Observations on a Mixed Soil-Borne Wheat Mosaic Virus and Wheat Spindle Streak Mosaic Virus Infection in Durum Wheat (Triticum durum Desf.)

Both Wheat Spindle Streak Mosaic Virus (WSSMV) and Soil-borne Wheat Mosaic Virus (SBWMV) were found on durum wheat plants (Triticum durum Desf.) grown in a field near Rome (Italy). The simultaneous occurrence of these pathogens was demonstrated by host-symptomatology, pattern of disease occurrence in the field, mechanical transmission tests, as well as by the morphology of viral particles and of ultrastructural modifications. Negatively stained preparates of diseased leaves collected in early, spring showed WSSMV particles and cytoplasmic cylindrical inclusions. SBWMV particles were found only in samples collected later in the season. Ultrathin sections of infected leaves collected in early spring showed characteristic WSSMV modifications such as pinwheels and membranous bodies, whereas samples collected later in the season contained also SBWMV-like crystalline aggregates. WSSMV infection appeared to develop and decline earlier than SBWMV in the leaves of durum wheat plants infected by both, viruses. WSSMV had not been reported in Italy before.