Also, the parasitic activity of Streptomyces species upon phytopathogenic fungi was demonstrated by light and scanning electron micrographs (Zamoum Miyada et al. The interaction of Streptomyces with the pathogenic fungi is usually due to the production of cell wall-degrading enzymes such as cellulases, chitinases, amylases, and glucanases. have been widely applied for the biocontrol of plant diseases (Katarzyna et al. Recently, microbial antagonists such as Streptomyces spp. The genus Streptomyces, a unique subgroup of actinomycetes bacteria, is best-known for their ability to produce a variety of weapons as bioactive secondary metabolites, i.e., antibiotics, antifungal, antibacterial, antioxidants, antiparasitic, anticancer, plant growth-promoting substances, insecticidal (Dongli et al. In this context, actinomycetes have been utilized to defend various plants against a wide range of phytopathogenic fungi and bacteria as well as human and insects (Zhao et al. Out of all rhizosphere microbes, actinomycetes are considered as potential biocontrol agents because they exhibit many useful features. Synthetic pesticides are capable to effectively control plant diseases, but some fungicides result in severe environmental and health problems. Due to its unique life cycle, the pathogen infects host plants either through aeciospores that can be discharged reluctantly upwards from apothecia into the air or by mycelium emerging from infected tissue and germinated sclerotia (Zheng et al. sclerotiorum due to the long-term persistence and tolerance of reproductive structures (sclerotia), a wide host range, and unpredictability of infection (Arfaoui et al. Globally, many challenges confront the management strategies of S. Such conditions (cold weather) seemed to be subsidizing factors for white rot infection, thus the growers have been battling large yield losses due to a disease caused by the fungus (Alsum et al. In both dry and green beans, the pathogen causes white mold disease leading to losses ranged from 30 to 100% depending on the favorable conditions (Mohamed and Atallah 2020). In Egypt, bean ( Phaseolus vulgaris L.) plants are grown usually in high moist and cool conditions. It is considered one of the most important limiting factors in producing green beans worldwide (Zheng et al. The white rot (mold) caused by the destructive soil-borne pathogen Sclerotinia sclerotiorum (Lib.) de Bary, affects over 600 plant species including almost all dicotyledonous and some monocotyledonous plants (Shitou et al. sclerotiorum, the causative agent of bean white mold disease.īeans are a staple food source of protein for billions of people worldwide and are suspected of infection by various diseases. The results suggested that the 3 Streptomyces strains and their secondary metabolites can be potential biocontrol agents and biofertilizers for controlling S. in the field proved a great potential to control the disease. Viability and germination of pathogen sclerotia were reduced when they dipped into the Streptomyces spore suspensions for 10, 20, and 30 days. Molecular characterization of the 3 Streptomyces spp. sclerotiorum showed deformation, contraction, and collapse when observed by light and scanning electron microscopy. The parasitic activity of Streptomyces spp. rochei was the highest inhibitor followed by S. The effectiveness of the bioagent volatile compounds inhibited the pathogen growth at a rate of 54.50-72.54%, respectively, revealing that S. sampsonii was more efficient as a bioagent in reducing mycelial growth pathogen by 84.50%. culture filtrate components into culture media proved that S. rochie gave the highest inhibition percent. Reduction percentages in the mycelial growth of the pathogen ranged between 60.17 and 52.30%, indicating that S. The evaluation of bioagents was carried out against S. griseus, and both had a distance relationship with S. The nucleotide sequence analysis of the three Streptomyces spp. PCR amplification of the pathogen and Streptomyces species (bioagents) exhibited amplicons of around 535 bp and 1300 bp, respectively. Molecularly, polymerase chain reaction (PCR) amplification and nucleotide sequencing were used to characterize the pathogen and bio-agents. sampsonii (MN700191 “DG1”) were isolated, biologically, molecularly characterized, and evaluated in vitro and in vivo. The present investigation was carried out to introduce some antagonistic microorganisms as novel antifungal substances to be an alternative and secure method to effectively control the disease. White mold disease, caused by Sclerotinia sclerotiorum the devastating pathogen, attacks green beans ( Phaseolus vulgaris L.) and several crops worldwide.