الفهرس 
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Abstract
SUMMARY
Wheat (Triticum aestivum L. em Thell.) is an important cereal crop in Egypt and all over the world. Powdery mildew, caused by B. graminis f. sp. tritici, is one of the most serious diseases of wheat worldwide. The present work designed to control powdery mildew disease of wheat plants through the application of nanoparticles, bioagents and chemical inducers of plant resistance.
The main findings of the study could be summarized as follows:
1. Survey for wheat powdery mildew in Egypt during growing season 2013-2014 indicated the presence of the disease, on different wheat cultivars, i.e. Gemmiza-10, Sakha-93, Misr-1 and Sids-12, grown at 10 different locations in Egypt i.e., Sharkia, Beheira, North Sinai, Giza and Fayoum. Under natural field infection, all these local wheat cultivars were susceptible to powdery mildew however, Misr-1 followed by Gemmiza-10 showed the highest susceptible response. The highest disease severity was recorded in Beheira and Giza governorates on Gemiza 10 and Misr 1 cultivars.
2. A total of 49 fungal and bacterial isolates were obtained from wheat rhizosphere and phyllosphere. The isolated fungi were identified as T. harzianum, T. viride and T. hamatum. However, the highest percentages of isolated fungi were T. harzianum and T. viride. The bacterial isolates were identified as B. subtilis, B. brevis, P. fluorescens, P. putida, P. polymyxa and S. griseus.
3. Nanoparticles of silicon and titanium were biologically synthesized, from these fungal and bacterial isolates, using standardized technique. Transmission electron microscopy (TEM) showed that the antagonistic fungi and bacteria synthesized silicon nanoparticles (SiNPs) and titanium nanoparticles (TiNPs). Large variations in particle size were observed and average diameter ranged 1.52– 51.67nm.
4. Control of powdery mildew (Greenhouse)
4.1. All tested isolates of antagonistic fungi significantly reduced powdery mildew disease of wheat plants. The highest reduction of disease severity was obtained with T. harzianum (ThFT1), T. hamatum (TmSA2) and T. viride (TvGK2) which reduced disease severity by 78.2, 73.0 and 71.8% respectively. Meanwhile, other isolates showed moderate effect.
4.2. All tested isolates of antagonistic bacteria significantly reduced powdery mildew disease of wheat plants. The highest reduction of disease severity was obtained with P. putida isolate (PpFT1) and B. subtilis (BsBN3) which reduced the powdery mildew severity by 78.2 and 69.2%, respectively, followed by P. putida (PpQK2 and PpSS3) which reduced disease severity by 66.6 %.
4.3. All tested concentrations of SiNPs synthesized by Trichoderma spp. isolates significantly reduced powdery mildew disease of wheat plants. The most effective treatments were SiNPs at concentration of 150 ppm synthesized by T. harzianum, T. hamatum and T. viride which reduced disease severity by 82.0, 78.2 and 76.9% respectively. Meanwhile, other concentrations showed moderate effects.
4.4. All tested concentrations of SiNPs synthesized by bacterial isolates significantly reduced powdery mildew disease of wheat plants. The most effective treatments were SiNPs at concentrations of 100 and 150 ppm synthesized by P. putida (PpFT1) and B. subtilis (BsBN3) at concentrations of 50, 100 and 150ppm which reduced disease severity by 83.3, 89.7, 84.6, 84.6 and 91.0% respectively. Also, SiNPs synthesized by P. fluorescens (PfBN1) and S. griseus (SgBN2), at concentrations of 150 ppm, reduced disease severity by 79.5 %.
4.5. All tested concentrations of TiNPs, synthesized by Trichoderma spp. isolates, significantly reduced powdery mildew disease of wheat. The most effective treatments were TiNPs synthesized by T. harzianum at concentrations of 100 and 150 ppm, T. hamatum at 150 ppm and T. viride at 150 ppm which reduced disease severity by 78.2, 80.7, 76.9 and 75.6 %, respectively.
4.6. The highest disease reduction was due to treatment with TiNPs synthesized with P. putida at concentration of 150 ppm which reduced severity of powdery mildew disease by 93.5 %, followed by TiNPs synthesized by P. putida (PpFT1) at 100 ppm, B. subtilis (BsBN3) at 150 ppm and S. griseus (SgBN2) at 150 ppm which reduced the severity of powdery mildew disease by 84.6, 80.7 and 78.2 % respectively.
4.7. All tested concentrations of methyl jasmonate and arginine significantly reduced powdery mildew disease of wheat plants. The highest reduction was obtained with methyl jasmonate at concentration of 20 mM which reduced disease severity by 85.9%. Methyl jasmonate at concentration of 10 mM and arginine at 20 mM also reduced powdery mildew severity by 80.7 and 82.0%, respectively.
5. Control of Powdery Mildew (Field Study)
A: First Location at Gelbana (North Sinai) during season 2015/2016
5.1. The most effective treatments were SiNPs and TiNPs synthesized by P. putida (PpFT1) and B. subtilis (BsBN3) which reduced the disease severity by 92.3, 92.3, 96.9 and 92.3 % respectively. Followed by SiNPs and TiNPs synthesized by T. harzianum (ThFT1), T. hamatum (TmSA2), T. viride (TvGK2) and P. fluorescens (PfBN1). Also, methyl jasmonate and arginine reduced disease severity more than 81.5% as compared with untreated plants. Meanwhile, other treatments had moderate effect.
