HIGH GENETIC STABILITY IN NATURAL-POPULATIONS OF THE PLANT RNA VIRUS TOBACCO MILD GREEN MOSAIC-VIRUS

Quantitative studies on the genetic variation of plant viruses are very scare, in spite of their theoretical and applied importance. We report here on the genetic variability of field isolates of the plant RNA virus tobacco mild green mosaic virus (TMGMV) naturally infecting the wild plant Nicotiana glauca Grah. The populations studies were composed of a high number of haplotypes. Two main features are found regarding TMGMV variation: First, there is no correlation between genetic proximity of isolates and geographic proximity of the sites from which they were obtained; and second, the estimated divergence among haplotypes is low, and values are maintained regardless of the scale of the distance between the sites from which the isolates come. No comparable studies have been done with a plant RNA virus, and these two features seem to be unique for this system as compared with other RNA viruses.