Efficacy of Althaea officinalis leaf extract in controlling Alternaria spp. pathogenic on Citrus
2021
Maghsoodi, Fatemeh | Taheri, Parissa
In this study, inhibitory effects of the aqueous and ethanolic leaf extracts obtained from marshmallow (A. officinalis) were evaluated against Alternaria spp., pathogenic on Citrus. The marshmallow leaf extracts were added to potato dextrose agar medium at various concentrations and antifungal effect of the extracts against three species of Alternaria pathogenic on citrus was tested in vitro and in vivo. The ethanolic leaf extract revealed significant inhibitory effect on the mycelial growth of all fungal species and complete inhibition on spore germination of the pathogens at 100 mg mL⁻¹ concentration, similar to those of the fungicide tested. Microscopic analysis revealed that the extract caused morphological changes, including abnormal hyphal morphology with a rough surface and shriveled hyphae. The HPLC analysis revealed the presence of phenolic/flavonoid compounds, including chlorogenic acid, quercetin, benzoic acid, apegenin, cinnamic acid, ferulic acid and Kaempferol. Results of enzyme activity assays revealed that the activity of cellulase, amylase, protease and pectinase reduced in the samples treated with the ethanolic extract. The ethanolic leaf extract protected Citrus sinensis (orange) fruits against the pathogens and reduced lesion diameter of Alternaria disease in a concentration dependent manner. The concentrations of 50 and 100 mg mL⁻¹ were the most effective in reducing lesion diameters on citrus fruits campared to the control. Both in vitro and in vivo assays revealed potential of marshmallow ethanolic leaf extract to be used as a safe and eco-friendly protectant of citrus fruits against Alternaria spp. as destructive pre- and post-harvest fungal parhogens. Future research seems to be necessary to investigate antifungal effect of the major components detected in marshmallow leaf extract and determine the best formulation to increase its efficiency against phytopathogens.
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