Geminivirdae Inclusions

Nuclear inclusions are considered to be a main characteristic of this group of plant viruses. These inclusions are aggregates of virus particles. Because geminivirus are DNA viruses the inclusions stain bluish to purplish in Azure A stain. (RNA viruses stain the color of the nucleolus. Compare the color of the nucleolus and the virus aggregates in the picture on the right.) The finding of blue-staining nuclear inclusions in the phloem tissues of an infected plant can help to diagnose a geminivirus infection.

Nuclear inclusions of tomato mottle begomovirus in phloem tissue.

(Inclusions of other geminiviruses tend to look like this in the light microscope - a large round blue inclusion in the nucleus. See bean golden mosaic inclusions below)

Nuclear inclusions of tomato yellow leaf curl in phloem tissue.

(Note that it is possible to diagnose these two viruses in tomato based on the morphology of their inclusions. Tomato yellow leaf curl begomovirus makes angular crystals or plates instead of the typical circular inculsion.)

Nuclear inclusions of bean golden mosaic begomovirus in bean. On the left are dark blue staining nuclei within the phloem tissue. On the right a closer magnification of bean golden nuclear inclusions.