Papers by Medhat El-Naggar
Six different abiotic elicitors (oxalic acid, potassium oxalate, salicylic acid, Bion, Fungastop ... more Six different abiotic elicitors (oxalic acid, potassium oxalate, salicylic acid, Bion, Fungastop and Photophor) were used to study their effect on induced resistance of cucumber (Cucumis sativus L.) against powdery mildew (Sphaerotheca fuliginea) disease. The inducers efficiency was evaluated depending on disease severity calculation and measure the biochemical change in both pathogensis Related Protein (PR) and phytoalexin accumulation in treated plants comparing with the control. Pretreatment of cucumber plants with all tested elicitors recorded a decrease in powdery mildew disease severity. Bion recorded the most effective inducers (63.8 and 72.4%) while potassium oxalate recorded the lowest effective one (37.0 and 58.3%) in both single and booster spray. Induced resistance of cucumber against powdery mildew recorded an increase in PR-proteins (peroxidase, polyphenoloxidase, Chitinase and β-1, 3 glucanase) activity as well as an increase accumulation of phytoalexins. Application of abiotic agents in these experiments enhances the induced resistance in cucumber against powdery mildew. It would therefore be the proposal to use abiotic inducers as alternatives to the fungicides and one of a wide range of disease management tools.
Zearalenone (ZEA) is mycotoxin contaminants of foods and feeds and produced mainly by fungi belon... more Zearalenone (ZEA) is mycotoxin contaminants of foods and feeds and produced mainly by fungi belonging to the genus Fusarium. A polyphasic approach consisting of morphological, chemical and molecular characterization was applied on 37 isolates of different species of Fusarium. Randomly representative sample of wheat grains were collected from different areas of Saudi Arabia for isolation trials. The most of Fusarium were namely; Fusarium graminearum, F. verticilliodes, F. oxysporium, F. culmorum, F. avenaceum, F. redolen, F. solani, F. udum, F. semitectum F. chlamydosporum, F. proliferatum and F. poae. Many protocols were used to determine the ability to excrete zearalenone (ZEA) as well as identify the toxigenic Fusarium isolates as bioassay, immunoassay, chromatographic and molecular procedures. The yeast of Saccharomyces cerevisiae and Kluyveromyces marxianus were tested to differentiate between toxigenic and non-toxigenic Fusarium isolates. Also, Immuno-affinity column and auto-ELISA were used to determine the ZEA and their findings largely identical with HPLC results. The presences of the toxigenic genes is correlate with toxicity therefor polymerase chain reaction (PCR) was performed using one set of primers specifically targeted to gene of ZEA biosynthesis. The toxigenic Fusarium species reacted positively with tri5-gene specific PCR primer [d (GCT GCTCATC ACTTTGC TCAG)-3]. This specific primer gave good screening for zearalenone producers as well as primitive differentiate between toxigenic and non-toxigenic Fusarium isolates but it lacks quantification estimation. Also, it failed to put all toxigenic isolates in one group and/or sub-cluster. This detection provided importance information to predict toxigenic profiles which may be present in wheat grains. The objective of the current study found the accurate, cheap and realistic estimation of ZEA toxin contamination to appropriate strategy to detoxify and/or decontaminate this toxin.
