Which of the following plant disease(s) are caused by bacteria ? (a) Rust of…

Plant diseases are classified by the type of pathogen that causes them — fungi, bacteria, or viruses — and each pathogen group produces disease through a characteristic causal organism: rust fungi cause fungal rusts, Xanthomonas/Pseudomonas species cause bacterial cankers and blights, and insect-transmitted geminiviruses (begomoviruses) cause viral mosaics.

• Rust of wheat is caused by the fungus Puccinia graminis (a rust fungus) — a fungal disease, not bacterial.

• Citrus canker is caused by the bacterium Xanthomonas citri (Xanthomonas axonopodis pv. citri) — a bacterial disease.

• Yellow vein mosaic of bhindi (okra) is caused by the Bhendi Yellow Vein Mosaic Virus, a whitefly-transmitted begomovirus — a viral disease.

Checking each offered grouping against this classification: pairing Rust of wheat with Citrus canker wrongly bundles a fungal disease alongside a bacterial one; pairing Citrus canker with Yellow vein mosaic of bhindi wrongly bundles a viral disease alongside a bacterial one; and selecting Yellow vein mosaic of bhindi alone misidentifies a viral disease as bacterial.

Therefore, Citrus canker is the only disease among the three that is caused by bacteria.