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Articles by Mohamed A. Yassin
Total Records ( 2 ) for Mohamed A. Yassin
  Medhat A. El-Naggar , Muneera D.F. Alkahtani , Mohamed A. Yassin and Kadry M. Morsy
  Downy Mildew (Plasmopara viticola) is a well characterized plant pathogen which is known to infect a large number of grape cultivars (Vitis spp.). Downy mildew affects all parts of the plant, including leaves, shoots, buds, stems and fruit, leading to significant decreases in crop quality and on occasions complete loss of yield. This study investigates the ability of three bio-elicitors namely; Trichoderma harzianum, Streptomyces plicatus and Pseudomonas fluorescens to induce elevated levels of resistance in cv. Tifey cultivars in the face of P. viticola infection. In addition the study will explore some of the specific biochemical changes occurring within the plant in response to treatment with particular bio-elicitors with particular focus on changes in protein expression and levels of photosynthetic pigments. Enzyme activities such as peroxidise, polyphenoloxidase, chitinase and β-l, 3 glucanase were determined using spectroscopic methods, photosynthetic pigment level were determined in a similar manner. Protein expression patterns were analysed by polyacrylamide gel electrophoresis (SDS PAGE). The greatest reduction for disease severity was observed in response to treatment with T. harzianum at 1x10-6 spore mL-1 and followed by S. plicatus at 1x10-8 CFU mL-1. Both chlorophyll and carotene levels were increased in response to treatment with T. harzianum followed by P. fluorescens when compared to an infected untreated control. Significant diversity was observed in terms of enzyme activity depending on the type of elicitor employed. SDS PAGE analysis for grape seedlings showed considerable diversity in protein expression levels between biotic treatments. Pearson cluster analysis showed that protein expression patterns for treatments with S. plicatus and P. fluorescence treatment were highly similar (95.76%), T. harzianum (94.25%) clustered separately to S. plicatus and P. fluorescence indicating a possible differential response to fungal and bacterial elicitors. This study suggests that the use of bio-elicitors may provide an effective alternative to fungicides in the quest to control downy mildew disease in grapes.
  Abd El-Rahim M.A. El-Samawaty , Moawad R. Omar , Medhat A. El-Naggar , Mohamed A. Yassin and Osama E. Amer
  To determine the involvement of seed born fungi in cotton seedlings damping-off, 39 isolates representing 13 species belonging to seven genera were isolated from seven cotton cultivars and tested on the same cultivars under greenhouse conditions. Obtained results showed that cotton seedling damping off was varied among cultivars as well as within the same cultivar. The occurrence of damping off was dependent upon cultivars responsibility and the virulence of isolate used. It was also found that some tested isolates i.e., Fusarium moniliforme isolate No. 11, Fusarium semitectum isolate No. 20, Macrophomina phaseolina isolate No. 25, Penicillium isolate No. 30 and all tested isolates of Rhizoctonia were capable of infecting all tested cultivars. Tested isolates of Macrophomina phaseolina were highly virulent against different cotton cultivars.
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