Effect of Contaminating Fungi and Their Control in Seeds of Different Quality and in Accelerated (Rapid) Aging Tests of Soybeans

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Mcgee, D.C.
Olembo, S.A.H.
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The effects of Aspergillus flavus, A. niger,Penicillium oxalicum and Rhizopus sp.the commonly occurring facultative contaminants in seed germination test were studied on seeds of different quality and in the "accelerated aging tests “of soybeans. Isolates were obtained using the Andepsen air sampler from air in the germination laboratory at Iowa State University. Seeds of the cultivar Amsoy 71 were either o( good quality. Mechanically damaged or aged. Appropriate samples were inoculated by separately dipping 250 g of seed into spore suspensions of each of the following fungi: A. flavus, A niger. P. oxalicum and Rhzopus sp. Spore suspensions were diluted to 23 x 106 spores/ml. When treatments required aging the seeds were aged for various periods and treated especially with a fungicide (Captan) and an antibiotic (Nystatin) or left untreated. Alternatively seeds were inoculated and then treated .with the fungicide or antibiotic prior to aging. Aging was done in open petri dishes held in a chamber at 100% RH and 40-41°C. Malformed seedlings in inoculated tests were more pronounced in poorer quality seeds than in good quality seeds and were reduced by Captan seed treatments. However, results indicated no beneficial effects when seeds that had been inoculated and aged were treated with Captan at 5.5 ml/kg or Nystatin at 0.3 g/l before the germination tests. Captan at these rates and Nystatin at 0.3 gm/l significantly increased the emergence of these tests only when applied before aging.
East African Agricultural And Forestry Journal, 60 (No. 3), pp. 157-165