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

Incidence, distribution and characteristics of major tomato leaf curl and mosaic virus diseases
3.3.1 Incidence of Virus-like Symptoms in the Field
Symptoms observed in the field were mosaic, mottling, and curl. Others were not easy to
describe as they showed an overlap of different symptoms, and so were referred to as
“miscellaneous”. Leaf curl virus disease-like symptoms were most prevalent with a mean
incidence of 42%, especially in Iganga (66%) and Kasese (66%) districts, followed by
leaf mosaic with 26% and then mottling symptoms with 13%. Mosaic was most common
in Mpigi (45%), whereas mottling occurred most frequently in Kasese with 36% (Table
3.6). In Kabale 87% of the symptoms had miscellaneous symptoms characterized by
general leaf yellowing, with only 6% leaf curl and 7% mosaic symptom-bearing samples,
and because of this high percentage of miscellaneous one in Kabale, we get the 19%.
Table 3.6 Percentage number of samples showing characteristic symptoms of tomato
viruses as observed per district surveyed in 1997-1998
Districts/
Symptoms
Rakai Mpigi Iganga Mbale Mbarara Kasese Mukono Kabale Mean
Mosaic 31 45 4 43 36 0 39 7 26
Mottling 10 16 0 26 19 36 0 0 13
Curl 49 37 66 20 43 66 52 6 42
Miscellaneous 10 2 30 11 2 6 7 87 19
3.3.2 Confirmation of Symptoms and Identification of Viruses
3.3.2.1 Confirmation of Virus Symptoms Through DAS-ELISA
In order to confirm the fact that symptoms observed on tomato were indeed due to
viruses, serological tests were conducted. DAS-ELISA results indicated that there was no
symptom specific to particular groups of viruses. Samples that tested positive for ToMV,
AMV, PVMV, and TSWV either had mosaic, mottling, crinkling or leaf curl symptoms.
Viruses occurred singularly or in mixtures whereby two or more viruses infected one
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