Effects of Temperature on the Simultaneous Production of Zearalenone and Deoxynivalenol by Fusarium Graminearum on Maize

Fusarium graminearum (Schwabe), a fungus commonly encountered on maize ( Zea mays L) in Zambia, was analyzed for toxin production under temperature conditions prevalent during periods of high infestations. Ground maize samples were adjusted to a moisture content of 40% and inoculated with an isolate of F. graminearum. The samples were incubated at 26\ub0C or 16\ub0C for 10 weeks. Samples were analyzed for the toxins, zearalenone, deoxynivalenol, and nivalenol every two weeks. Nivalenol was not detected in any of the samples. Approximately five times more zearalenone than deoxynivalenol was produced at all temperatures tested. More zearalenone was produced at 16\ub0C (5-1300mg kg-1) than at 26\ub0C (5-750mg kg-1). When the fungus was grown at 16\ub0C for five weeks and transferred to 26\ub0C, production of zearalenone was stimulated. Although more deoxynivalenol was produced by the fungus at 26\ub0C (1-62mg kg-1) than at 16\ub0C (1-50 mg kg-1), most deoxynivalenol was produced by the fungus at 26\ub0C (1-62 mg kg-1) than at 16\ub0C (1-50mg kg-1), most deoxynivalenol was produced by the fungus grown at 16\ub0C for five weeks and then transferred to 26\ub0C for the next five weeks (1-137 mg kg-1). Growth of the fungus at 26\ub0C for 5 weeks before transfer to 16oC did not result in any significant rise in either zearalenone or deoxynivalenol production

Effects of Temperature on the Simultaneous Production of Zearalenone and Deoxynivalenol by Fusarium Graminearum on Maize

Fusarium graminearum (Schwabe), a fungus commonly encountered on maize ( Zea mays L) in Zambia, was analyzed for toxin production under temperature conditions prevalent during periods of high infestations. Ground maize samples were adjusted to a moisture content of 40% and inoculated with an isolate of F. graminearum. The samples were incubated at 26°C or 16°C for 10 weeks. Samples were analyzed for the toxins, zearalenone, deoxynivalenol, and nivalenol every two weeks. Nivalenol was not detected in any of the samples. Approximately five times more zearalenone than deoxynivalenol was produced at all temperatures tested. More zearalenone was produced at 16°C (5-1300mg kg-1) than at 26°C (5-750mg kg-1). When the fungus was grown at 16°C for five weeks and transferred to 26°C, production of zearalenone was stimulated. Although more deoxynivalenol was produced by the fungus at 26°C (1-62mg kg-1) than at 16°C (1-50 mg kg-1), most deoxynivalenol was produced by the fungus at 26°C (1-62 mg kg-1) than at 16°C (1-50mg kg-1), most deoxynivalenol was produced by the fungus grown at 16°C for five weeks and then transferred to 26°C for the next five weeks (1-137 mg kg-1). Growth of the fungus at 26°C for 5 weeks before transfer to 16oC did not result in any significant rise in either zearalenone or deoxynivalenol production

Role of Pigments and Tannins in the Reaction of Tan and Red Near-Isogenic Sorghum Lines to Leaf Diseases

Sorghum ( Sorghum bicolor L. Moench) plant pigments have been associated with resistance to leaf diseases and grain deterioration. Four near-isogenic pairs of tan and non-tan (red) sorghum lines were assayed for their phenolic content and evaluated for their reaction to leaf diseases along with six other sorghum lines. Leaves, stems, sheaths, glumes and seeds of mature plants were assayed for tannins, pigments, and precursors of these pigments. No tannins were detected in the various plant tissues although other genotypes can have high levels of these compounds in seed coats. The red plants (especially the glumes and sheath) were found to accumulate 3-deoxyanthocyanidins, the major pigments in sorghum, but these were absent in the tan plants. The glumes and sheath of tan plants accumulated apigenin. Near-isogenic pairs were tested for differential reactions to anthracnose ( Colletotrichum graminicola Ces.) at Tifton, Georgia and to rust ( Puccinia purpurea Cooke) at Isabella, Puerto Rico during the 1991 growing season. Tan and red isogenic pairs, which differ significantly in phenolic composition, did not show significant differences in their disease reaction. The six other sorghum lines which showed marked differences in their reaction to leaf diseases also showed differences in their phenolic composition. However, for the phenols that were analyzed, there was no correlation with resistance or susceptibility. It is proposed that tannins, pigments, and pigment precursors are not responsible for disease resistance in these genotypes

Control Of Tribolium Confusum J. Du Val By Diatomaceous Earth (Protect-It™) On Stored Groundnut ( Arachis Hypogaea ) And Aspergillus Flavus Link Spore Dispersal

Environmental and human health problems associated with the use of synthetic pesticides have prompted the demand for non-polluting, biologically specific insecticides. The current study assessed the losses caused by Tribolium confusum and its control by diatomaceous earth and the effect on Aspergillus flavus spore dispersal during storage of groundnuts. When losses due to Tribolium confusum were assessed over a period of 60 days, it was found that an increase in insect population in stored groundnuts resulted in increased weight loss of stored groundnuts. The true weight loss due to insect feeding was 0.60 g per 400 g of stored groundnuts. When diatomaceous earth (DE) was applied to groundnuts followed by the introduction of insects in a compartment (A), increased mortality of insects with increased diatomaceous earth concentration was observed. For a concentration range of 0-2.5 g DE/kg groundnut, 2.5 g/kg treatment was the most effective (only 5 surviving T. confusum adults out of 50 were recovered in samples treated with 2.5 g/kg compared to 38 adults in the control samples). Larval emergence from groundnuts treated with DE also declined with increased diatomaceous earth concentration. When groundnuts were inoculated with A. flavus spores, followed by DE application and T. confusum introduction into compartment A, the transfer of spores between inoculated groundnut samples in compartment A and uninoculated samples in compartment B was reduced. The mean A. flavus spore concentration recovered from initially sterile compartment B was1.08x103; while it was 45 in the control and in samples treated with 2.5 g/kg dosage respectively. There was a significant difference in the mean numbers of spores recovered from groundnuts in different compartments (A, B) (H = 13.99, df = 4 and P = 0.007). Thus, from this study, losses due to T. confusum on groundnuts and fungal spore transfer in storage by this insect can be minimized by the application of diatomaceous earth (Protect-IT™) to stored groundnuts