الفهرس 
Acknowledgment
Isolation and identification of the causal pathogenOnly 14 pages are availabe for public view
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Abstract
Charcoal rot disease of sunflower is one of the most important diseases that attack both seedlings and adult plants causing serious losses in crop productivity and quality. Therefore, the present investigation was designed to study the causal pathogen of the disease in Assiut Governorates. Influence of some factors on the disease incidence such as reaction of certain sunflower cultivars, biological control and effect plant extracts on control of charcoal rot disease on sunflower under greenhouse conditions. Results of this study can be summarized as follows:- Macrophomina phaseolina is the causal pathogen of charcoal rot in Assiut Governorates, pathogenicity test of twenty one isolates of M. phaseolina were tested and data revealed that almost all tested isolates were able to infect sunflower plants causing reduction in number of survival plants and increased charcoal rot symptoms. The isolates varied in their pathogenic capabilities. Isolates No.7 and No.21 proved the highest death rate, it caused the highest pre- and post- emergence damping- off and charcoal rot severity, whereas isolate No.13 was the lowest one. Other tested isolates showed an intermediate effect. 2- Studies on the effect of certain antagonistic microorganisms isolated from roots and rhizosphere of sunflower plants as biocontrol against Macrophomina phaseolina the causal pathogens of charcoal rot disease of sunflower, in vitro and greenhouse conditions showed that:- 2.1. Six fungal isolates were isolated from rhizosphere and roots of sunflower plants. An isolate identified as Trichoderma harzianum, five isolates identified as T. viride. Four bacterial isolates, one isolates identified as B. subtilis, one isolate identified as B. lentus, one isolate identified as Pseudomonas fluorescens andone isolate was identified as P. acidovorans. 2.2. All the tested antagonistic fungal and bacterial isolates were able to inhibit the growth of Macrophomina phaseolina in vitro. They varied in their antagonistic effect. 2.3. Under greenhouse conditions, applications of Trichodermaharzianum, T. viride. Pseudomonasflournace and P. acidovoransseparately to soil infested with M. phaseolina significantly increased the percentages of survival plants and reduced charcoal rot severity. 3- In vitro test, extracts of (neem, spice, basil, cucumber, camphor, mint, datura, confusion, onions and garlic) at concentrations of 10 % gave a great reduction of mycelia growth of Macrophomina phaseolina. Garlic extract was the most effective plant extracts in suppressing the mycelial growth of M. phaseolina compared with other treatments. Neem extract showed the lowest effect on reduction of linear growth of M. phaseolina. 4-Application of plant extracts under greenhouse conditions by treated seeds of sunflower (Giza 102) with certain plant extracts (garlic, cucumber and datura) at concentration of 10 % significantly reduced charcoal rot disease severity compared with control. Garlic extract gave the highest reduction of charcoal rot severity 5- Fourteen sunflower cultivars and inbred lines (Giza 102, Sakha 53, Enosa, Bozoloke, L7, L16, L22, L26, L35, L36, L46, L49, L60 and L63) were evaluated for resistance to charcoal rot incited by Macrophomina phaseolina under greenhouse and field. Most of the tested cultivars and inbred lines were susceptible to charcoal rot disease caused by M. phaseolina. Giza 102 and Sakha 53 cultivars gave the lowest percentage of disease severity, while L46 lines showed the highest percentage of disease severity of charcoal rot disease. 6- The highest amount of total phenol contents in all tested sunflower cultivars was found in infected plants of sunflower Giza 102 and Sakha 53, these cultivars the most resistant. While, L46 lines showed the lowest amount of total phenol contents in infected plants, these lines the most susceptible. 7- Diseased sunflower Giza 102 and Sakha 53 cultivars showed a highest level in all determined enzymes activity (Catalase, Peroxidase and polyphenoloxidase), such cultivars are less susceptible. However, the lowest activity of enzymes found in infected sunflower L46 line, these line the most susceptible.