الفهرس 
INTRODUCTIONOnly 14 pages are availabe for public view
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Abstract
Plants are infected with many diseases, which eventually lead to a clear loss of production. Among the most important plant pathogens, microbial pathogens, especially fungi and bacteria, lead to crop losses that may reach more than 20%. No one denies that the
use of synthetic pesticides is one of the most important and even more powerful methods used to control these pathogens, but no one also denies the damages caused by this method, whether for the environment or for humans. Plants contain thousands of constituents and are valuable sources of new and biologically active molecules possessing antimicrobial property. Discovery of antifungal and antibacterial compounds in plants is an efficient way to create new pollution-free, biodegradable and ecofriendly pesticides. Many plants have antimicrobial activities that are related to their antimicrobial constituents, including alkaloids, terpenes, polysaccharide, esters, ketones, and quinones. Effective components extracted from plants have promising potential for this purpose because of their high efficacy, low toxicity, and selective characteristics. The plants bioactive components can be used as a source of new pesticides to get the advantages in the field of pesticides against some fungi and bacteria as a trial to decrease using synthetic pesticides. The work performed in this thesis could be organized into the following three parts 1. Collection and identification of plant materials 2. Preparation and identification of the tested crude extracts 3. Biological activity measurements 4. GC-MS identification of the whole chemical contents in two active crude extracts Eight plant species namely Acokanthera spectabilis (winter sweet), Prunus armeniaca (Apricot), Mangifera indica (Mango), Punica granatum (pomegranate), Allium sativum (Garlic), Zygophyllum album and Ipomea carnea fruits were used in this study. Several results were obtained from this work as follow: 1. Fungicidal activity measurements 1.1. Fungicidal activity of the original tested plant crude extracts. The results of this point are summarized as Allium sativum (leaves) extract was higher effective against the hyphal growth of Rhizoctonia solani followed by Phytophthora infestans, Alternaria alternata and Fusarium oxysporum in descending order, in comparison with azoxystrobin which was effective against Fusarium oxysporum followed by Phytophthra infestans, R. solani and A. alternata. Hence, A. sativum (leaves) extract can be used as natural safe fungicide against Rhizoctoni solani, <81 Phytophthora infestans, Alternaria alternata and F. oxysporum, respectively in descending order of activity. P. infestans was highly sensitive to S. oleraceus (leaves) extracts and A. spectobilis. A. alternata was highly sensitive to be inhibited with S. oleraceus (leaves) extracts. The activity of the crude plant extracts was different according to the extracted parts. It was found that, the fruit extracts of A. spectabilis proved to be more active against the hyphal growth of all the tested fungi than the leaves extract of the plant. The seeds extract of I. carnea highly inhibited the hyphal growth of P. infestans and R. solani, whereas seed coat extract of I. carnea was effective against the hyphal growth of A. alternata and F. oxysporiun. 1.2. Fungicidal activity of the plant extracts fractions As a general conclusion, we can say that all fractions of P. armeniaca and Z. album from the different solvents were less effective against the hyphal growth of all the tested fungi in comparison with their original extracts, except the fraction of P. armeniaca from hexane which was more effective against hyphal growth of Fusarium oxysporum. A. alternata was much less susceptible to all the tested fractions of both P. armeniaca and Z. album. It is clear that all the fractions of Z. album were less effective than the fraction of P. armeniaca against all the tested fungi. 1.3. Fungicidal activity of plant extracts combination with the standard fungicide, azoxystrobin Due to the harmful effect that can be caused by the extensive use of pesticides, whether by repeated use or high doses, the goal of making a combination of plant extracts with the fungicide in order to increase the efficiency of the plant extract as well as reduce the used dose of the synthetic fungicide. Six combinations of five crude extracts and the standard fungicide azoxystrobin on the tested fungi F. oxysporium, R. solani, P. infestans and A. alternata were done. The interaction between the plant extracts and azoxystrobin were positive to inhibit the hyphal growth of the tested fungi. The effect of half dose of both tested extract and the standard fungicide was clear that P. infestans was the most sensitive fungus since this combination of the five plant extracts gave complete inhibition of growth. F. oxysporum ranked second in terms of its sensitivity to this combination, with an inhibition rate that ranged between 49.4% and 76.5%. A. alternata occupied the last place in sensitivity to this combination, with an inhibition rate that did not exceed 50%.