Changes occurring in Gomphrena globosa leaves in advance of the appearance of tomato bushy stunt virus necrotic local lesions

Abstract

Comphrena globosa leaves react to tomato bushy stunt virus giving, 30 h after inoculation, yellowish fluorescent spots which develop into necrotic lesions 8 h later. Thin sectioning of these spots revealed alterations of chloroplasts, mitochondria, cell walls, plasma membrane, and small groups of virus particles. Some cells showed severe degeneration presaging collapse and necrosis. The appearance of the fluorescent spots coincided with the accumulation of a flavonoid whose synthesis did not involve an increase of phenylalanine ammonia lyase activity. Significant increases in electrolyte leakage occurred starting from 5 h after inoculation. The release of electrolyte progressively increased with time and was very large from 25 h. The early electrolyte leakage, probably due to a change in permeability of the plasma membrane alone, cannot be the cause of the necrosis, and may be a consequence of an interaction between viral particles and plasma membrane.