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Browsing Mathematics by Subject "Aflatoxin"

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    Studies on the Interaction of Arthropods, Fungi and Mycotoxin on Stored Maize Grain in Ethiopia.
    (Addis Ababa University, 2018-06-05) Kebede, Girma; Getu, Emana (Professor)
    In Ethiopia, maize (Zea mays L.) is the most important cereal crop produced and consumed by the majority of the population. High productivity and adaptability to a wide range of environment made the maize crop one of the national commodity crops to meet the food self-sufficiency program of the country. However, currently food safety issue related to postharvest arthropod infestation and associated problems put this crop under pressure. These studies were designed to know the species composition, frequency of occurrence, and abundance of stored maize grain inhabiting arthropods with particular reference to mold feeder arthropods (Sap beetles, Staphylinids and others) for designing management options for the pest and to understand the effects of their damage on potentially mycotoxin producing fungal infection and Aflatoxin contamination of stored maize grain. The studies were conducted in purposively selected Woreda of Amhara and Oromia region, Ethiopia, from August 2013 to August 2017. Random sampling method was employed for Arthropods survey. Completely Randomized Design was used for sample collection from selected Woreda of the two regions to determine the effects of insect and mold damaged maize cob on status of sap beetles and other mold feeder insects, corn ear rot types, development of detection methods for sap beetles and Staphylinids and best detection time, and the effects of arthropods on potentially mycotoxin producing fungal infection and Aflatoxin contamination. LC/MS/MS method was used to detect aflatoxin contamination in stored maize grain. It was known from the results obtained that 81 arthropods; belonging to class Insecta (87.65%), Arachnida (8.64%), and Crustaceans (3.70%) were identified. In all selected Woreda from both regions and in both years, Sitophilus spp., and Sitotroga cerealella from grain feeders; Nitidulidae spp., Mycetophagidae spp., and Drosophillidae spp., from mold feeders; Lepinotus from psocids; Tyrophagus putrescentiae from mites; Staphylinidae spp., and Dactylosternum abdominal from natural enemies associated with mold feeder arthropods and parasitic Hymenoptera from natural enemies associated with grain and grain product feeders were found to be the most frequently and abundantly encountered arthropods. In the current study, 27 species were recorded for the first time as occurring in Ethiopia. In the study on status of sap beetles and other mold feeder arthropods on pre-harvest maize cob damage types, 19 species of mold feeder arthropod occurred in association with insect and mold damaged cobs. However, only Carpophilus sp., Brachypeplus sp., Litargus balteatus LeConte, Carpophilus dimidiatus (F.), Carpophilus hemipterus (L.), and Entomobrya spp., appeared in more than 30% of insect and mold damaged cobs. Occurrence of corn ear rot types per 120 mold damaged cobs varied significantly vi (P0.05). In both regions (years), abundance of selected sap beetles and other mold feeder insects were significantly higher on insect and mold damaged cob than undamaged cob (P0.05). Moreover, in both regions (years), the mean number of selected sap beetles and other mold feeder insect per insect and mold damaged cobs were significantly (P0.05) higher for Carpophilus hemipterus (L.) and Litargus balteatus LeConte than Carpophillus dimidiatus, Typhae stercorea and Brachypeplus spp. More than four species were detected from each of the sap beetles and staphylinids using fermented maize cob and maize cob treated with fruit juice, in the study on how to detect these insect in stored maize grain ecosystem. Carpophillus hemipterus (100%, 42.11%) and Brachypeplus spp., (100%, 34.75%) were found to be the two most frequently and abundantly detected sap beetles during this experiment. Among the four identified genera of staphylinids, Atheta spp., were found to be the most frequently and abundantly detected genera (92.5%, 15.64%). Total mean number of Carpophilus hemipterus and Brachypeplus spp., per trap captured indicated that fermented maize cob and fermented banana juice mixed with fermented pineapple juice were significantly (P0.05) more effective than fermented banana and pineapple juice in detecting these insects. However, no significant difference (P˃0.05) was observed among these attractant in detecting staphylinids. Significantly (P0.05), more Carpophillus hemipterus was detected in the first two weeks. However, significantly (P0.05) more Brachypeplus spp., and Staphylinids were detected in the last two weeks. The result obtained from the effects of insects on potentially mycotoxin producing fungal infection and aflatoxin contamination in stored maize indicated that the incidence of potentially toxigenic fungi and aflatoxin contamination were significantly (P0.05) higher on insect damaged maize kernels than undamaged maize kernels and mold feeder arthropods than grain feeder arthropods (P0.05). The mean number of arthropods, grain temperature and moisture content and number of arthropod and mold damaged maize kernels were significantly (P0.05) higher on untreated seeds than Malathion treated seeds. Pearson correlation showed significant (P0.05) positive correlation between arthropod infestation and grain temperature and moisture content and number of arthropod and mold damaged maize kernels in stored maize grain. The present study concluded that the role of arthropod infestation in stored maize grain ecosystem. The role of arthropod in stored maize ecosystem include, exposing maize kernels to potentially mycotoxin producing fungal infection, providing suitable condition for the growth of fungi and vectoring fungal spores in stored maize. The present study also concluded that condition of stored grain could determine species composition of arthropods in stored maize grain ecosystem.