Stress-related expression of virus symptoms in fig (Ficus carica L.)

Abstract

Some reports indicate that virus infection can bring about plant stress. However, there is no report pointing to an environmentally stressed host plant that triggered the conversion of a latent, harbored RNA virus into an active, pathogenic agent. The observation documented here on fig trees (Ficus carica) is the first account of a host plant species in which a latent virus is converted into a rapidly propagating virus, causing severe pathogenic symptoms. All the old clones of figs worldwide harbor the causative agent of the mosaic disease. The conversion of this agent from a latent to a pathogenic state was linked to stress inflicted on the trees by pruning and bending the twigs for trellising, followed by hot weather. The stress inflicted on the trees resulted in the appearance of severe mosaic symptoms. Other fig trees of the same age and grown from cuttings from the same source but not trained and left undisturbed hardly showed fig mosaic symptoms. All the trees were pruned similarly during winter dor...