Palm kernel agar: An alternative culture medium for rapid detection of aflatoxins in agricultural commodities

The feasibility of using palm kernel agar (PKA) as an alternative culture medium to desiccated coconut agar (DCA), the conventional medium for the recovery of aflatoxigenic fungi from mixed cultures andthe detection of aflatoxigenic fungi and direct visual determination of aflatoxins in agricultural commodities was assessed. The medium recovered aflatoxigenic fungi in 48 h from mixed cultures andagricultural commodities in 58 h as compared to 62 h obtained for the two treatments on desiccated coconut medium. Aflatoxigenic fungi were detected in all the agricultural commodities except for onions with maize having the highest value of 13.18% (w/w) followed by melon (10.97), yam flour (10.23) and groundnut (8.52) as against 11.48, 10.0, 6.92 and 8.52% (w/w) obtained for DCA. All aflatoxigenic strains produced a characteristic yellow pigmentation on a pink background and blue or blue green fluorescence of palm kernel agar Under long wave UV light (366nm) as against the white background of DCA, which often interferes with fluorescence with corresponding yield of aflatoxins. This shows that the medium is able to efficiently detect aflatoxin production through direct visual observation of fluorescence. Palm kernel agar (PKA) can therefore be routinely used as an alternative culture medium for screening aflatoxigenic fungi and direct visual determination of aflatoxins in agricultural commodities since it is faster and has a unique pink background for easy identificatio

Effect of harvest stage and drying methods on germination and seed-borne fungi of maize (Zea mays L.) in South West Nigeria

Germination of seed and infection by seed-borne fungi of two maize varieties DMRLSR-W and DMRLSRY as affected by stage of harvest and method of drying were studied in the growing seasons of year 2002 and 2003 at the Institute of Agricultural Research and Training, Moor Plantation, Ibadan, Nigeria. The experiment was a split-plot arranged in a randomized complete block design with four replications. Ears were harvested at 30, 35, 40, and 45 days after tasselling (DAT). Extracted seeds were dried to 13-14% moisture content (i) in shade, (ii) in sun, and (iii) artificially at 45oC in a Thermax batch type seed drier. “Initial” and “final” germination tests were conducted immediately after harvest and drying, respectively. Significant higher percentage germination was associated with seeds from cobsharvested 35 DAT which were sun dried. The highest 100-seed weight was recorded in seeds from cobs harvested 45 DAT irrespective of drying method. Associated fungi were isolated by plating seeds on potato dextrose agar. Results indicated seeds from ears harvested at 30 and 35 DAT irrespective of drying method were not infected with Fusarium moniliforme, Fusarium graminearium, Botryodiplodia theobromae and Drechslera maydis. However, seed germination was significantly lower for seeds fromears harvested at 30 DAT. Aspergillus sp. were isolated from all the seeds irrespective of stage of harvest and drying method. Penicillium sp. was not isolated from any of the seeds dried artificially. Significant higher percentage germination was associated with seeds from cobs harvested 35 DAT which were sun dried. Maximum 100-seed weight was recorded in seeds from ears harvested 45 DAT irrespective of drying method

Isolation and Characterization of Ralstonia solanacearum Causing Bacterial Wilt of Tomato in Nigeria

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