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  • Author or Editor: Y. Gherbawy x
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Inoculating wheat (cv. Giza 164) with various Fusarium species had different effects on the catalase (CAT), peroxidase (POX) and ascorbate peroxidase (APX) activity in different plant tissues. The CAT activity induced in the shoots of wheat plants by some pathogens (F. merismoides, F. moniliforme, F. poae and F. sambucinum) was relatively higher than that induced by other pathogens. The results showed an increase in POX activity in infected shoots except those inoculated with F. sambucinum, where the POX activity decreased. Inoculating wheat plants with individual Fusarium species or with a mixture of pathogens caused an increase in APX in the shoots, except for those treated with F. poae, where the APX activity decreased. The activity of these antioxidant enzymes thus increased in most cases in the shoot system of wheat plants under Fusarium infection. Investigations on the metabolic activity of wheat plants inouculated with individual Fusarium species or with a mixture of pathogens showed higher contents of all the protein fractions, soluble sugars, total free amino acids and proline. The K+ and Ca2+ concentrations decreased to various extents in different cases. The Na+ content increased in wheat shoots, especially after inoculation with F. merismoides. The results signify that the most serious infection was caused by F. culmorum, F. graminearum and F. oxysporum and by a mixture of all the Fusarium species.

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Alternaria species produce several mycotoxins that are of particular health concern. The natural occurrence of three Alternaria toxins; alternariol (AOH), alternariol methyl ether (AME), and tenuazonic acid (TA) in pomegranate fruit was considered. A. alternata and A. tenuissima were identified by analysis of partial sequence of ITS-region. All studied strains produced high quantities of AOH in vitro on rice. A. tenuissima produces high quantities of AME and TA compared with A. alternata. In rotten tissues AME was the highest determined toxin with frequency percentage of 95.6%, followed by AOH and TA. All toxins were detected in the healthy tissues surrounding the infected tissues but at low levels. No visible changes were noted in Alternaria toxins after pasteurization of pomegranate juice, but they appeared after clarification. In conclusion, pasteurization and/or clarification are not sufficient to reduce Alternaria toxins in juice. The removal of the rotten parts does not ensure excluding Alternaria toxins.

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