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 beta-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.