Severe outbreak of tomato yellow leaf curl Sardinia virus on pepper in southern Italy

During summer and autumn 2008 a severe outbreak of pepper leaf curl disease (PLCD) was observed in pepper crops under plastic tunnels in the ionic coast of Basilicata region. Its incidence reached, in some cases, values close to 50%. The beginning of infections was recorded along the perimeter of the tunnels, where it reached a percentage of almost 100%. The infection then progressively spread towards the central areas of the greenhouses. Large populations of whiteflies, identificated as Bemisia tabaci, were observed on the infected crops. Detection assays for TYLCSV and TYLCV were performed in order to ascertain the etiologic agent: 190 symptomatic samples were collected from different fields and assayed in DAS-ELISA using a broad-spectrum reagent combination (distributed by Bioreba AG) detecting TYLCV, TYLCSV and other Begamoviruses: of these, 176 samples resulted positive. In order to discriminate between TYLCSV, TYLCV or any other Begamovirus, 15 positive samples were analyzed by PCR using a couple of synthetic oligonucleotides allowing the amplification of the whole coat protein (CP) gene. RFLP analysis performed on the PCR product, 1008 bp long, showed the presence of only TYLCSV in all assayed samples. The molecular characterization performed by phylogenetic analysis of the sequenced coat protein gene revealed that the isolate shares a similarity of about 97% with the corresponding sequence of a tomato TYLCSV isolate from Sicily (Z28390) and is almost identical with the pepper isolate CAB-It recovered in the same area in 2007 (TYLCSV was first recorded on pepper in Italy in 2007 in Policoro-MT, Fanigliulo et al., 2008. Comm. Appl. Biol. Sci, Ghent University, 73/2, 2008), indicating that there is a very low variability in TYLCSV population in the surveyed area. The further diffusion of PLCD and its hazard has to be connected with the presence of wide tomato cultivations, of weed hosts alternative to pepper (Solanum nigrum, Datura stramonium, Sonchus asper, Cardaria draba and Abutilon theophrasti) and with the strong presence of the vector B. tabaci of the B biotype, more efficient than Q biotype in the virus transmission, and able to feed and reproduce on peppers as well as on tomatoes.