Herbicidal potential of Alternaria citri Ellis and Pierce metabolites against Parthenium hysterophorus L.
We tested the metabolites of fungal species Alternaria citri Ellis and Pierce for management of invasive weed parthenium (Parthenium hysterophorus L.). Fungal metabolites were prepared in two growth media viz., Malt extract broth (MEB) and Potato dextrose broth (PDB). In laboratory bioassays, metabolites from PDB proved more inhibitory to parthenium germination (92%), shoot biomass (98%) and root biomass (97%) than the metabolites from MEB (43%, 32% and 78% reduction, respectively). Therefore, the metabolites from PDB were selected for pot experiment. In pot culture, 2 concentrations of metabolites, original (X) and concentrated (2X) were sprayed thrice at 4 days intervals on 1-week, 2-week and 3-week old parthenium plants. One-week old plants were highly susceptible to metabolites spray and herbicidal activity of metabolites decreased with increase in age of parthenium plants. There was 66%, 49% and 31% reduction in shoot dry biomass of parthenium due to concentrated metabolites spray on 1-week, 2-week and 3-week old plants, respectively. Fungal metabolites from PDB were fractionated using chloroform and analyzed by GC-MS and 13 compounds were identified. Predominant compounds were hexadecane (20.27%), stearic acid hydrazine (12.9%), phenol, 2,6-bis(1,1-dimethylethyl)- (11.98%) and 10-methylnonadecane (11.05%).