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Articles by G.M. Riungu
Total Records ( 2 ) for G.M. Riungu
  J.W. Muthomi , G.M. Riungu , J.K. Ndung`u , R.D. Narla , J.K. Gathumbi and J.M. Wagacha
  The study was carried out during the 2006 cropping season in Nakuru district, Kenya. Incidence and severity of head blight were determined and pathogens isolated from diseased wheat heads, wheat and maize kernels. Mycotoxin deoxynivalenol content in grain was determined by direct competitive Enzyme-Linked Immunosorbent Assay (ELISA). Pathogenicity of different Fusarium species isolated from wheat was determined by inoculation onto wheat ears in greenhouse. Head blight was highly prevalent (90-100%) and mean incidence and severity ranged from 4 to 9% and 15 to 37%, respectively. Fusarium was most prevalent in infected wheat heads while Epicoccum was most prevalent in harvested wheat grain. Only Fusarium spp. and Penicillium spp. contaminated harvested maize grain. The most frequently isolated Fusarium species were F. poae, F. graminearum and F. chlamydosporum in wheat and F. verticilloides in maize. Most wheat and maize grain samples were contaminated with mycotoxin (DON), with concentration ranging from 0-1,200 and 0-4,600 µg kg-1, respectively. Fusarium graminearum isolates were highly pathogenic, significantly reducing kernel weight. The results suggest that head blight in Nakuru district is due to a complex of Fusarium species with F. graminearum being the major pathogen. Cross-contamination of wheat and maize is implied, indicating possible contamination of wheat maize products with deoxynivalenol mycotoxin.
  G.M. Riungu , J.W. Muthomi , R.D. Narla , J.M. Wagacha and J.K. Gathumbi
  Laboratory and green house studies were conducted at the Faculty of Agriculture, University of Nairobi, to evaluate the efficacy of Epicoccum sp., Alternaria sp., Trichoderma sp. and Bacillus sp. in control of Fusarium head blight of wheat caused by F. graminearum. Fungicides folicur® and copper oxychloride were used as standard checks. Laboratory assay was carried out by paired cultures and antagonism was measured as reduction in pathogen colony diameter. Green house experiments involved dual inoculation of pathogen and antagonist onto wheat ears and head blight severity and grain yield determined. Doxynivalenol content in the resulting grain was determined by competitive direct ELISA. The antagonists and fungicides significantly reduced the growth of Fusarium graminearum colonies in culture. Folicur® and copper oxychloride completely inhibited the growth of the pathogen while Trichoderma sp. showed 64% colony growth reduction. However, the antagonists showed limited reduction in head blight severity in green house trials. Trichoderma sp. reduced head blight severity by 18% while folicur® reduced the disease by 28%. All the antagonists had little or no significant effect on grain yield. Only folicur®, copper oxychloride and Alternaria sp. reduced DON in grain by 76 to 93%. Obtained results indicate that microbial antagonists may offer potential benefit in FHB management and screening of more antagonists both under controlled and field conditions is necessary.
 
 
 
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