Interaction of strains of non-toxigenic Aspergillus flavus with Aspergillus parasiticus on aflatoxin production
Aflatoxins production is affected by abiotic, biotic and genetic parameters. Eugenesic and dysgenetic condition for aflatoxinogenesis are relatively well studied, such as: the influence of temperature, pH, Aw, Oxigen tension, osmotic pression, organic and inorganic nutrients, substance with fungistatic effects: however there are relatively few knowledge about endogenous regulator mechanisms, the kinetic of the anabolism and the interaction between the productive moulds and remaining microflora holding in eutrophying substrates. The main objective of this study is to evaluate biotic interaction between five indigenous strains of A. flavus, confirmed non-toxigenic, and a productive strain (A. parasiticus ATCC 15 517), cultured simultaneously on two substrates: one natural (cracked corn) and a synthetic one, modified Czapeck-Dox broth. Aflatoxins quantifications were performed by HPLC at 8th and 12th days. Results of those interactive cultures showed that all strains were synergic, increasing aflatoxins production in a range between 5.6 and 106.5% over the control values, with an exception registered on one of the strains cultured in cracked corn at the 12th day, where the production decreased (-7.6%).
Mycotoxin levels in subsistence farming systems in South Africa
Thesis (MScAgric (Plant Pathology)--Stellenbosch University, 2008. 
 
Includes bibliography.summary,list of figures and appendices.
Aflatoxin Concentration in Corn as Influenced by Kernel Development Stage and Postinoculation Temperature in Controlled Environments 1
Developing kernels' of two c:ultivan of com (Zeta mays L), 'Gaspe Flint' (Gaspe) and 'WI03 X Gaspe,' were inoculated with Aspergillus flovw Link ex Fr. at three kernel-development stages (early-dougb, medium-dougb, and. late hard-dougb) and grown in four postinoculation temperature regimes of 9.5, 12.5, 14.5, and.I7.5 C thermal units/day (mean daily temperature minus 10 C) in con· trolled envirouments. Kernels were assayed for aflatoxin B,. after plants were grown for about 865 cumulative thermal units after inoculation. The highest toxin levels (48,641 and 31,046 ppb for Gaspe and WIOS X Gaspe, respectively) were obServed in kernels inoculated at the latest kernel-development stage (late hard-dougb) and grown at the highest postinoculation temperature regime (17.5 C thermal units/day, i.e., daY/night temperatures and times of 30/26 C and 9115 hours, respectively). Toxin levels were low in kemels inoculated at earlier develop ment stages and grown at lower temperatures. Longer postinoculation growth at lower temperatures did not raise aflatoxin concentrations to levels observed with shorter postinoculation growth at higher temperatures. Additional index of to 735 ,aEm-"sec-1. be tween 400 and 700 nm plus 10 to 13 Wm- 2 of photomoryho. genic irradiance between 700 and 850 nm. as measured WIth a cosine-correlated Lamba Instruments& quantum/radiometer/pho tometer located 95 em from the lamps. Two light periods were used for growing plants before inocu lation to achie\'e the desired plant size and growth rate for each cultivar. The first was the basic photoperiod of 9 hours of high-intensity light, as described above. and was considered the short daylength. basic intensity light period plus to from densitometrically. B,. confirmed in rep resentative positive samples by the formation of water adduct B,. fit to a individual· ly and a fixed mary cant ratio (LSR) was determined as the antilogarithm of the