In vitro and In vivo fungicidal activities of toxic cyanobacterium of Neowestiellopsis persica strain A1387 against Alternaria porri

Background: Although cyanobacteria are recognized as renewable sources of biomass for bioactive compounds, they have received little attention as potential biocontrol agents of foliar plant diseases. Purpose : The purpose of this study was to evaluate the fungicidal efficacy of native toxic Iranian cyanobacteria strain Neowestiellopsis persica strain A1387 against Alternaria porri, which causes onion purple blotch disease, in vitro and under greenhouse conditions. Study design: Various concentrations of 1, 5, 10, 15 and 20 mg/ml of cyanobacterial extracellular products of studied cyanobacteria strain were tested for their antifungal activity. Methods: after cultivation cyanobacteria strain, the amount of total cell dry weight, total phenolic compounds and total alkaloid compounds were evaluated. Results: The amount of total biomass, phenolic and Alkaloid compounds was equal to 26.2 ± 0.05 mg/ml, 70.08 ± 0.62 mg/g and 4.24 ± 0.18 mg/g respectively. Identification of compounds using GC-MS showed that Quercetin (28.56147%) and Caffeic acid and Kaempferol (9.275864 and 9.94034%) were the highest and lowest of phenolic compounds respectively, Moreover 1,2-dideuterio-1-deuteriooxy-N-methyl-1-phenylpropan-2-amine; hydrochloride (28.56147%) and Pseudoephedrine (10.67333%) were the highest and lowest of alkaloid compounds. Treatment of infected onion plant with cyanobacterial extract significantly reduced the increase of malondialdehyde and hydrogen peroxide. Also, severity of pathogenicity with Alternaria porri was significantly reduced to 20-50% by applying the 15 and 20 mg/ml of cyanobacteria extract. Conclusion: In conclusion, extracellular metabolites of cyanobacteria extract have potential as effective fungicides to control purple blotch disease of onion.