In July 1998, shortened internodes, reduced leaf size, leaf curling, and bushy plants were observed in tomato crops in the coastal region near Casablanca, Morocco. The symptoms were similar to those described for tomato yellow leaf curl virus (TYLCV) disease. During September, the disease was present in more than 130 ha of outdoor and protected crops. Economic losses ranged between 20 and 100%. Similar symptoms were observed in tomato crops in the northeastern region of Morocco. During the same period, high populations of Bemisia tabaci (Gennadius) were observed on tomato, sweet pepper, and several weeds, including Sonchus oleraceus L., Chenopodium sp., Malva parviflora L., and Datura stramonium L. Attempts to control whiteflies with insecticides generally were unsuccessful. Using a pair of degenerate primers (3) that are expected to amplify a region of the A component of begomoviruses between the intergenic conserved nonanucleotide sequence and the first 5′ quarter of the capsid protein gene, an expected size product of 500 bp was obtained from six tomato leaf samples collected near Casablanca: four were obtained from symptomatic plants and two from apparently symptomless plants. A product of the same size was obtained from a sample of tomato infected with a TYLCV isolate from Reunion Island, France (2), but not from a sample from symptomless tomato plants from Reunion. The polymerase chain reaction (PCR) product obtained from one symptomatic sample from Morocco was cloned and sequenced (2). The resulting sequence (EMBL no. AJ133491) was at least 95.2% identical to sequences of TYLCV isolates from the Dominican Republic (EMBL no. AF024715), Cuba (EMBL no. AJ223505), Israel (EMBL no. X15656; EMBL no. X76319 for the mild clone), Spain (EMBL no. AF071228), and Reunion (EMBL no. AJ010790). Based on sequence comparisons, the tomato leaf sample was infected by a geminivirus isolate belonging to the Israeli species of TYLCV and was most closely related to the Dominican Republic isolate (98.4% nucleotide identity). In symptomless plants from which a 500-bp PCR product was obtained, infection may have been in an early stage. This is consistent with the fact that in the 2-ha field from which tomato samples were collected, only 4% of the plants exhibited TYLCV symptoms at the time of collection, whereas at least 70% of plants showed symptoms later, requiring the farmer to abandon the crop. The presence of the Eastern Mediterranean TYLCV species in a Western Mediterranean country is not a new observation; this virus has been described in Spain and Portugal (1). In Morocco, TYLCV symptoms were observed during the 1996 to 1997 growing season, following importation of grafted tomato plants from the Netherlands, by a farmer from the Casablanca region.
References: (1) J. Navas-Castillo et al. Plant Dis. 83:29, 1999. (2) M. Peterschmitt et al. Plant Dis. 83:303, 1999. (3) P. Umaharan et al. Phytopathology 88:1262, 1998.
