DNA cleavage of the fungal pathogen and production of antifungal compounds are the possible mechanisms of action of biocontrol agent Penicillium italicum against Macrophomina phaseolina .

In the present study, five Penicillium species, namely, P. italicum, P. expansum, P. simplicissimum, P. oxalicum , and P. citrinum , were identified using ITS (internal transcribed spacer) and β-tubulin markers and screened for their in vitro antagonistic potential against a soil-borne fungal pathogen, Macrophomina phaseolina , in a dual-culture plate assay. Among all the tested strains, P. italicum showed the highest antagonistic potential against M. phaseolina by reducing its growth up to 57% over control, followed by P. citrinum (42%), P. simplicissimum (21%), P. expansum (11%), and P. oxalicum (9%). In order to find out the mechanism of action of P. italicum , genomic DNA of M. phaseolina was exposed to P. italicum secondary metabolites. The findings showed that these metabolites completely degraded the fungal DNA after the 48-h incubation period. To further explore the antifungal mechanism of action of P. italicum , chloroform and ethyl acetate fractions of its metabolites were subjected to gas chromatography-mass spectrometry (GC-MS) analysis. The major compounds identified in these fractions were 9,12-octadecadienoic acid ( Z,Z )- (25.19%), decane (19.72%), dodecane (18.05%), benzene, nitro- (14.62%), benzene, 1,3,5-trimethyl (14.37%), benzene, 1,4-diethyl (11.62%), 1,2-benzenedicarboxylic acid, mono(2-ethylhexyl) ester (9.02%), and 1-nonadecene (8.99%), which could be responsible for control of M. phaseolina growth.