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

Incidence, distribution and characteristics of major tomato leaf curl and mosaic virus diseases
Therefore, both degenerate and specific primers could be used to identify and
characterise TYLCV occurring in Uganda.
A more recent and improved PCR now exists. It employs more than one primer pair,
mostly specific ones, to target specific parts of the replication gene and intergenic region.
This method is called multiplex PCR (Potter et al., 2003; Gorsane et al., 2005), and it is
reported to be faster and even cheaper than the PCR technique described above.
Distribution of Tomato Yellow Leaf Curl Viruses
TYLCV is quite general in the tropics. In Africa, it has been reported from South Africa,
Senegal, Tanzania, Malawi, Zambia, Zimbabwe, Nigeria, Ivory Coast, Egypt and Sudan
(Yassin et al., 1982; AVRDC, 1987; Czosneck et al.1990; Nakhla et al., 1993; AVRDC,
1993; Nono-Womdim et al, 1994; Chiang et al., 1996). It is also widespread in the rest
of the Old World and in the New World, e.g. in South East Asia and East Asia, the
Americas and the Mediterranean (Green and Kallo, 1994; Chiang et al., 1996; Polston
and Anderson, 1997; Czosnek and Laterrot, 1997). Therefore, it is likely that the virus
also occurs in Uganda, since it affects tomato in neighbouring countries, which have
similar climatic conditions. This suggests the need to investigate the presence and status
of TYLCV in Uganda.
Transmission of Tomato Yellow Leaf Curl Viruses
TYLCV is transmitted by a whitefly (Bemisia tabaci Gennadius) of the Family
Aleyrodidae (Cohen and Nitzany, 1966; Nakhla et al., 1978; Gerling and Mayer, 1995).
Bemisia tabaci occurs in biotypes A and B. Biotype B is more common than A and is
regarded by some as a separate species designated B. argentifolii (Bellows et al., 1994).
Others continue to regard it as a biotype of B. tabaci, even though there are many more
biotypes, which include biotype Q (Demichelis et al., 2000).
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