More than 1200 cultivars, breeding lines, and wild species of Lycopersicon were screened for resistance to the tomato leaf curl virus under field conditions. All accessions of Lycopersicon esculentum were found susceptible to tomato leaf curl virus. Three lines of Lycopersicon hirsutum and one of Lycopersicon peruvianum accessions showed apparent resistance to the tomato leaf curl virus owing to the failure of virus transmission by whiteflies. Morphological analysis by light and scanning electron microscopy revealed distributions of different types of trichomes on leaf surfaces. Lycopersicon hirsutum proved to be the least affected by the leaf curl virus because it did not support whitefly infestation to any extent. Lycopersicon hirsutum differed from other species by the presence of glandular trichomes designated type VIc. Whiteflies became entrapped in the exudate of type VIc trichome glands before they could transmit the virus. Thus, it may be possible to control tomato leaf curl virus transmission by breeding plants with certain types of trichomes, especially trichome type VIc. Key words: leaf curl virus, nonpreference, physical resistance, glandular exudate, trichomes, whitefly.

The ultrastructural modifications in nucleus of tomato infected with tomato leaf curl virus (TLCV) included hypertrophy of the nucleolus, segregation of nucleolar components into discrete granular and fibrillar regions, appearance of electron-dense particles associated ribbon-like structures, and presence of virus particles as either loosely compacted or hexagonally close-packed symmetrical arrays. The virus particles were isometric, about 18–20 nm in diameter. In the lumen of sieve elements, virus particles occasionally formed aggregates that were cylindrically arranged and occurred in pairs. Among the organelles other than the nucleus, virus particles were found in the plastids of sieve elements. In the chloroplasts of TLCV-infected cells, considerable disturbances in the internal organization were observed. In the most severe form of degeneration, the thylakoid system was fragmented and disorganized. In some chloroplasts starch grains were abnormally large. Excessive accumulation of osmiophilic bodies in degenerating chloroplasts was prominent. Key words: leaf curl virus, geminate particles, nucleolar hypertrophy, virus particles, osmiophilic body.