Survey covering 120 wheat fields was conducted in three wheat-growing districts of Kenya during the 2008 cropping season to determine the incidence of Fusarium head blight (FHB) and T2-toxin contamination in grain. FH...Survey covering 120 wheat fields was conducted in three wheat-growing districts of Kenya during the 2008 cropping season to determine the incidence of Fusarium head blight (FHB) and T2-toxin contamination in grain. FHB incidence was determined as the number of blighted ears per 10m2. Information gathered included wheat production practices, rainfall and temperature data. Fungal pathogens were isolated from wheat stems, heads, straw, grains and soil and identified based on cultural and morphological characteristics. Wheat grain samples were analyzed for T2-toxin by competitive Enzyme Linked Immunosorbent Assay (ELISA). High FHB incidences of up to 88% were recorded. Fungal genera isolated included Fusarium, Epicoccum, Trichoderma, Alternaria and Penicilium. Wheat plant parts with high infection with Alternaria and Epicoccum had corresponding low levels of Fusarium spp. Whereas Fusarium spp. were the most common fungal pathogens in stems, heads and soil, Epicoccum was frequently isolated from straw and grains. Fusarium speciesisolated included F. poae, F. graminearum, F. stilboides, F. verticilloides, F. fusarioides, F. tricinctum and F. heterosporum with F. poae and F. graminearum accounting for approximately 40% of all Fusarium infections. T-2 toxin was detected in all the grain samples and varied from 3 to 22 ppb. The study showed that FHB and T2-toxin are prevalent in the study districts and the high diversity of Fusarium species implies a challenge in FHB management as well as a risk of chronic T2-toxin exposure to humans and livestock.展开更多
A study was carried out to isolate and screen actinomycetes for antimicrobials from Menengai Crater in Kenya. The actinomycetes were isolated using starch casein agar, Luria Bertani agar and starch nitrate agar. Prima...A study was carried out to isolate and screen actinomycetes for antimicrobials from Menengai Crater in Kenya. The actinomycetes were isolated using starch casein agar, Luria Bertani agar and starch nitrate agar. Primary screening for antagonism was carried out using perpendicular method while secondary screening was done using agar disk technique. Extraction of the antimicrobials was carried out using ethyl acetate. Sensitivity testing of the crude extracts against Staphylococcus aureus, Bacillus subtilis, Escherichia faecalis, Escherichia coli, Klebsiella pneumoniae, Salmonella typhi, Xanthomonas campestris, Erwinia carotovora, Candida albicans, Alternaria alternate and Fusarium oxysporum was carried out using agar well technique. Biochemical tests and carbon source requirements were used in characterization of the selected antimicrobial producers. M1 was the best agar medium for isolation of actinomycetes. The number of actinomycetes from regions A, B, C, and D in the crater varied significantly (F = 27.50 P = 0.000). Out of the 156 actinomycetes isolates, 20 isolates were positive for both primary and secondary screening for antimicrobials. There was no significant difference in the zones of inhibition in primary screening of the actinomycetes for antagonistic properties against the test pathogens (F = 1.6957 P = 0.0838). The zones of inhibition after secondary screening varied significantly (F = 2.4473 P = 0.0089). Likewise, there was a significant difference (F = 6.6046 P = 0.001338) in the zones of inhibition after exposing the pathogens to ethyl extracts of the selected antagonistic actinomycetes. There is need to purify and characterize the antimicrobials obtained from the present study.展开更多
文摘Survey covering 120 wheat fields was conducted in three wheat-growing districts of Kenya during the 2008 cropping season to determine the incidence of Fusarium head blight (FHB) and T2-toxin contamination in grain. FHB incidence was determined as the number of blighted ears per 10m2. Information gathered included wheat production practices, rainfall and temperature data. Fungal pathogens were isolated from wheat stems, heads, straw, grains and soil and identified based on cultural and morphological characteristics. Wheat grain samples were analyzed for T2-toxin by competitive Enzyme Linked Immunosorbent Assay (ELISA). High FHB incidences of up to 88% were recorded. Fungal genera isolated included Fusarium, Epicoccum, Trichoderma, Alternaria and Penicilium. Wheat plant parts with high infection with Alternaria and Epicoccum had corresponding low levels of Fusarium spp. Whereas Fusarium spp. were the most common fungal pathogens in stems, heads and soil, Epicoccum was frequently isolated from straw and grains. Fusarium speciesisolated included F. poae, F. graminearum, F. stilboides, F. verticilloides, F. fusarioides, F. tricinctum and F. heterosporum with F. poae and F. graminearum accounting for approximately 40% of all Fusarium infections. T-2 toxin was detected in all the grain samples and varied from 3 to 22 ppb. The study showed that FHB and T2-toxin are prevalent in the study districts and the high diversity of Fusarium species implies a challenge in FHB management as well as a risk of chronic T2-toxin exposure to humans and livestock.
文摘A study was carried out to isolate and screen actinomycetes for antimicrobials from Menengai Crater in Kenya. The actinomycetes were isolated using starch casein agar, Luria Bertani agar and starch nitrate agar. Primary screening for antagonism was carried out using perpendicular method while secondary screening was done using agar disk technique. Extraction of the antimicrobials was carried out using ethyl acetate. Sensitivity testing of the crude extracts against Staphylococcus aureus, Bacillus subtilis, Escherichia faecalis, Escherichia coli, Klebsiella pneumoniae, Salmonella typhi, Xanthomonas campestris, Erwinia carotovora, Candida albicans, Alternaria alternate and Fusarium oxysporum was carried out using agar well technique. Biochemical tests and carbon source requirements were used in characterization of the selected antimicrobial producers. M1 was the best agar medium for isolation of actinomycetes. The number of actinomycetes from regions A, B, C, and D in the crater varied significantly (F = 27.50 P = 0.000). Out of the 156 actinomycetes isolates, 20 isolates were positive for both primary and secondary screening for antimicrobials. There was no significant difference in the zones of inhibition in primary screening of the actinomycetes for antagonistic properties against the test pathogens (F = 1.6957 P = 0.0838). The zones of inhibition after secondary screening varied significantly (F = 2.4473 P = 0.0089). Likewise, there was a significant difference (F = 6.6046 P = 0.001338) in the zones of inhibition after exposing the pathogens to ethyl extracts of the selected antagonistic actinomycetes. There is need to purify and characterize the antimicrobials obtained from the present study.