Plant diseases cause lots of losses worldwide, and pathogens identification is essential during diseases studies. Traditional identification of phytopathogens mainly relied on host information and pathogen morphological characteristics, which limited the discovery of similar pathogens on the same hosts. Recently, the application of phylogenetics to plant pathology greatly promotes the discovery of larvaceous fungi. For example, novel genera in Cryphonectriaceae were described as phytopathogens continuously in the past two decades. Cryphonectriaceae is a worldwide fungal family, with most members pathogenic to Myrtiflorae and Fagaceae plants. This family was established in 2006, basing on EndothiaCryphonetria complex, Amphilogia, Chrysoporthe and Rostraureum (Gryzenhout et al., 2006). Further studies increased 17 genera in this family depended on DNA sequence data, supported by morphological evidence.

Members of Diaporthe are known as plant pathogens, endophytes or saprobes on a wide range of host plants. Diaporthe species are wellknown as the causal agents of many important plant diseases; including root and fruit rots, dieback, stem cankers, leaf spots, leaf and pod blights, and seed decay (Udayanga et al., 2011). Diaporthe helianthi is the causal agent of one of the most important diseases of sunflower (Helianthus annuus) worldwide, and is also listed in the Chinese quarantine directory (Thompson et al., 2011). For plant pathologists, studying of phytopathogenic Diaporthe spp. is therefore particularly important to work on wide range of plant diseases (e.g. grapes, sunflowers, soybean, and various diseases associated with ornamentals and forest trees). The taxonomy of Diaporthe spp. has recently been reviewed in several impactful studies (Udayanga et al., 2011; Gomes et al., 2013).

Development of biologically inspired experimental processes for the biosynthesis of nanoparticles (NPs) is an evolving important branch of nanotechnology. In the present work, we studied the potential of four bacterial species for extracellular production of nanosilver (AgNPs) from 3 mM concentration of silver nitrate (AgNO3) after incubation for 4h at 85°C. Biosynthesized AgNPs were characterized by using different methods such as; UV/vis spectroscopy, Transmission electron microscope (TEM), X-Ray Diffraction (XRD) and Fourier Transform Infra-red (FTIR) spectroscopy. Results of UV–vis spectroscopy showed maximum absorption at 401-432 nm, which represents the characteristic surface plasmon resonance of AgNPs. TEM demonstrated that the size range of these NPs ranged approximately from 7.8- 13.4 nm. Representing the XRD pattern obtained for the AgNPs, a number of Fcc structures of silver Bragg reflections corresponding to (100), (110), (111), (200) and (220) planes were observed. FTIR results recorded a downward shift of absorption bands between 400–4000 cm-1 indicating the formation of AgNPs. Finally we concluded that the extracellular biosynthesis of AgNPs by the four bacterial species; Ochrobactrum sp. (MAM-C9), Achromobacter xylosoxidans (MAM-29), Pseusomonas aeruginosa (MAM-42) and Bacillus cereus (MAM-I.11) were confirmed. This study recorded that bacterial biosynthesis of AgNPs is useful to avoid adverse effects of chemical and physical methods that are non-suitable for medical applications.