Bacterial control of pathogenic fungi isolated from some wild plants in Taif Governorate, Saudi Arabia

Twenty two plants were collected from Taif Governorate, Saudi Arabia and identified. Pathogenic fungi were isolated from some of these plants and identified as Alternaria alternata, Cephalosporium madurae, Cladosporium herbarum, Fusarium oxysporum, Humicola grisea, Penicillium chrysogenum, and Ulocladium botrytis. Three antagonistic bacterial isolates (Bacillus cereus, Bacillus firmus and Streptomyces alni) were tested. Extraction with successive selective organic solvents of some plants revealed that the highest residual percentage (31.6%) attained in Artemisia monosperma, while the lowest percentage (17.6%) was found in Euphorbia glomerifera. Ethlyl alcohol was the best solvent for all species. Also preliminary phytochemical investigation of the shoot system of different plants were carried out. From the results, it is clear that Artemisia monosperma contained the highest secondary metabolites, mean while Avena barbata contained the lowest secondary material. We found that the three bacterial antagonistic isolates tested inhibit growth of the pathogenic fungi, with different ratios, but Streptomyces leni was the most effective one. The results indicated that the antibiotics produced by the antagonists were more effective than the bacteria itself and differ with different bacteria. Also the antibiotics produced by Streptomyces were more effective than that of Bacillus. Infiltration of plant stems with antagonist extacts reduce the severity of the disease but not prevent it in all tested pathogens.