Incidence and Etiology of Branch Wilt due to Nattrassia mangiferae (Nattrass) on Selected Tree Flora in Khartoum State

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El Atta, H.A.
Nori, W.M.
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Faculty of Agriculture, University of Khartoum, Shambat, Sudan
A survey of Ficus benjamina L. and F. nitida Thunb for the branch wilt disease revealed high levels of infection in both species at Africa International University (AIU) and Faculty of Agriculture in Shambat. At AIU, the frequency of infestation was 100% in F. benjamina and 95% in F. nitida, while at Shambat it was 79 and 33% in F. benjamina and F. nitida, respectively. Isolation of microorganisms from plant material and soil samples beneath infected trees on PDA revealed that Nattrassia mangiferae Nattrass was the dominant species. Four isolates of N. mangiferae were obtained; isolates 1 and 2 with spherical spores and isolates 3 and 4 with cylindrical spores. The symptoms of the branch wilt included leaf chlorosis, necrosis, defoliation, peeling off of the bark of branches and mortality of the host plant. The most characteristic feature of the disease is the presence of heavy masses of a black layer of spores under the bark. Pathogenicity tests proved that the causal organism was N. mangiferae as it was the only pathogenic fungus recovered from inoculated seedlings and always associated with the symptoms recorded on naturally infected plants. Stem inoculations were more successful as compared to root inoculations. F. benjamina developed symptoms faster than F. nitida, following artificial inoculation. The host range experiments indicated that a number of taxonomically unrelated tree species was variably susceptible to infection by N. mangiferae, namely Khaya senegalensis (Desr.) A. Juss., Ficus benegalensis L., Eucalyptus camaldulensis Dehn., Azadirachta indica A. and Acacia senegal L. The role played by some cultural practices in the epidemiology of this disease is discussed.
Page(s): 7 (1), 116-129,9Ref.