Tomato Yellow Leaf Curl Virus, a Whitefly-Borne Geminivirus of Tomatoes

Abstract

The first evidence of economic damage to vegetable crops caused by Bemisia tabaci Gennadius in Israel was recorded in 1931 (8), and since 1935 it has been a permanent pest, mainly in the Jordan Valley. The fluctuations in population size in different years were always directly correlated with the damage due to tomato yellow leaf curl virus (TYLCV). A TYLCV-like disease was first reported in Israel in 1939– 1940 and was associated with outbreaks of B. tabaci. The disease involved leaf curling, short internodes, leathery leaves, flower drop, and general dwarfing in comparison with healthy plants (8). Twenty years later, in 1959, when there was a heavy outbreak of B. tabaci in the Jordan and Bet She’an Valleys, the entire tomato crop was completely destroyed by a disease with the following syndrome: “Severe stunting of growth, the shoots are erect, and the leaflets are markedly smaller and misshapen. Those leaflets that appear soon after infection are cupped down and inwards, while subsequently developing leaves are strikingly chlorotic and show an upward curling of the leaflet margins. When young plants are attacked they lose vigor and hardly produce any marketable fruits” (25). The viral nature of the disease and its spread by B. tabaci were confirmed this time. The virus geminate shape was first observed in 1980 in electron microscope thin sections (82), but only in 1988 was TYLCV purified (32). From 1959 to date, TYLCV has spread to every region in Israel and become the major limiting factor in tomato production during both the summer and the winter.