Characterization of a Phytotoxin from Phoma herbarum for management of Parthenium hysterophorus L.

Microbial products offer a non-chemical alternative to manage noxious weeds with the goal of reducing input into the environment of harmful chemicals that are otherwise used for the same purpose. During the present investigations cell-free culture filtrate (CFCF) of Phoma herbarum FGCC no. 75 was evaluated for its phytotoxic property against Parthenium hysterophorus L. The results of shoot cut, detached leaf and seedling bioassays revealed the presence of a toxic metabolite in the CFCF that was responsible for the toxicity against the target weed. Further, the toxic metabolite was characterized after the CFCF extraction with butanol, hexane, chloroform, acetone and ethyl acetate. The residues left after solvent evaporation were evaluated separately for their toxicity against the weed. Residue obtained from ethyl acetate fraction showed very distinct toxicity when compared with others. On the basis of analysis by gas chromatography- mass spectrometry, the tentative structure of the phytotoxic compound was deduced to be 3-nitro-1,2-benzenedicarboxylic acid (3-nitrophthalic acid). This is the first report confirming the potential of this particular toxin from Ph. herbarum as a biorational, which can be applied as a phytotoxin against Par. hysterophorus.