SURVEY ON VIRUS DISEASES AFFECTING RANUNCULUS HYBRIDS IN LIGURIA

In 2005-2006, two hundred samples of Ranunculus hybrids collected in Sanremo area (Liguria region) were examined to verify the presence of viruses associated to severe symptoms on leaves (chlorosis, mosaic, “parsely-like” appearance, vein-yellowing, necrotic spots and rings), flowers (colour breaking, malformations) and/or to the prematurely death of plants. By applying virological tests: mechanical inoculations on herbaceous plants, electron microscopy (“leaf-dip”), DAS and PAS-ELISA, IME (“decoration”), and RT-PCR, virus particles of different lengths (from 700 to 800 nm) and sizes (from 30 to 90-100 nm) singly or in mixed infections were detected. Cucumber mosaic virus (CMV) in a few cases alone, much more in combination with Tomato spotted wilt virus (TSWV) infected plants showing leaf mosaic, necrosis, stunting and severe symptoms on flowers. Both TSWV and Impatiens necrotic spots virus (INSV), in some cases with also Potato virus Y-Ranunculus strain (PVY-R), were detected in the foliage characterized by mosaic, necrosis and “parsely-like” symptoms. Turnip mosaic virus (TuMV) and other unidentified potyvirus-like viruses were found. CMV and all the Potyviruses detected, were much present during Autumn 2006 season as a consequence of the abundance of aphid infestations. Data obtained clearly show not only the high diffusion of different species of viruses in Ranunculus crops in Sanremo area, but also that the correlation between symptom expression and virus presence is very difficult to be explained. Considering the increasing of economic damages to cut flower production recently observed, control measures to prevent virus spreading are required.