Zearalenone (ZEA) is mycotoxin contaminants of foods and feeds and produced mainly by fungi belon... more Zearalenone (ZEA) is mycotoxin contaminants of foods and feeds and produced mainly by fungi belonging to the genus Fusarium. A polyphasic approach consisting of morphological, chemical and molecular characterization was applied on 37 isolates of different species of Fusarium. Randomly representative sample of wheat grains were collected from different areas of Saudi Arabia for isolation trials. The most of Fusarium were namely; Fusarium and F. poae. Many protocols were used to determine the ability to excrete zearalenone (ZEA) as well as identify the toxigenic Fusarium isolates as bioassay, immunoassay, chromatographic and molecular procedures. The yeast of Saccharomyces cerevisiae and Kluyveromyces marxianus were tested to differentiate between toxigenic and non-toxigenic Fusarium isolates. Also, Immuno-affinity column and auto-ELISA were used to determine the ZEA and their findings largely identical with HPLC results. The presences of the toxigenic genes is correlate with toxicity therefor polymerase chain reaction (PCR) was performed using one set of primers specifically targeted to gene of ZEA biosynthesis. The toxigenic Fusarium species reacted positively with tri5-gene specific PCR primer [d (GCT GCTCATC ACTTTGC TCAG) -3]. This specific primer gave good screening for zearalenone producers as well as primitive differentiate between toxigenic and non-toxigenic Fusarium isolates but it lacks quantification estimation. Also, it failed to put all toxigenic isolates in one group and/or sub-cluster. This detection provided importance information to predict toxigenic profiles which may be present in wheat grains. The objective of the current study found the accurate, cheap and realistic estimation of ZEA toxin contamination to appropriate strategy to detoxify and/or decontaminate this toxin.
International Journal of Plant Pathology, 2011
The Philippine Scientist
Aspergillus species associated with peanut kernel collected from Mecca, Madina, and Riyadh, Saudi... more Aspergillus species associated with peanut kernel collected from Mecca, Madina, and Riyadh, Saudi Arabia were enumerated to assess the occurrence of aflatoxigenic species in these species. Also, a polymerase chain reaction (PCR) assay was optimized to identify two major toxigenic Aspergillus species, namely, Aspergillus flavus and Aspergillus niger collected from peanut seeds. Statistical data revealed the predominance of A. flavus (48%) and A. niger (42%) in sterilized seeds. Potential ability to produce aflatoxins (AFs) B1, B2, G1 and G2 was analyzed using high-performance liquid chromatography (HPLC). Among the 28 isolates analyzed, 21 produced aflatoxins, mainly B1 and B2. A. flavus isolates produced mainly aflatoxin B1 and had various levels of toxigenicity. Some isolates of A. flavus and A. niger produced aflatoxins B1, B2, G1 and G2 while others produced some aflatoxins with concentrations ranging from 1 to 7 ppm. The dendrogram showed that all aflatoxic isolates from the two...
International Journal of Advanced Research
The feeds and their raw materials are susceptible to attackfrom many fungi that may affect them i... more The feeds and their raw materials are susceptible to attackfrom many fungi that may affect them in terms of quality and economic value. Most of these fungi have the ability to produce numerous mycotoxins. Two hundred and thirty five of fungal isolates were isolated from random samples of wheat, corn, soybeans and also feeds poultry and livestock in Saudi markets in the summer of 2012. These fungal isolates belong 22 species and/or 11 genera. The isolated fungi included 8 isolates of Aspergillus fumigatus. The fungal isolates identified by classic method and BIOLOG Inc. System. The Aspergillus fumigatus re-identified with using nucleotide sequences using ITS1 and ITS4. The resulting sequences are matched with NCBI database. The role of yeast (Saccharomyces cerevisiae) and?- D- glucan biopolymer to reduce the linear growth of tested A. fumigatus was examined on MEA media.?- D- glucan biopolymer treatment led to reduced growth between 65.43-85.6%, while the yeast reduced the growth of ...
Journal of Pure and Applied Microbiology
Cottonseed borne fungi were isolated from five cotton (Gossypium barbadense L.) cultivars; Giza-8... more Cottonseed borne fungi were isolated from five cotton (Gossypium barbadense L.) cultivars; Giza-80, Giza-86, Giza-88, Giza-90 and Giza-92. Alternaria spp., Aspergillus flavus, A. niger, Aspergillus spp. Fusarium spp., Penicillium spp., Rhizopus stolonifer and Trichoderma spp. were occurred in both non-strilized and sterilized seeds. A. niger was generally the most predominant fungus with isolation frequency range of 20.95% to 73.17%. Mycotoxin analysis were performed by high performance liquid chromatography (HPLC). HPLC analysis of cottonseed revealed the presence of mycotoxins that were varied according to storage periods and genotypes. Significant correlations between the frequency of isolated fungi and the mycotoxin production was recorded in this study. Seven models were constructed using the predictors supplied by stepwise regression with R² values ranged from 0.433 to 0.578%. Since the stepwise multiple regression was effectively constructed 7 predictive models; this study su...
