Beans (Xanthomonas axonopodis pv. phaseoli)

• Causal Organism: Xanthomonas axonopodis pv. phaseoli
• Symptoms: Causes brown, angular leaf spots with a yellow halo. The spots can coalesce, leading to leaf blight and defoliation. Stem lesions can also occur, causing girdling and plant death. Seeds may also be infected.
• Control Measures:
  • Use of disease-resistant varieties.
  • Seed treatment with bactericides.
  • Crop rotation with non-leguminous crops.
  • Avoiding overhead irrigation.
  • Sanitation – removing and destroying infected plant debris.

The following table summarizes the information presented above:

Disease	Causal Organism	Key Symptoms	Control Measures
Bacterial Blight of Rice	Xanthomonas oryzae pv. oryzae	Water-soaked lesions, yellow halo, creeping blight	Resistant varieties, seed treatment, crop rotation, drainage
Bacterial Soft Rot	Erwinia carotovora subsp. carotovora	Soft, watery, foul-smelling rot	Avoid injury, low-temp storage, disease-free seeds, sanitation
Citrus Canker	Xanthomonas citri	Raised, corky lesions with yellow halo	Disease-free material, copper sprays, pruning, quarantine
Common Blight of Beans	Xanthomonas axonopodis pv. phaseoli	Brown angular leaf spots, yellow halo, defoliation	Resistant varieties, seed treatment, crop rotation, avoid overhead irrigation