The following points highlight the six main symptoms of viral diseases. The symptoms are: 1. Mosaic Spotting 2. Ring Spotting 3. Chlorosis 4. Distortion 5. Necrosis 6. Breaking of Blossoms. Symptom # 1. Mosaic Spotting: In this case usually the leaves, sometimes the blossoms and other parts of the host plants show spots or patches of light green, yellow or [...]
The following points highlight the two main theories on living hypothesis of viruses. The theories are: 1. Organism Theory 2. Molecular Theory. Theory # 1. Organism Theory: The supporters of the living hypothesis argue that growth and reproduction are chief distinctive characteristics of living things (organisms). Viruses possess both. They grow, reproduce and undergo mutations and become adapted to the [...]
In this article we will discuss about viroids which are smallest known agents of infectious diseases and are not related to viruses. Subject-Matter of Viroids: Diener (1971), during his studies on Potato spindle Tuber disease assumed to be caused by a virus, discovered that the causal organism was made up of naked free RNA devoid of protein coat. Except for [...]