Life Science Journal
The myco-contaminants associated with almond seeds were surveyed and the fungal isolation frequen... more The myco-contaminants associated with almond seeds were surveyed and the fungal isolation frequencies were statistically analyzed. HPLC was used to assess the mycotoxins production of some involved fungi. Nine species belonging to six fungal genera were recovered from a total of 20 random samples of almond collected from different locations in Riyadh, Kingdom of Saudi Arabia. Aspergillus flavus, A. niger, A. ochraceus, A. ustus, Chaetomium globosum, Penicillium aurantiogriseum, Phoma sp. Rhizopus sp. and Ulocladium atrum were isolated. A. niger was the most predominant while, C. globosum was the least frequent species. Significant positive and negative correlations were found among isolation frequencies of some isolated fungal species. About 40% of A. flavus isolates produced aflatrem (2-3 ppb), while 60% were sterigmatocystin (300-440 ppb) and maltoryzine (7-10 ppb) producers. Meanwhile, 57% of A. niger isolates were capable of producing oxalic acids (47-430 mg/ml). On the other hand, 60% of P. aurantiogriseum isolates were citrinin producers (5-22 ppb) and 40% were citrovirdin producers (20-45 ppb). Due to the ideal nutrient composition of almond, as well as inappropriate processing and storage conditions, the risk of fungal and mycotoxin contamination could be increased. To avoid almond contamination with toxigenic fungi, and prevent hazards to human and animal health; rigorous quarantine, accurate diagnosing methods and healthy storage conditions should be undertaken. [Yassin M.A, El-Samawaty A.M.A., Moslem M.A, El-Naggar M.A.
Journal of Pure and Applied Microbiology
The aim of the present work was to survey the myco-contaminants associated with pistachio nut con... more The aim of the present work was to survey the myco-contaminants associated with pistachio nut consumed in Riyadh, Kingdom of Saudi Arabia. A total of forty commercially available samples, randomly collected from different locations were investigated and the isolation frequencies of myco-contaminants were statistically analyzed. Mycotoxins productivities of the isolated fungi were analyzed using HPLC. Nine fungal species belonging to five genera were found to be associated with pistachio nut samples. Distributions of isolated fungi indicated that Aspergillus niger, Rhizopus sp. and A. flavus were predominant with isolation frequencies of 67.7%, 57.5% and 32.5% respectively. Highly significant positive and negative correlations were observed among some fungal species when compared with the frequency of the others. The mycotoxins; Aflatrem, maltoryzine and sterigmatocystin were produced by 60%, 40% and 60% of the A. flavus isolates in this study. Meanwhile, 50% of the tested A. niger isolates were oxalic acids producers. Neither citrinin nor citreoviridin could be produced by any of the tested Penicillium spp. in this study.
Organophosphorous nematicides are highly toxic pesticides used to control nematodes in agricultur... more Organophosphorous nematicides are highly toxic pesticides used to control nematodes in agriculture soil. An in vitro Biodegradation study was conducted to determine the biodegradability of, ethoprophos, fenamiphos and triazophos nematicides, using fungi strains isolated from sandy agriculture soil under date palm trees. Five fungi strains labeled as S1 (Fusarium oxysporum), S2(Aspergillus flavus), S3 (Aspergillus fumigatus), S4 (Fusarium moniliforme) and S5 (Trichothecium roseum) were isolated and identified, then incubated with nematicides at successive intervals untill 45 days in liquid medium paralleled with control samples. Recovery rates were performed at two levels 0.1 and 1 mg kg-1 , values were over 90% for all nematicides. Limit of detection values (LOD) were 0.010, 0.012 and 0.011 mg kg-1 and limit of quantitation values (LOQ) were 0.033, 0.040 and 0.036 mg kg-1 respectively. Data indicated that S1 (Fusarium oxysporum) and S2 (Aspergillus flavus) accelerated the degradation rate of all mentioned nematicise, and S2 had the highest impact more than S1, while the other strains had no significant effect. Half-life values (RL 50) for nematicides with S1 were 18.15, 16.65 and 15.24 days, respectively, and with S2 were 10.35, 13.87 and 11.18 days, respectively, while control values were 26.30, 24.28 and 26.70 days, respectively.
