Plant Diseases, Causal Organisms, and Diagnostic Features

Flashcards detailing various plant and crop diseases, their categories, causal organisms, and diagnostic symptoms as extracted from the lecture transcript.

What is the causal organism and key symptom of Late Blight of Potato?

Causal organism: Phytophthora infestans (Oomycete). Key symptom: Water-soaked dark lesions on leaves with white fungal growth underneath in humid conditions.

What causal organism causes Wheat Stem Rust, and what are its key symptoms?

Causal organism: Puccinia graminis. Key symptoms: Reddish-brown pustules (urediniospores) on stems and leaves, later turning black (teliospores).

What disease on Rice is caused by Magnaporthe oryzae (syn. Pyricularia oryzae)?

Rice Blast, characterized by diamond or spindle-shaped lesions with gray centers and dark brown margins on leaves.

Which fungal disease affects cereal crops (Wheat, Barley, Rye) causing white to grayish powdery fungal growth on leaf surfaces?

Powdery Mildew, caused by Blumeria graminis (or Erysiphe spp.).

What key diagnostic features characterize Apple Scab caused by Venturia inaequalis?

Olive-green to black velvety spots on leaves and scabby, cracked lesions on fruit.

What is the causal organism and primary symptom of Corn Smut?

Causal organism: Ustilago maydis. Key symptom: Large, fleshy galls replacing kernels or ears, filled with black powdery spores.

What symptoms are indicative of Panama Disease (Fusarium Wilt) in Bananas?

Yellowing of older leaves, splitting of pseudostem base, and vascular discoloration, caused by Fusarium oxysporum f. sp. cubense.

How do Powdery Mildew of Grape and Downy Mildew of Grape differ in symptoms and causal organisms?

Powdery Mildew of Grape (Erysiphe necator) causes white powdery patches on leaves, shoots, and clusters with potential berry splitting. Downy Mildew of Grape (Plasmopara viticola) causes yellow 'oil-spot' lesions on upper leaf surfaces and white downy growth underneath.

What are the key symptoms and causal organism of Soybean Rust?

Causal organism: Phakopsora pachyrhizi. Key symptoms: Tan to dark brown lesions on leaves containing small raised pustules releasing tan spores.

What bacterial disease affects Apple / Pear causing blossoms, shoots, and branches to turn black as if scorched by fire?

Fire Blight, caused by Erwinia amylovora (which also exhibits bacterial ooze).

What diagnostic features distinguish Bacterial Blight of Rice caused by Xanthomonas oryzae pv. oryzae?

Water-soaked stripes on leaves turning yellow-white, with milky bacterial strands in morning.

What key symptoms characterize Bacterial Wilt caused by Ralstonia solanacearum?

Rapid wilting of the plant without yellowing, and a brown vascular ring oozing white slime.

What is the causal organism and key symptom of Citrus Canker?

Causal organism: Xanthomonas citri. Key symptom: Raised, corky, blister-like lesions surrounded by a yellow halo on leaves, fruit, and twigs.

Which bacterial disease in Crucifers produces V-shaped chlorotic to necrotic lesions extending from leaf margins with black veins?

Black Rot of Crucifers, caused by Xanthomonas campestris pv. campestris.

What is the key symptom of Tobacco Mosaic Virus (TMV)?

Mottled mosaic pattern of light and dark green areas on leaves, along with leaf distortion.

What symptoms are produced by Potato Leaf Roll Virus (PLRV) on potatoes?

Upward rolling of lower leaves, leathery texture, and stunted, pale yellow plants.

What viral disease affects Cassava, causing severe leaf distortion, chlorosis, and stunted growth?

Cassava Mosaic Disease, caused by Cassava mosaic begomoviruses (CMV).

What diagnostic symptoms characterize Tomato Yellow Leaf Curl Virus (TYLCV)?

Upward cupping and yellowing of leaf margins, stunted growth, and flower drop.

What are the symptoms and causal agent of Barley Yellow Dwarf in cereal crops?

Causal agent: Barley yellow dwarf virus (BYDV). Key symptoms: Bright yellow or purple discoloration of leaf tips, severe stunting, and reduced tillering.

What key diagnostic features identify Root-Knot Nematode Infestation (Meloidogyne spp.)?

Distinct galls or swellings ('knots') on roots, stunting, and nutrient deficiency symptoms.

Which nematode diseases affect Potato and Soybean respectively, and what are their specific causal organisms?

Potato Cyst Nematode: Globodera rostochiensis / Globodera pallida. Soybean Cyst Nematode (SCN): Heterodera glycines.

What is Damping-off, what causes it, and what are its symptoms?

Damping-off (caused by Pythium spp. or Rhizoctonia solani) is an infestation where seeds rot before emergence or seedlings collapse and rot at the soil line.

What are the key symptoms and causal organism of Fusarium Head Blight (Scab) in Wheat and Barley?

Causal organism: Fusarium graminearum. Key symptoms: Premature bleaching of wheat spikelets (whiteheads) with pinkish spore masses on glumes.