Antifungal activity of several medicinal plants extracts against the early blight pathogen (Alternaria solani)

The antifungal activity for several medicinal plants against the early blight fungus (Alternaria solani) has been investigated. These plants were Syrian marjoram (Majorana syriaca), rosemary (Rosmarinus officinalis), Greek sage (Salvia fruticosa), roselle (Hibiscus sabdariffa) and cotton lavender (Santolina chamaecyparissus). The inhibitory effect of these extracts on the radial mycelial growth as well as on spore germination was measured in vitro at various concentrations of crude extract (0.5 g dry plant powder/ml medium). Extracts of M. syriaca and H. sabdariffa were most effective causing total inhibition of mycelial growth and spore germination at 8–10% concentration. Extract of R. officinalis also caused total inhibition of the above two parameters but at double the concentration (20%). Extracts of S. fructicosa and S. chamaecyparissus produced relatively moderate antifungal activity. At 25% concentration, these extracts showed an incomplete inhibition in mycelial growth being around 75–85% and 70–90%, respectively. However, at this same concentration both plant extracts produced total inhibition of spore germination. Results of this study indicated that both extracts of M. syriaca and H. sabdariffa were strong inhibitors of this fungus and to levels comparable to standard fungicides. Further studies are required to determine the effect of these extracts in vivo to evaluate their potential as natural treatments for this disease.