American Journal of Biochemistry and Molecular Biology, 2011
Airborne Aspergillus species were surveyed in outdoor environment of Riyadh city using mechanical... more Airborne Aspergillus species were surveyed in outdoor environment of Riyadh city using mechanical air sampling technique. Aflatoxin productivity rates of the obtained species were also investigated using HPLC. Aspergillii were the most predominant myco-pollutants of outdoor air in Riyadh city and intensively concentrated at Al-Murabba site. Among twenty five Aspergillus species obtained, A. niger and A. flavus were the most predominant ones. A. niger, A. flavus and E. nidulans were also highly distributed species over the sites. Surveyed Aspergillii varied in their ability to produce aflatoxins. Thus, although some species were aflatoxigenic, others exhibited no detectable toxin production. Aspergillus flavus was the highest producer of B 1 (6.6 ppb), G 1 (3.82 ppb) and G 2 (2.82 ppb) aflatoxins. Further information on genera, species and spore density in the air are limiting factors required for assessing any adverse effects of outdoor mycopollutants.
Mycoflora associated with 120 walnut samples was examined using agar plate method. Data of isolat... more Mycoflora associated with 120 walnut samples was examined using agar plate method. Data of isolation frequency were statistically analyzed. Mycotoxin productivity of obtained fungi was assayed using HPLC. Twelve species belonging to six fungal genera were isolated in this work. Aspergillus flavus, Aspergillus niger and Rhizopus stolonifer were the most predominant, with highest distribution over samples. Significant to highly significant positive correlation was found among some isolated fungi. Most of Aspergillus flavus isolates were capable of producing sterigmatocystin, maltoryzine and aflatrem. Meanwhile, all tested isolates of Aspergillus niger were capable of producing oxalic acids ranged from 300-850 mg/ml in the culture media. Both of Fusarium proliferatum and Fusarium subglutinans were toxigenic and varied in their productivities of ipomeanine, neosolaniol, nivalenol and NT-2 toxin. In respect to citrinin and citreovirdin, Penicillium aurantiogriseum was more productive than Penicillium brevicompactum.
Journal of Plant Sciences, 2011
American Journal of Food Technology, 2011
Date palm (Phoenix dactylifera L.) is considered the main crop in deserts and arid areas such as ... more Date palm (Phoenix dactylifera L.) is considered the main crop in deserts and arid areas such as Saudi Arabia. Five Streptomyces species and other fungal species were isolated from date palm rhizosphere soil of several cultivars, such as Barhi, Khalas, Sullaj, and Sukkari, in the Ghat and El-Gouf regions. Streptomyces strains were isolated on Biolog universal growth agar medium and were identified following Biolog methods. The predominant Streptomyces isolated from this present survey was S. plicatus followed by S. rimosus, S. rutgersensus, and S. griseus. The number of soilborne fungi in the tested soil decreased with the increased number of isolated Streptomyces. There was a significant positive correlation between the date palm cultivar and the number of isolated Streptomyces. The in vitro effects of isolated Streptomyces species on some toxigenic fungi were also studied. Enzyme-linked immunosorbent assay, immunoaffinity column chromatography, and high-performance liquid chromatography were used to study the mycotoxins. The concentration of most of the tested mycotoxins was reduced significantly with the presence of the Streptomyces isolates. Results indicate that some Streptomyces isolates established in date palm rhizosphere have the ability to reduce production of mycotoxins of some toxigenic fungi; thus they have the potential of reducing the subsequent disease occurrence. Therefore they can be applied in wider range as biocontrol agents.
Journal of Plant Sciences, 2012
Journal of Plant Sciences, 2012
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Papers by Medhat El-Naggar