الفهرس 
Use of some streptomyces species as bio-agents to control bean white rot disease caused by sclerotinia sclerotiorum
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Abstract
White mold disease, caused by Sclerotinia sclerotiorum the devastating pathogen, attacks green bean (Phaseolus vulgaris L.) and several crops worldwide. The present investigation was conducted to introduce some antagonistic microorganisms as novel antifungal substances to be an alternative and secure method to effectively control the disease. Out of 24 isolates,three Streptomycesisolateswere molecularly characterized.PCR amplification of the fungus pathogen and Streptomycesisolates 16S rDNA gene sequences exhibited amplicons of around 535bp and 1300bp, respectively. Thecharacterized Streptomycesisolates were sequencedand submitted into Genebank under accession numbers i.e., S. griseus (MT210913 ”DG5”), S. rochei (MN700192 ”DG4”) and S. sampsonii (MN700191 ”DG1”). Phylogenetic tree of the nucleotide sequence analysis of the three Streptomyces spp. indicatedthat S. griseus MT210913 was closely related to S. sampsonii MN700191 (96%), secondly ranked by S.rochei MN700192 (93.1%).Afterward, the antifungal activityof Streptomyces spp. against S. sclerotiorumwas evaluated in vitro and in vivo(in the greenhouse and field).In vitrotests,proved that the reduction percentages in mycelial growth of pathogen ranged between 31.4-60.17%, indicating that S. rochie gave the highest inhibition percent. Incorporations of Streptomyces spp culture filtrate components into culture media provedthat S. sampsonii was more efficient as a bioagent in reducing mycelial growth pathogen by 84.50%. When the effectiveness of the bioagent volatile compounds was evaluated, the inhibition of the pathogen growth ranged between 54.50-72.54%, respectively, revealing that S. rocheiwas the highest inhibitor followed byS. griseus.Results of GC-Mass analysis revealed the presence of 44, 54 and 47 diverse secondary metabolites compounds produced by S. sampsonii DG1, S. rochie DG4, and S. griseus DG5, respectively.Examining parasitic activity of Streptomyces spp upon S.sclerotiorum was demonstrated by light and scanning electron (SEM) micrographs exhibited the interaction as deformation, contraction, and collapse in the mycelium of the pathogen