5.2. The highest reduction was also obtained with SiNPs and TiNPs synthesized by P. putida (PpFT1) and B. subtilis (BsBN3) in addition to, methyl jasmonate which reduced the area under disease progress curve (AUDPC) by 89.3, 87.7, 88.1, 88.5 and 83.2 % respectively. Treatments by SiNPs and TiNPs synthesized by T. harzianum (ThFT1), T. viride (TvGK2), T. hamatum (TmSA2) and P. fluorescens (PfBN1) reduced AUDPC more than 81.3% as compared with untreated plants.
5.3. All tested control treatments significantly increased the growth parameters i.e. fresh weight of plant (g) and Spike weight (g). The highest increase was obtained with SiNPs and TiNPs bio-synthesized by all tested bioagents as well as fungicide diniconazol while, other treatments had moderate effect.
5.4. The highest increase was obtained with SiNPs and TiNPs bio-synthesized by P. putida (PpFT1), B. subtilis (BsBN3) and TiNPs bio-synthesized by P. polymyxa (PbBB2) which increased the grain yield more than 211.8 %. Treated wheat plants with SiNPs bio-synthesized by T. harzianum (ThFT1), T. viride (TvGK2) and T. hamatum (TmSA2) resulted in significant increase of grain yield as well as fungicide diniconazol.
B: Second location at Nubaria (Beheira) during seasons 2015/2016 & 2016/2017
5.5. The most effective treatments were SiNPs and TiNPs bio-synthesized by P. putida (PpFT1) and B. subtilis (BsBN3) which reduced disease severity by 86.5, 87.8, 90.5 and 87.8 % respectively, followed by methyl jasmonate 82.4% as compared with untreated plants. Meanwhile, other treatments had moderate effect.
5.6. The highest disease reduction was obtained with SiNPs and TiNPs synthesized by P. putida (PpFT1) and B. subtilis (BsBN3) which reduced the area under disease progress curve (AUDPC) by 88.1, 84.9, 90.6 and 85.9% respectively, followed by SiNPs and TiNPs synthesized by T. harzianum (ThFT1), T. hamatum (TmSA2) and P. fluorescens (PfBN1). Methyl jasmonate and arginine also reduced area under disease progress curve (AUDPC) more than 71.8 %. On the other hand, the results showed that the fungicide diniconazol reduced the area under disease progress curve (AUDPC) by 88.1 %.
5.7. All tested treatments significantly increase wheat growth parameters i.e. fresh weight of plant (g) and Spike weight (g). The highest increase was obtained with SiNPs and TiNPs bio-synthesized by T. viride (TvGK2), T. hamatum (TmSA2) and P. putida (PpFT1) as well as fungicide diniconazol.
5.8. All tested treatments significantly increase hundred grain weight (g) and grain yield ton/feddan. The highest increase was obtained with SiNPs and TiNPs bio-synthesized by T. viride (TvGK2), B. subtilis (BsBN3) and P. polymyxa (PbBB2). Treated wheat plants with SiNPs or TiNPs bio-synthesized by T. harzianum (ThFT1), T. hamatum (TmSA2) and P. fluorescens (PfBN1) also increased grain yield as well as fungicide diniconazol.
6. Biochemical changes, in wheat plants, associated with control treatments:
6.1. The most effective treatments were SiNPs and TiNPs synthesized by P. putida (PpFT1) and B. subtilis (BsBN3) which increased the peroxidase activity by 191.7, 208.3, 216.7 and 200.0%, respectively. Followed by SiNPs and TiNPs synthesized by T. harzianum (ThFT1), T. viride (TvGK2) and P. fluorescens (PfBN1) in addition to, methyl jasmonate which increased the peroxidase activity more than 133.3% as compared with untreated plants.
6.2. All tested treatments significantly increased the polyphenol oxidase activity. The highest increased was obtained with SiNPs and TiNPs synthesized by P. putida (PpFT1) and B. subtilis (BsBN3) which increased the polyphenol oxidase activity by 173.3, 166.7, 153.3 and 146.7% respectively. Followed by nano silicon and titanium synthesized by T. harzianum (ThFT1), in addition to, methyl jasmonate which increased the polyphenol oxidase activity by 120.0, 133.3 and 113.3 % as compared with untreated plants.
6.3. The highest increased was obtained with SiNPs and TiNPs synthesized by P. putida (PpFT1), B. subtilis (BsBN3) and T. harzianum (ThFT1) in addition to, methyl jasmonate which increased the chitinase activity more than 245.0 %.
6.4. The highest increased was obtained with SiNPs and TiNPs synthesized by P. putida (PpFT1), B. subtilis (BsBN3) and T. harzianum (ThFT1) in addition to, methyl jasmonate which increased the total protein more than 100.0 % as compared with untreated plants. Meanwhile, other treatments had moderate effect.
6.5. All applied treatments significantly increased the total phenols in wheat leaves. The highest increase was obtained with SiNPs and TiNPs synthesized by P. putida (PpFT1) and B. subtilis (BsBN3) which increased total phenols by 228.6, 257.1, 271.4 and 250.0 % as compared with untreated plants.