Trunip mosaic and black rot of crucifers is due to

1. Viruses and bacteria respectively
2. Bacteria and viruses respectively
3. Bacteria and nematodes respectively]
4. Virus and nematodes respectively

The correct option is 1.
Turnip mosaic virus (TuMV) is a Potyvirus of the family Potyviridae that causes diseases in cruciferous plants, among others. The virus is usually spread by 40-50 species of aphids in a non-persistent manner. Infected plants, especially the natural hosts, show symptoms such as chlorotic local lesions, mosaic, mottling, puckering or rugosity. TuMV is a positive-sense single stranded RNA virus, consisting of a non-enveloped, helical capsid that is filamentous and flexuous, with an average length of 720 nm. The TuMV genome is linear and monopartite (single particle). The virus has a thermal inactivation point (TIP) of 62°C, and longevity in vitro (LIV) of 3–4 days.