Survey of virus diseases of Polygala myrtifolia in Liguria

In 2005-2006, two hundred samples of Ranunculus hybrids collected in the Sanremo area (Liguria, northern Italy) were examined for the presence of viruses associated with severe symptoms on the leaves (chlorosis, mosaic, "parsely-like" appearance, vein-yellowing, necrotic spots and rings), flowers (colour breaking, malformations) and/or with premature death of the plants. Through mechanical inoculations to herbaceous plants, electron microscopy ("leaf-dip"), DAS and PAS-ELISA, IEM ("decoration"), and RT-PCR, virus particles of different length (from 700 to 800 nm) and diameter (from 30 to 90-100 nm) were detected singly or in mixed infections. Cucumber mosaic virus (CMV), alone in a few cases, more frequently in mixture with Tomato spotted wilt virus (TSWV) occurred in plants showing leaf mosaic, necrosis, stunting and severe symptoms on the flowers. Both TSWV and Impatiens necrotic spot virus (INSV), in some cases in assoaciation with the Ranunculus strain of Potato virus Y (PVY-R), were detected in plants characterized by mosaic, necrosis and "parsely-like" apperance of the leaves. Turnip mosaic virus (TuMV) and other unidentified potyvirus-like viruses were also encountered. CMV and all potyviruses prevailed in Autumn 2006 possibly as a consequence of the heavy aphid infestations. Our resaults clearly show not only that different virus species are widely present in Ranunculus crops in the Sanremo area, but also that a correlation between symptom expression and infecting virus is very difficult to establish. Considering the increased economic damages to cut flower production recently observed, control measures to prevent virus spreading are required.