Bacterial wilt of tomato, caused by Ralstonia solanacearum (Rs), is endemic in most tomato-growing areas of Nigeria, causing 60 to 100% loss in yield. Control measure requires definite information on race and biovar characteristics of the pathogen in those endemic areas. Soil samples were collected from seven states in Nigeria known for high incidence of tomato bacterial wilt. Isolations were performed on triphenyl tetrazolium chloride (TZC) and casamino peptone glucose (CPG) media. Morphological characterization of the pathogen was through simple staining, streaming and KOH solubility test.Molecular confirmation of pathogen's identity was through PCR amplification of genomic DNA using Rs-specific 759/760 primers (f:5'-GTCGCCGTCAACTCACTTTCC-3'; r:5'-GTCGCCGTAGCAATGCGGAATCG-3').Race was determined through hypersensitive reaction on tobacco leaves and biovar characterization was through carbohydrate utilization test. Thirty-four bacterial isolates showed the characteristic creamy white colour on TZC + CPG medium. . The isolates also amplified at 280 bp, confirming the pathogen as Rs. Thirty isolates belonged to Race 1 Biovar III while four belonged to Race 3 Biovar II. The findings are relevant while devising a more targeted management approach to bacterial wilt of tomato in Nigeria.

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A preliminary survey involving limited sample size was conducted to determine the spectrum of moulds and mycotoxins in wheat grains from flour mills and local markets in Nigeria. Fourteen wheat samples were analyzed for moulds using standard mycological methods and for toxic fungal metabolites using a liquid chromatography-tandem mass spectrometric method. Fusarium (range of incidence 12.5-61.7%) dominated in the wheat grains though species of Aspergillus (range of incidence 2.24-3.86%) were also recovered from the samples. The identified fungal species were Aspergillus flavus (7.7%), Aspergillus niger clade (2.6%), Fusarium avenaceum (10.9%), Fusarium culmorum (22.4%) and Fusarium graminearum (56.4%). A total of 54 microbial metabolites were detected in the samples at concentration ranging between 0.01 μg/kg for macrosporin and 2560 μg/kg for deoxynivalenol. Among the four mycotoxins addressed by regulations in the European Union (EU) found in the samples, deoxynivalenol (incidence 100%) dominated in the samples and its levels exceeded the maximum acceptable EU limit (750 μg/kg) in 36% of the samples. This report underscores the need for more robust surveys with larger sample sizes and across several agro-ecologies in the country.

A survey was conducted in 2000 to determine the incidence of Fusarium spp and fumonisin B 1 contamination in maize in farm stores in eight areas of Ogun State, Nigeria. F. moniliforme was the predominant species, in 56% of the samples, with a mean kernel infection of 68% in positive samples. The other species in decreasing order of abundance were F. graminearum, F. pallidoroseum, F. solani and F. oxysporum. Analysis by high performance liquid chromatography (HPLC) indicated that 51% of the samples were contaminated with fumonisin B 1 , at 65 to 1830 µg/kg.

The mycoflora, moisture content and aflatoxin contamination of pigeon pea (Cajanus cajan (L.) Millisp) stored in jute sacks and iron bins were determined at monthly intervals for a year. The predominant fungi on freshly harvested seeds were Alternaria spp., Botryodiplodia theobromae, Fusarium spp. and Phoma spp. These fungi gradually disappeared from stored seeds with time and by 5-6 months, most were not isolated. The fungi that succeeded the initially dominant ones were mainly members of the general Aspergillus, Penicillium and Rhizopus. Population of these fungi increased up to the end of one year storage. Higher incidence of mycoflora and Aspergillus flavus were recorded in jute-sack samples throughout the storage period. The moisture content of stored seeds was found to fluctuate with the prevailing weather conditions, being low during the dry season and slightly high during the wet season. The stored seeds were free of aflatoxins for 3 and 5 months in jute sacks and iron bins respectively. The level of aflatoxins detected in jute-sack storage system was considerably higher than that occurring in the iron bin system. Of 196 isolates of A. flavus screened, 48% were toxigenic in liquid culture (54% from jute sacks and 41% from iron bins).