Biosynthesis of Algae based nanoparticles and their potential effect against Charcoal rot disease in common bean (Phaseolus vulgaris L.)

Abstract Macrophomina phaseolina is a soil- and seed borne pathogen causing root rot disease. Disease management using marine macroalgae ( Ulva fasciata ) as well as nanotechnology practices can be a method for disease control. In vitro tests of M. phaseolina control using algal extracts, MgNPs and CH-Mg-alg NC (chitosan- magnesium- algae nanocomposite) as well as CH –alg NC (chitosan- algae nanocomposite) decreases fungal radial growth. We found that these extracts cause distortion in mycelium structure. HPLC analysis of the algal extract showed the presence of eight major phenolic compounds that may have an antifungal activity. The CH-Mg-alg NC treatment had the largest inhibitory effect decreasing radial growth by 88.9% compared to the control. The hydrodynamic diameter of the CH-Mg-alg NC particles includes two picks at 7.36 nm and 898.9 nm with a polydispersity index (PDI) of 0.34 and a zeta potential of -11.0 mV. In pot experiments, disease severity decreased after the CH-Mg-alg NC seed soaking treatment with a severity reduction of 56.43 to 23.81 and 53.53 to 25.02% in the first and second season, respectively. The treatments also improved vegetative growth parameters compared to the positive untreated control. To track the distribution of the nanocomposite within the pods and soil, data obtained from Inductively Coupled Plasma (ICP) spectrometry indicated that the magnesium (Mg) ratio not increases beyond the natural/safe levels in both the pods and soil. These findings support the safety of the application of CH-Mg-alg NC in disease management strategies.