Studies on a new disease of tomato in Spain called ‘torrao’ or ‘cribado’
Since spring 2001, a new disease called ‘cribado’ or ‘torrao’, has been observed on tomatoes grown under protected conditions in the region of Murcia, in Spain. Affected plants show necrotic lesions at the base of the leaflets, which later turn into shot holes (hence the Spanish name ‘cribado’). Longitudinal necrotic lesions also appear on the stems, necrotic line patterns or blotches followed by deformations appear on the fruits rendering them unmarketable. Affected plants present a general burnt-like appearance (hence the Spanish name ‘torrao’). In Spain, several methods were used to try to identify the causal agent (symptomatology, serology, molecular tests, electron microscopy and transmission trials) on a large number of symptomatic tomato samples during the last 6 years. On the basis of symptomatology, it was considered that the disease mainly occurs in Murcia and Islas Canarias (Tenerife, Gran Canaria) and to a lesser extent in Almeria (Andalucia), Alicante (Comunidad Valenciana) and Baleares (Mallorca). Similar symptoms were observed in the provinces of Vizcaya (Pais Vasco), Tarragona (Catalunya) and Valencia (Comunidad Valenciana) but were finally attributed to Parietaria mottle virus (Ilarvirus). Preliminary results of ELISA and PCR analysis showed that from a total of 369 samples, 67% tested positive for Pepino mosaic virus (Potexvirus – EPPO Alert List). However, in transmission assays, symptoms could only be reproduced in 2 plants grafted with infected plants (the rest of the inoculated plants showed typical symptoms of PepMV). Further molecular studies showed that 89% of the PepMV isolates detected in diseased tomato plants corresponded to the ‘Chilean 2’ isolate of PepMV.
In other studies done in the Netherlands (Verbeek et al., 2007), a new virus was isolated from tomato plants in Murcia showing similar symptoms and tentatively called Tomato torrado virus (ToTV). Phylogenetic analyses suggested that this new virus might belong to a new genus (close to Sequivirus, Sadwavirus and Cheravirus).
Following this report, further experiments were done in Spain and 94 samples, which had been collected in tomato glasshouses in Murcia from 2003 to 2006, were tested for the presence of this newly described virus (RT-PCR, molecular hybridization). 87 samples tested positive for ToTV. In 83 of these samples, ToTV was detected in association with PepMV (mainly ‘Chilean 2’ isolate). It is concluded that this new tomato disease is probably a syndrome involving ToTV and particular strains of PepMV, as well as other factors which remain to be determined.
Alfaro-Fernández A, Córdoba Sellés MC, Cebrían Micó MC, Font I, Juárez M, Medina V, Lacasa A, Sánchez Navarro, Pallás V, Jordá Gutiérrez C (2007) [Advances in the study of tomato ‘Torrao’ or ‘Cribado’ syndrome.]. Boletín de Sanidad Vegetal, Plagas 33(1), 99-109.
Alfaro-Fernández A, Córdoba Sellés MC, Cebrían Micó MC, Font I, Juárez M, Medina V, Lacasa A, Sánchez Navarro, Pallás V, Jordá Gutiérrez C (2006) [Tomato necrosis disease: ‘torrao’ or ‘cribado’]. Boletín de Sanidad Vegetal, Plagas 32(4), 545-562.
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