First Report of Tomato Yellow Leaf Curl Virus in Réunion Island.

Abstract

In September 1997, stunting, reduced leaf size, leaf curling, and yellow margins were observed on tomato plants on a farm on the south coast of Réunion, a French island belonging to the Mascarenes archipelago. To our knowledge, these symptoms appeared to be characteristic of a tomato yellow leaf curl virus (TYLCV) infection. Diseased plants gave positive reactions with a triple antibody sandwich-enzyme-linked immunosorbent assay (TAS-ELISA), using ADGEN antibodies specific for begomoviruses (1). The serological results were confirmed by polymerase chain reaction (PCR) with a pair of degenerate primers-MP16, 5'-CCTCTAGATAATATTAC(C/T)(G/T)(G/A)(A/T)(T/G)G(G/A)CC-3' and MP82, 5'-CGGAATTC(T/C)TGNAC(C/T)TT(G/A)CANGGNCC(T/C)T C(G/A)CA-3'-designed by Malla Padidam (ILTAB, San Diego, CA) to amplify a region of the A component of begomoviruses, between the intergenic conserved nonanucleotide sequence (TAATATTAC) and the first 5' quarter of the capsid protein gene. A 500-bp PCR product was obtained from a symptomatic plant but not from a healthy looking one. After cloning the PCR product in a pGEM-T Easy vector (Promega, Madison, WI) and sequencing it with plasmid-specific primers (SP6, T7), the sequence was compared with the sequences of the NCBI data base, with the use of BLAST. Nineteen sequences among those producing the highest scoring segment pairs were compared with each other and with the 500-bp PCR product from Réunion by the Clustal method of MegAlign (DNASTAR, London). The Réunion sequence (AJ010790) was at least 94% similar to sequences of TYLCV isolates from the Dominican Republic (AF024715), Cuba (AJ223505), and Israel (X15656, X76319 for the mild clone). Based on these results, it appeared that the analyzed tomato plant was infected by a geminivirus isolate belonging to the Israeli species of TYLCV. A preliminary survey was carried out from December 1997 to April 1998 in both outdoor and protected tomato crops. Infected plants were detected by TAS-ELISA in 52 of the 123 locations visited. Severe economic losses were observed: 14 locations with 60 to 100% yield reduction and 11 locations with 40 to 60% yield reduction. All the infected samples were collected in the leeward coast, which is the driest region of the island. Although Bemisia tabaci (Gennadius) has been recorded since 1938 in Réunion (2), it has been observed on tomato crops only since 1997 and population levels were low compared with those of Trialeurodes vaporariorum Westwood. During the first six months of 1998, B. tabaci was found on Euphorbia heterophylla L., Lantana camara L., Solanum melongena L., S. nigrum L., and Phaseolus vulgaris L. These host plants often occur near infected tomato crops.