Category: Advanced Plant Pathology

Fungi as plant pathogens Fungi cause rusts, smuts, mildews, rots, and wilts. They spread by spores via wind, water splash, insects, or contaminated seed. Field symptoms vs signs Symptoms are plant responses (yellowing, necrosis). Signs are pathogen structures (mold growth, rust pustules, concentric rings). Diagnostic workflow Map distribution — random vs row pattern suggests soil-borne…

Bacterial pathogens Bacteria enter through wounds, hydathodes, or natural openings. Water-soaked lesions that may turn necrotic are typical. Yellow halos often surround spots. Confirmation methods Streaming bacterial ooze from cut lesion in water. Gram stain of exudate under microscope. Isolation on selective media in lab. Viral pathogens Viruses require living cells; they cannot be cultured…

Beyond single-spray solutions IDM combines genetics, agronomy, and chemistry to keep disease below economic injury level — not elimination of all pathogens. Hierarchy of controls Host resistance — plant resistant or tolerant cultivars. Cultural — rotation, sanitation, spacing for airflow. Biological — antagonistic microbes (e.g., Bacillus spp.). Chemical — fungicides timed to infection periods. Monitoring…

Plant-parasitic nematodes Microscopic roundworms that feed on roots, causing knots (Meloidogyne), cysts (Heterodera), or lesions. Above-ground symptoms mimic nutrient deficiency or drought. Soil sampling Collect soil from root zone at 15–30 cm depth. Send to diagnostic lab for extraction and counting. Population thresholds vary by crop. Other soil-borne threats Phytophthora — oomycete causing root rot…

Harvest to consumer Pathogens and physiological disorders continue after harvest. Soft rots, gray mold (Botrytis), and anthracnose affect fruits during storage and transport. Factors that accelerate decay Mechanical injury during harvest High humidity without ventilation Ethylene from neighboring rotting produce Chilling injury on sensitive tropical fruits Best practices Cool product quickly (hydrocooling), maintain cold chain,…

Resistance types Vertical resistance (R-gene) is strong but often overcome when pathogen evolves. Horizontal resistance is partial but broader and more durable. Breeding pipeline Identify resistant donors, cross with elite lines, screen progeny with controlled inoculation or natural field exposure, and backcross to recover agronomic traits. Marker-assisted selection DNA markers linked to resistance genes speed…