Molecular Characterization of Tomato Leaf Curl
Disease-Causing Viruses in Uganda
Ssekyewa Charles, Van Damme P. & Steele K. A.
In this study, Tomato Leaf Curl Disease symptom-bearing samples were collected from dry savannah
(Eastern and Northern) and wet equatorial/tall grass savannah (Central and Western) agro-climatc
zones of Uganda. Their total DNA was extracted using a modified Dellaporta protocol. Virus DNA
was amplified with five different primer pairs for Tomato yellow leaf curl virus (TYLCV), Tomato
yellow leaf curl Sardinia virus (TYLCSV-Sic) and Tomato leaf curl Uganda virus (TLCUV) as well as
their combinatons. The results indicated that there is wide variaton in the tomato leaf curl viruses
in the Country. The viruses were grouped into 24 categories and three (3) distnct virus genomes,
namely, Tomato leaf curl Uganda virus-Sorot, Tomato leaf curl Uganda virus- Iganga (Pallisa) and
Tomato leaf curl Arusha virus-Mubende, were characterized. Partal results indicated occurrence of
viruses related to TYLCV and TYLCSV-Sic in wet agro-climatc zones. Genomic variaton was detected
within isolates and recombinaton was suspected.
Key words: Tomato; Begomoviruses; Genome; Co-Evoluton; Recombinaton
Introduction
Tomato (Solanum lycoperscicum) is a fruiting vegetable. It originated in Latin America and has become
one of the most widely grown vegetables, with ability to produce in diverse environmental conditions
(Rice et al., 1987). The tomato fruit is fairly rich in vitamins A and C; is of high cash value; and has
much potential for value-adding processing. In Uganda, about 5-30% of the farming households grow
tomato, not only as a source of vitamins and food security, but also as a source of income (Ssekyewa,
2006). Tomato grows best in fertile, well-drained soils, with pH6 and ambient temperatures of about
25
0
C (Villareal, 1979; Rice et al., 1987), which are common in Uganda (Mukiibi, 2001). Thus, National
Agricultural Research Organization (NARO, 1999) prioritizes it among the vegetables to be promoted
in the country.
With proper management practices, a smallholder commercial farmer is expected to reap at least 100t/ha
(AVRDC, 1994). In Uganda, however, average yield is 10t/ha (Ssekyewa, 2006). This is due to a number
of factors, including the use of unimproved varieties, occurrence of pests and diseases and ignorance
about sustainable agronomical practices (Akemo et al., 2001). Caribe, Magrobe, Pakmor and Tropic
tomato varieties are reported to be acceptable to farmers and consumers in Uganda while VF 6203 and
Peto-C-8100 159, which have resistance to Verticilium and Fusarium, are recommended for processing
(Mwaule, 1995). Mwaule (1995) and Akemo et al. (2001) also confrmed the World Vegetable Centre’s
MT 40, 41, 55, 56 and 57 tomato lines to be resistant to bacterial wilt (Ralstonia solanacearum). It is also
Journal of Science and Sustainable Development
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ISSN: 200-1; Vol 2 (1): 11—22
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