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This study aimed to characterize different Aspergillus section Flavi isolates in search for nonaflatoxigenic strains for use as biocontrol agent. A total of 434 isolates of A. flavus were isolated from soil and stored maize grain samples collected from four agroecological zones (AEZ) i.e., AEZ-A, AEZ-B, AEZ-C and AEZ-D of Khyber Pakhtunkhwa (KP) province of Pakistan. The mycological analysis of the samples demonstrated that the highest population of Aspergillus section Flavi was existed in soil (n = 236) than in maize grain samples (n = 198). Across all the four zones, the highest population of Aspergillus section Flavi was observed in AEZ-C (n = 115) whereas the lowest population was found in AEZ-B (n= 99). The isolates of Aspergillus section Flavi were then characterized for their aflatoxigenicity and nonaflatoxigenicity by cultural (i.e., production of blue fluorescence, room temperature phosphorescence, ammonium hydroxide vapor induced color change and sclerotia production) and immunological methods i.e., enzyme linked immunosorbent assay (ELISA). All the four cultural methods successfully differentiated aflatoxigenic and nonaflatoxigenic isolates, however ammonium hydroxide vapor induced test was found to be the most efficient (80.29%) for segregation of the isolates. Among all isolates, thirty were screened for their total aflatoxin production in corn meal agar medium by using ELISA technique. The results showed that isolate AFS32 produced highest level of total aflatoxin (230.78 µg Kg-1) while isolates AFS5, AFS17, AFS25 and AFS33 produced no aflatoxin. These nonaflatoxigenic isolates were considered as isolates of interest and could be used as biocontrol agent in agricultural fields for prevention of pre-harvest aflatoxins production in different crops. [ABSTRACT FROM AUTHOR]

This study investigated the influence of water activity (aw) and storage time on total fungal and Fusarium counts and mycotoxins zearalenone (ZON), trichothecenes type-A (i.e. T-2 and HT-2) and trichothecenes type-B (i.e. DON, 3-ac DON, 15-ac DON) production in maize grains. Water activity of the grains was adjusted to 0.85, 0.90 and 0.95 aw and the samples were stored at 25°C for 45 days. The control samples were kept without any aw modification. At 15 days interval, the samples were analyzed for the aforesaid parameters. The data showed that aw and storage time alone and interactively significantly (p<0.05) affected the analyzed parameters. The lowest total fungal counts (12.26×103 CFUs/g) were recorded in 0.85 aw sample at the start of storage, whereas the highest total viable counts i.e. 18.01×103 CFUs/g were documented at day 45 in the grain sample of 0.95 aw. The total Fusarium count varied from 0.42×103 CFUs/g in control sample at the start of storage time to 0.94×10³ CFUs/g at day 45 in the sample modified to 0.95 aw. The lowest ZON (855.50 µg/kg), DON (1246.45 µg/kg), 3-ac DON (234.41 µg/kg), 15-ac DON (90.58 µg/kg), T-2 (221.15 µg/kg) and HT-2 (221.24 µg/kg) were recorded at the onset of storage time in the sample of 0.85 aw, whereas these mycotoxins steadily increased and attained the highest values at the uppermost marginal values of aw and storage time. It was concluded that fungal growth and mycotoxins production in maize grains were favored by elevated aw and increasing storage time. Therefore, it is recommended that cereals grains should be kept at reduced aw to prevent fungal growth and subsequent mycotoxins production in the grains during post-harvest storage. [ABSTRACT FROM AUTHOR]

This study aimed to investigate the impact of integrated use of biochar and nitrogen (N) fertilizer on soil physicochemical properties at various growth stages of maize and subsequent wheat crop. Biochar was applied before sowing, while N application was carried out in splits to the crops. The study was conducted in district Buner, Pakistan using randomized complete block design with split-plot arrangement. Biochar was applied at the rates of 0, 5, 10, 15 and 20 ton/ha as the main plot factor. The immediate effect of biochar was assessed on maize crop integrated with four levels of N viz. 0, 100,150 and 200 kg/ha applied as sub-plot factor. The residual impact of the previously applied biochar levels coupled with fresh applications of N at the rate of 0, 80, 120 and 200 kg/ha was assessed on subsequent wheat crop grown on the same plots. The soil physicochemical properties were evaluated in the beginning, reproductive stage and at maturity of each crop. The average values of soil pH, electrical conductivity (EC), organic matter (OM), N, P and K of the soil before sowing of maize crop were found to be 8.2, 0.37 dS/m, 0.95%, 1.74 mg/kg, 3.45 mg/kg, 61.5 mg/kg, respectively. Biochar and N application significantly (p≤0.05) increased soil pH whereas soil OM was substantially enhanced only with biochar at the reproductive stage of maize. However, at this stage, the effect of biochar and N application was not significant (p≥0.05) on soil EC. At maturity stage of maize crop, soil pH, OM and EC were not significantly (p≥0.05) varied from that at reproductive stage. Residual biochar significantly (p≤0.05) increased soil pH and OM at reproductive stage of wheat. Similarly, the effect of both residual biochar and different N levels was not significant (p≥0.05) on soil EC. However, at maturity stage of wheat crop soil OM, was significantly (p≤0.05) increased with biochar residues and N applications, whereas soil pH was only influenced by residual biochar. The effect of N was not significant (p≥0.05) on soil pH and EC at maturity stage of wheat crop. As biochar improve the soil physicochemical properties therefore biochar application along with N fertilizer might be helpful in maintaining healthy soil for better crop productivity. [ABSTRACT FROM AUTHOR]

Abstract: Mould incidence and aflatoxin B1 (AFB1) and ochratoxin A (OTA) contamination as well as proximate composition and minerals content of maize kernels from Swat Valley, North West Frontier Province of Pakistan was studied during the year, 2007. Results indicated that the mean moisture content of the kernels was within the recommended safe storage levels of ⩽15%. Across the whole valley, Aspergillus, Fusarium, Penicillium and Rhizopus were the most predominant fungal genera identified and amongst the mycotoxigenic species, Aspergillus flavus had the highest incidence. AFB1 content ranged from none to 30.92μg/kg with the average values of 14.94 and 16.22μg/kg for Upper and Lower Swat regions, respectively. Similar trend was observed for OTA with the contamination level ranged from <0.001 to 7.32μg/kg. A significant numbers of samples contained AFB1 and OTA levels above the safe limits as recommended by the USFDA and EU but on the average the results were within the safe limit. These results indicate that maize consumers in Swat Valley may be exposed to the danger of aflatoxins and ochratoxins poisoning. Thus, there is a need for policy makers to establish and enforce maize quality standards and regulations related to moulds and mycotoxins across the area. [Copyright &y& Elsevier]