Study On Effect Of Fusarium Infection On Fumonisin B₁ And B₂ Contamination In Asparagus Production And Analysis Of Pesticides Residue In Asparagus

Fumonisins are a group of structurally related toxic metabolites mainly produced by Fusarium vertieilliodes (formerly F.moniliforme) and Fusarium proliferatum, which frequently occurs and grows on asparagus at some regions. Fumonsins have been shown to cause several diseases in animals, such as leukoencephalomalacia in horses, pulmonary oedema and hydrothorax in swine and hepatic canceer in rats. They have also been suspected of causing oesophageal cancer in humans in regions. Incidence of Fusarium spp. in asparagus and levels of fumonisins mycotoxin in asparagus spears (edible asparagus) in two main areas (caoxian county, Shandong province and dongshan county, Fujian province) were studied. Furthermore, this study were to evaluate the effect of temperature and co-inoculation of Fusarium oxysporum on production of fumonisin B₁ and B₂ by strains of F. proliferatum on sterile maize grain and surface-disinfected asparagus spears. The results of study were as follows:In caoxian county, Shandong province, F. proliferatum and F. oxysporum were dominant species isolated from asparagus crowns sampled from eight fields, 89% and 63% of the individual crowns were infected with F. proliferatum and F. oxysporum, respectively. In dongshan county, Fujian province, F. oxysporum was the most prevalent species detected in 99% of asparagus crowns and F. proliferatum was isolated less frequently (1.3%). However, Fusarium vertieilliodes was isolated rarely from asparagus crowns in two regions.An analytical method for determination of fumonisin B₁ and B₂ in foodstuffs such as maize, asparagus by high performance liquid chromatography electrospray ionization tandem mass spectrometry was developed. In vitro, Strains of F. proliferatum isolated from asparagus crowns from caoxian county, Shandong province were studied for their capability to produce FB₁ and FB₂. All 53 strains of F. proliferatum used in this study produced FB₁ (10¹1499 mg/kg) and FB₂ (2⁶598 mg/kg) on autoclaved maize kernels. In these strains, 83% were high producers (≥500 mg/kg). On surface-disinfested asparagus spears, 96% (51) of the strains produced FB₁ (0.2⁶17.7 mg/kg) and 92% (49) of the strains produced FB₂ (0.1⁴0.3 mg/kg). But only 5.7% (3) of the strains were high producers. Their capability to produce FB₁ and FB₂ was diverse for different strains of F. proliferatum and on different medium for same a strain. Fumonisin B₁ and B₂ producing by the strains of F. priliferatum were always much higher on maize grain than on asparagus spears. There was no good correlation for their capability to produce toxins between on maize grain and on asparagus spears. All strains produced relatively high levels of FB₁ than FB₂. Most strains of F. proliferatum also produced fumonisin B₃ (FB₃) on maize grain and asparagus spears (Datas is not showed).Abiotic factors such as temperature and water activity (a_w) and of fungal interaction have an important influence on the ability of these Fusarium species to germinate, grow and produce mycotoxins in vitro and on maize grain. At certain water activity (a_w), 25℃ was optimum for production of FB₁ and FB₂ on maize grain over a 30 days period for two tested strains. Two isolates ofF. proliferatum produced more FB₁ and FB₂ at 20℃ than at 30℃. FB₁ and FB₂ produced by F. proliferatum shown a slight trend to be inhibited by F. oxysporum under almost all conditions tested. In the presence of F. oxysporum, FB₁ and FB₂ production by different strains of F. proliferatum were notsame at the different temperatures.The study was undertaken to evaluate the natural occurrence of fumonisin B₁ and B₂ in asparagus spears from caoxian county, Shandong province. For the first samples (2004.5), Fifteen samples (75%) and twelve samples (60%) were found to be contaminated with fumonisin B₁ and FB₂ at the average levels of 47.5 ng/g and 35 ng/g, respectively. For the second samples (2004.6), Twenty-four samples (80%) were found to be contaminated with fumonisin B₁ and B₂. the average of FB₁ and FB₂ in all samples were 123 and...