Abstract
Rose rust caused by Phragmediumsp is one of the most important diseases adversely affecting its yield in Saudia Arabia. In this study, Identity of the causal agent fungus was confirmed by LSU rDNA sequencing and identified as Phragmidiummucronatum. Also, the present study is focused on the extracellular synthesis of silver nanoparticles (AgNPs) using culture supernatant of an agriculturally important bacterium, Proteus maribials and demonstrates its effective application for the management of rust disease in rose. The biosynthesis of AgNPs by Proteus maribials was monitored by UV-visible spectrum that showed the surface plasmon resonance (SPR) peak at 406 nm, an important characteristic of AgNPs. Further characterization of synthesized AgNPs carried out using the X-ray diffraction (XRD), transmission electron microscope (TM) and FTIR spectroscopy, respectively. The AgNPs were spherical in shape with size range of similar to 10 to 20 nm. The XRD analysis confirmed successful biosynthesis and crystalline nature of AgNPs. The AgNPs exhibited strong antifungal activity against P. mucro, the rust disease pathogen of rose. Interestingly, all concentrations of AgNPs (0.25, o.5 and 1 mM) used displayed a strong inhibition of urediospore germination, 3.05, 2.2, and 1.1% respectively, whereas in the absence of AgNPs, urediospore germination was 62.32 %. The results were further tested under field conditions, where application of AgNPs significantly reduced P.mucronatuminfection in rose plants. The averages of disease severity were reduced from 3.6 in non-sprayed plants to 1.06 % in case of spraying with AgNPs (1mM). In summary, our findings represent the efficient application of AgNPs in rust disease management, therefore, it is recommended to consider biological synthesized silver nanoparticles in further studies for possible controlling of rose rust diseas