Tritrophic interaction between the Mexican sunflower, the aphid Aphis gossypii and natural enemies in a greenhouse experiment

The establishment of invasive plants negatively affects natural environments. Invasive herbivores that attack weeds can be used as a form of biological control, but natural enemies of herbivores must be associated with this interaction to prevent the invasive phytophagous from become a local pest. We performed a greenhouse experiment to evaluate how the cotton aphid, Aphis gossypii, a ok and invasive herbivore, affects the performance of the weed Tithonia diversifolia, the Mexican sunflower. We also examined the relationship between the aphid and local natural enemies. Seedlings of T. diversifolia were divided in two groups: one infested by the aphid and another not infested. After 22 days, we assessed the relationship between aphid abundance and the presence of natural enemies (Coccinelidae and Aphidius platensis) on infested plants, and compared the vegetative performance of the two seedling groups. Both natural enemies were positively related to high aphid density on infested plants. Plants infested by the aphid presented foliar necrosis and senescence, and a reduction of around 50% in leaf number, foliar area, shoot length and shoot, root and total plant weight compared to non-infested plants. These results indicate potential biological control of Mexican sunflower seedlings by the cotton aphid, and control of this aphid by the studied natural enemies.

Enhancing inulinase yield by irradiation mutation associated with optimization of culture conditions

A new inulinase-producing strain was isolated from rhizosphere soils of Jerusalem artichoke collected from Shihezi (Xinjiang, China) using Jerusalem artichoke power (JAP) as sole carbon source. It was identified as an Aspergillus niger strain by analysis of 16S rRNA. To improve inulinase production, this fungus was subjected to mutagenesis induced by ⁶⁰Co γ-irradiation. A genetically stable mutant (designated E12) was obtained and it showed 2.7-fold higher inulinase activity (128 U/mL) than the parental strain in the supernatant of a submerged culture. Sequential methodology was used to optimize the inulinase production of stain E12. A screening trial was first performed using Plackett-Burman design and variables with statistically significant effects on inulinase bio-production were identified. These significant factors were further optimized by central composite design experiments and response surface methodology. Finally, it was found that the maximum inulinase production (185 U/mL) could be achieved under the optimized conditions namely pH 7.0, yeast extract concentration of 5.0 g/L, JAP concentration of 66.5 g/L, peptone concentration of 29.1 g/L, solution volume of 49.4 mL in 250-mL shake flasks, agitation speed of 180 rpm, and fermentation time of 60 h. The yield of inulinase under optimized culture conditions was approximately 1.4-fold of that obtained by using basal culture medium. These findings are of significance for the potential industrial application of the mutant E12.

Distribution of aflatoxins and micro organisms in peanut and sunflower seed products and their potential health Hazards

Aflatoxins are mould metabolites of Aspargillus flavus and parasiticus that contaminate foodstuffs stored in warm moist places. These toxins are hepatotoxic and produce hepatocellular carcinoma in animals and man. To determine the presence of aflatoxins and microorganisms in ready to consume products of peanuts and sunflower seeds of an edible oil processing factory. Five hundred grams each of peanut kernels, peanut pellets, sunflower seed pellets, peanut oil and sunflower seed oil produced by a local oil extracting factory were supplied for extraction and estimation of aflatoxins and microorganisms like Salmonella, Escherichia coli [E.coli], Bacillus and Moulds. Aflatoxins B[1], B[2], G[1] and G[2] were extracted in chloroform and concentration was measured using silica gel columns. The quantitative estimation of these aflatoxins B[1], B[2], G[1] and G[2] was done by fluorescence evaluation on Thin Layer Chromatograms. All test samples contained four types of aflatoxins. The highest aflatoxin values were seen in the pellets and lowest in refined oils. All samples contained higher content of aflatoxins B[1] and B[2] than G[1] and G[2]. Refined peanut oil contained much lower aflatoxin than the sunflower seed oil. This study has also identified the presence of several types of microorganisms such as Salmonella, E. coli, Bacillus and Moulds in ready to eat peanut and sunflower seed products. Detection of high levels of aflatoxins and microorganisms in ready to eat food stuff should be a concern for food regulatory agencies since these products are consumed daily by the common man and their cumulative effect on the body might be adding to liver cancer in the population. Food regulatory agencies should regularly carry out thorough surveillance on food stuff

Comparative study of the major Iranian cereal cultivars and some selected spices in relation to support Aspergillus parasiticus growth and aflatoxin production

Aflatoxins are toxic fungal metabolites enable to contaminate a wide range of natural substrates. This contamination can be host-specific for different plant species. In this study, the ability of a toxigenic Aspergillus parasiticus to produce various aflatoxins on major Iranian cereals was evaluated with special focus on plant susceptibility to toxin production at cultivar level. Aspergillus parasiticus cultured on major Iranian cereal cultivars and some selected spices was incubated in shaking condition at 28?C for 6 days. The concentration of aflatoxins B1 and total [B1, B2, G1 and G2] was measured by thin layer chromatography. The amounts of aflatoxin B1 produced on maize, wheat and rice cultivars were in the ranges of 1.0-33.9, 41.9-193.7, and 39.1-82.3 micro g/g fungal weight, respectively. Interestingly, genetically modified Bacillus thuringiensis rice [GM rice] of Tarom Molaii cultivar examined for the first time in this study showed less susceptibility to aflatoxin production in comparison with its normal counterpart [P < 0.05]. The mean of aflatoxin production on maize cultivars was less than both wheat and rice cultivars that indicates considerable resistance of maize to aflatoxin compared with two other cereals. Unlike to Cuminum cyminum, both Helianthus annuus and Carum carvi seeds were highly resistant to aflatoxin production. These results indicate that inter- and intra-species differences exist in susceptibility of the major Iranian cereals as well as spices tested to A. parasiticus growth and aflatoxin production. Further studies are recommended to determine resistance markers of selected cultivars of Iranian cereals

effects of fungal infection of sunflower heads on the yield and characteristics of oil

Several types of fungi [Rhizopus arrhizus, Alternaria alternata, Aspergillus spp. and Botryodiplodia theobromae] were detected and found to infect sunflower heads [Meiak var.]. The infection affected the yield and characteristics of the oil. The quality of seeds was negatively affected by intense infection. Chemical analysis of seeds showed higher values of moisture and ash contents in the highly infected seeds. Yield of oil decreased by more than 16% in the severely infected samples which also showed higher contents of free fatty acids, higher peroxide values and lower iodine values. Gas chromatographic analysis showed that the concentration of total saturated fatty acids was significantly increased, while total unsaturated fatty acid considerably decreased with the progress of the infection

Susceptibilidad de variedades de híbridos de girasol a la formación de aflatoxinas / Susceptibility of sunflower varieties and hybrids to the production of aflatoxin

Habiéndose comprobado que las semillas de girasol en nuestro país presentaban contaminación con aflatoxinas se realizó un estudio sobre 4 variedades y 11 híbridos para determinar grados de resistencia a la formación de aflatoxinas al ser inoculadas experimentalmente con la cepa A. parasiticus NRRL 2999