Cytopathological changes in Schefflera actinophylla Harms. naturally infected with impatiens necrotic spot virus (INSV)

Abstract

Plants of Schefflera actinophylla Harms. with stunted growth, chlorotic and necrotic spots and patterns, leaf epinasty and distortion are infected with impatiens necrotic spot virus classified as a member of genus Tospovirus. Studies with electron microscope revealed that in cells of S. actinophylla leaves there were no virus particle inclusions typical for tospovirus infection, but only single particles were present. The isolate of INSV was defective and the amount of INSV particles was strongly reduced in Schefflera plants. Some inclusions (I type) were composed of short branched cisterns of endoplasmic reticulum and a dark substance forming characteristic bands. The II type represented inclusions that were usually ballshaped and composed of a dark substance resembling that of the I type, but not accompanied by endoplasmic reticulum cisterns. The III type of inclusions was composed of dark, osmophilic masses. The inclusions present in the cells differ from those typical for tospovirus infection.