are extremely grateful for the financial support provided by Instituto Nacional de Investigaciones Agrarias by
means of the Project N° SC93-183-C3-1.
Literature cited:
Abad, P., 1996. Tomato spotted wilt virus: dinamica de la enfermedad y caracterizacian de aislados. Tesis
doctoral. Universidad Politecnica de Valencia. 186 pp.
Diez, M.J., Rosello, S., Jorda, C., Lacasa, A., Costa, J. and Nuez, F., 1995. Agronomic behaviour of resistant
tomato cvs. and lines to TSWV and influence of inoculation methods. Acta Hortic. 402:527-532.
lizuka, N., Boiteux, L.S., Giordano, L. De B., Nagata, T. and Dusi, A.N. 1993. Sources of resistance to tomato
spotted wilt virus (TSWV) in wild Lycopersicon species. TGC Report, 43: 20-22.
Krishna Kumar, N. K. and Ullman, D. E. 1993. Evaluation of Lycopersicon germplasm for tomato spotted wilt
tospovirus resistance by mechanical and thrips transmission. Plant Dis., 77: 938-941.
Paterson, R.G., Scott, S.J. and Gergerich, R.C., 1989. Resistance in two Lycopersicon species to an Arkansas
isolate of tomato spotted wilt virus. Euphytica 43: 173-178.
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Studies on seed-borne pathogens of tomato (Lycopersicon esculentum Mill) in Sudan.
Salman, K.A.; Mohamed, Y.F. and Dafalla, G.A.
Plant Pathology Centre, Gezira University, Wad Medani, P.O. Box 20, SUDAN
Tomato is one of the most important vegetable crops and ranks second after onion in Sudan. Almost all
tomato seeds are imported and distributed to farmers through seed retailers. Seed importation is not organized
business, so all kinds of tomato varieties are found in the market. Consequently, problems of climatic unsuitability
and those connected with seed-borne pathogens may lead to substantial yield losses.
Studies conducted during the period extending from 1992 to 1995 using different seed samples collected
from tomato grown in different locations in Gezira scheme (Central Sudan) were examined for the presence of
bacterial, viral and fungal seed-borne pathogens using various techniques.
Through the use of differential media, five different bacteria were isolated and identified following LelIiott
and Stead (1987) procedures for plant pathogenic bacteria identification. Depending upon their reactions towards
the applied morphological, biochemical, biological and some confirmatory tests, they were identified as follows:
Erwinia herbicola, Pseudomonas viridiflava, Xanthomonas campestris pv. vesicatoria, Clavibacter michiganesis
subsp. michiganesis and Pseudomonas syringae pv. tomato. The pathogenicity of the last three listed bacteria is
confirmed and they cause considerable crop losses during in rainy season crop. To our knowledge this is the first
report about the existence of P. syringae pv. tomato in Sudan.
Using two of the incubation methods (Blotter and Agar-plate methods), identification of the fungi was
achieved by using both stem-binocular and compound microscopes, and the following fungi were recorded:
Alternaria tenuis, Aspergillus spp, Chaetomium spp, Cladosporium spp, Fusarium spp, Phoma sp, Rhizopus spp,
and Penicellium spp. With the exception of Fusarium and A. tenuis, all the isolated genera are seed rotters, and
cause germination failure as reported by Sati et al .(1989) and Silva et at. (1991).
Using growing-on test and DAS-ELISA, tomato or tobacco mosaic virus (TMV) was detected in the
majority of the tested seed samples. The commercial varieties, Strain B from
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