First report of Tomato brown rugose fruit virus infecting sweet pepper in Italy

Abstract

In January 2020, about 85% of a red sweet pepper (Capsicum annuum) crop in a greenhouse located in Ragusa province (Sicily, Italy) showed virus-like symptoms. Symptoms consisted of a slight mosaic and discoloration of young leaves, vein clearing on young leaves, browning of the stem with strong necrosis located in the intersection of the secondary branches, partial necrosis of the vegetative apex and marbling, mosaic and distortion of the fruits (Fig. 1). It is important to note that in 2019 the same greenhouse was cultivated with tomato, which had been removed due to extensive infection caused by Tomato brown rugose fruit virus (Panno et al., 2019a). Thirty plants (15 diseased and 15 asymptomatic) were collected for subsequent analysis. In order to ascertain the causal agent of the disease, the samples were tested for the presence of Cucumber mosaic virus (CMV) and Tomato spotted wilt virus (TSWV) by RT-PCR (Panno et al., 2012), and for Tomato brown rugose fruit virus (ToBRFV) by immunocapture (IC) real time RT-PCR (Panno et al., 2019b). The results were negative for CMV and TSWV in all 30 samples while 18 samples (15 diseased and three asymptomatic) gave a positive signal in IC-real time RT-PCR. To confirm the presence of ToBRFV, RT-PCR with specific primers ToBRFV-F and ToBRFV-R (Alkowni et al., 2019) was done. Amplicons of the expected size, 560 bp, were obtained for the 15 diseased plants, while only one asymptomatic plant gave positive results. Four amplicons (three diseased and one asymptomatic plant) were purified using