Rice tungro disease is caused by:

Correct option is D

• Rice tungro bacilliform virus (RTBV) – a bacilliform (rod-shaped) DNA virus

• Rice tungro spherical virus (RTSV) – a spherical RNA virus

• Vector: Green leafhopper (Nephotettix virescens)

• Symptoms: Yellowing, stunting, reduced tillering, and poor grain filling

• Control Measures: Use of resistant varieties, vector control, and field sanitation

• A mixture of spherical and flexuous viruses: Flexuous viruses (like Potyviruses) are not associated with tungro.

• A bacilliform virus alone: RTBV alone cannot cause the full disease symptoms; it needs RTSV for effective transmission and severity.

• A mixture of bacilliform and flexuous viruses: No flexuous virus is involved in tungro disease. Only spherical and bacilliform viruses are responsible.