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Incidence, distribution and characteristics of major tomato leaf curl and mosaic virus diseases Number of infected plants Disease incidence (%) = …………………………………x 100 (6), Number of plants in the field was recorded and estimated as percentage infection, whereby 1-20% =low incidence; 21- 49% = moderate incidence; and 50 - 100% = high incidence (Nono-Womdim et al., 1996). In the laboratory, samples were first grouped according to symptoms, which included mosaic, mottling and leaf curl (Figures 3.3, 3.4, and 3.5). Those samples with no definite symptoms were grouped under ‘miscellaneous’ (Figure 3.6), as compared to healthy plant leaves (Figure 3.2). Because tomato yellow leaf curl is reported to be caused by more than one virus species (Czosnek and Laterrot, 1997) and the causal agent was earlier on demonstrated to be a geminivirus (Cohen and Harpaz, 1964) with no known efficient antisera, each sample that expressed tomato leaf curl symptoms was also squash-blotted onto High Bond Nylon membrane as described by Czosnek et al. (1988); Czosnek et al. (1990) and Green and Kalloo (1994). Squash-blotted Nylon membranes were later taken to the Laboratory of Professor. D. Maxwell, University of Wisconsin-Madison, USA, for DNA hybridisation. Some of these samples were treated and dried like any other in preparation for later Polymerase Chain Reaction (Czosnek et al., 1988) studies. Some other collected samples were chopped into small pieces, prior to sample analysis. After chopping each sample, the knife was dipped into ethanol and heated over a spirit burner flame to avoid contaminating subsequent samples. Leaf pieces were then put on a filter paper and sealed in petridishes over anhydrous calcium chloride to dry at 4ºC (Green, 1991), and were kept in those conditions for 5-9 months. Later on, each sample was put in a labelled self-sealing polythene bag over anhydrous calcium chloride for easy transportation to the World Vegetable Centre (AVRDC) Associated Laboratory at Horti- Tengeru, Arusha, Tanzania, specifically to conduct DAS-ELISA tests that could not be done in Uganda at the time. 50
Incidence, distribution and characteristics of major tomato leaf curl and mosaic virus diseases Table 3.1: Agro-climatic zones of Uganda and major characteristics of production systems (NARO, 1999). Surveyed districts are underlined. Agroecological zone Long Rain Unimodal Production system/Districts Major traditional cash and food crops Production constraints and challenges (NARO, 1999) Northern: Gulu and Kitgum Cotton, tobacco, sesame, sorghum, cassava, groundnuts Poor road and storage infrastructure and finger millet. and distance to markets Transitional Eastern: Katakwi, Kumi, Soroti, Cotton, finger millet, groundnuts, cassava, rice, sweet Declining soil fertility and Tororo, and Pallisa potato, and cowpeas unreliable rainfall Mid-Northern: Apac and Lira Cotton, sesame, sorghum, cassava, pigeon peas, beans, Declining soil fertility and sunflower unreliable rainfall Lake Albert Crescent: Masindi, Cotton, bananas, finger millet, cassava, maize beans, Declining soil productivity Hoima, Kibaale. South-Eastern: Iganga, Bugiri, Busia, Kamuli, Jjinja. groundnuts, citrus Bimodal Lake Victoria Crescent: Mukono, Robusta coffee, banana, maize, tea, vanilla, beans, Pests and Diseases rainfall Mpigi, Masaka, Nakasongola, Luwero, Kiboga, Mubende, Rakai horticultural crops Montane Eastern Highlands: Mbale and Maize, wheat, arabica coffee, banana, finger millet, Population pressure and declining Kapchorwa beans soil productivity Southernhighlands: Kabale, Irish potatoes, sorghum, finger millet, peas and onions Population pressure and declining Kisoro and Rukungiri soil productivity Western highlands: Kasese, Banana, cassava, sweet potato, finger millet, beans, Inadequate infrastructure and access Bundibudyo, Kabarole and Bushenyi maize, arabica coffee, cotton and passion fruits to market Dryland Karamoja: Kotido and Moroto Sorghum, cowpeas, pearl millet and finger millet Overstocking and environmental degradation Southern: Mbarara, Sembabule, Beans, finger millet, and banana Overstocking and environmental Ntungamo, and Rakai degradation 51
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Incidence, Distribution and Charact
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Charles SSEKYEWA Incidence, Distrib
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CONTENTS 1 CHAPTER 1...............
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ACKNOWLEDGEMENT The following perso
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vii 7 mosaic virus (CMV), Alfalfa m
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ix 9 Consequently, our findings con
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SAMENVATTING Tomaat is een economis
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xiii 13 Beide genhomologie percenta
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xv 15 dit onderzoek geven ook aan d
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LIST OF TABLES xvii 17 Table Page 1
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ACRONYMS AND ABBREVIATIONS xix 19 A
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1200 1200 (A) IG1 (ToLCV-UG) PAL1v
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A A C D Incidence, distribution and
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Opaque and not smeared Translucent
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8 ANNEXES Incidence, distribution a
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Table A.1.1 continued Incidence, di
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