Incidence, Distribution and Characteristics of Major Tomato Leaf ...

Incidence, distribution and characteristics of major tomato leaf curl and mosaic virus diseases
Cohen and Antignus (1994), Mazyad et al. (1994), as well as Greer and Dole (2003) used
cultural practices, such as yellow traps and mulches, intercropping tomato with other crop
species, and physical barriers to reduce whitefly movement. Kasrawi et al. (1988),
Lapidot and Friedmann (2002), Rubio et al. (2003), Yang et al. (2004), de Castro et al.
(2005), and Fuentes et al. (2006) aimed at controlling TYLCV by breeding or
engineering for resistance, while Berlinger and Dahan (1985), and Kisha (1984)
researched into host plant resistance to the whitefly vector. All these approaches depend
on accurate virus identification to avoid targeting a wrong pathogen (Hamilton et al.,
1981; Bock, 1982).
2.1.1.1.1.2 Family Closteroviridae
This family includes two genera, Closterovirus and Crinivirus. A virus, which causes
infectious tomato chlorosis, was attributed to the genus Closterovirus (Wisler, 1998).
However, the International Committee for the Taxonomy of Viruses (ICTV) later
classified it as a member of genus Crinivirus (Fauquet and Mayo, 1999). As such, genus
Closterovirus has no yet known tomato virus.
2.1.1.1.1.2.1 Genus Crinivirus
Whiteflies transmit criniviruses. These viruses are RNA flexuous filamentous rods, 600 –
2000 nm long. Closteroviruses cause general leaf yellowing, vein chlorosis and phloem
necrosis in susceptible hosts (Duffus, 1995). They are reported to be associated with
intracellular inclusions and vesicles. Their coat protein has a molecular weight ranging
from 23 kD – 27 kD, whereas their nucleic acid (RNA) has a molecular weight of 2,000
kD - 4,500 kD (Duffus, 1995). A member of this genus that infects tomato is the Tomato
infectious chlorosis virus (TICV).
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