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

Incidence, distribution and characteristics of major tomato leaf curl and mosaic virus diseases
ToMV is likely to occur in Uganda, where reports of its occurrence are actually based on
symptomatology (Defrancq, 1989; and Hansen, 1990) and therefore not very reliable.
2.1.1.1.2.2 Family Flexiviridae
This family has eight genera, which include Potexvirus, Carlavirus, Capillovirus,
Trichovirus, Foveavirus, Allexivirus, Vitivirus and Mandarivirus (Mayo and Brunt, 2005;
Adams et al., 2004). Its members have flexuous virions. Genera Carlavirus and
Potexvirus are known to infect tomato. The latter is a more important tomato virus genus
than the first, even though it is less important than other genera reported in this review.
2.1.1.1.2.2.1 Genus Potexvirus
This genus includes tomato-infecting virus species, Potato virus X (PVX). PVX is
considered to be of less economic importance to tomato production in tropical Africa
than other tomato viruses. Nono-Womdim et al. (1996), while reporting about other
tomato viruses, did not report PVX occurrence in Tanzania, and until this study it was not
known whether PVX infects tomato in Uganda.
2.1.1.1.2.3 Family Potyviridae
There are six member genera of this family, i.e. Bymovirus, Ipomovirus, Macluravirus,
Potyvirus, Rymovirus, Tritimovirus and (Mayo and Brunt, 2005; Pringle, 1999). Of
these, only the genus Potyvirus is known to have members that infect tomatoes.
2.1.1.1.2.3.1 Genus Potyvirus
This is the largest and economically most important group of plant viruses (Jones et al.,
1991). In the VIDE database index of plant viruses (2006), for every 10 virus species
listed at least one is a potyvirus. Potyviruses induce typical cylindrical, pinwheel-shaped
inclusions in cells of infected plants (Green and Kim, 1991). Some major viruses in this
family that infect tomato include Potato virus Y (PVY), and Pepper veinal mottle virus
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