Current Status and Newly Discovered Natural Hosts of Tomato infectious chlorosis virus and Tomato chlorosis virus in Spain.

Tomato chlorosis virus (ToCV) and Tomato infectious chlorosis virus (TICV) are emergent whitefly-transmitted criniviruses. ToCV and TICV were detected in Spain in 2000 (2) and 2001 (1), respectively. Both viruses infect tomato (Lycopersicon esculentum Mill) crops and cause symptoms of foliar chlorosis. ToCV is prevalent along the southern and eastern regions of Spain (provinces of Sevilla, Málaga, Almería, Murcia, Alicante, and Castellón), Balearic (Mallorca), and the Canary Islands (Tenerife and Gran Canaria). However, TICV only has been detected in the provinces of Murcia, Alicante, and Castellón in Spain. During the summer and autumn of 2002, abnormal interveinal reddening, yellowing symptoms, or both, were observed in plants of Chenopodium album L., C. murale L., and Solanum nigrum L. growing in or around tomato fields in Murcia and Almería provinces. To study the alternative hosts that may serve as virus reservoirs in areas where these viruses are prevalent, 62 samples of 42 common weed species were analyzed by reverse transcription-polymerase chain reaction using specific primers for ToCV and TICV (1). The 439-bp ToCV-specific DNA fragment was amplified in two S. nigrum samples from Alicante and Murcia provinces, and the 501-bp TICV-specific DNA fragment was amplified in one C. murale sample from Murcia, as well as in three C. album samples from Murcia and Alicante provinces. The DNA fragment amplified from the ToCV isolate was sequenced and showed 99 to 98% identity with the ToCV isolates (GenBank Accession Nos. AY048854 and AF234029) from Italy and Portugal, respectively. The DNA fragment amplified from TICV isolates were sequenced and showed 98% identity with the TICV isolate from Spain (GenBank Accession No. AF479662), confirming the diagnosis. Although the number of samples is not sufficient to conclude that we know, in a precise way, the role of weed reservoirs in TICV and ToCV epidemics in Spain, this study might contribute to a better understanding of the epidemiology of these viruses. To our knowledge this is the first report of these weeds as natural hosts of ToCV and TICV in Spain. References: (1) M. I. Font et al. Plant Dis. 86:696, 2002. (2) J. Navas-Castillo et al. Plant Dis. 84:835, 2000.