Herbicidal efficacy of culture filtrates of Alternaria brassicicola and Alternaria gaisen against parthenium weed

Background: Parthenium hysterophorus L. is one of the top ten worst weeds globally and is recorded in the global database of invasive species. Objective: The current study was aimed to evaluate the herbicidal potential culture filtrates against a problematic weed P. hysterophorus. Methods: A. brassicicola and A. gaisen culture filtrates were tested in vitro against the test weed. A. gaisen culture filtrates were found most effective against the test weed, and this test fungus was partitioned with various fractions viz. n-hexane, chloroform, ethyl acetate and n-butanol were isolated. In vitro bioactivity of these fractions were tested against P. hysterophorus. The most productive n-hexane fraction was subjected to GCMS analysis, and thirteen compounds were identified. Results: A. gaisen original (100%) and diluted (50%) culture filtrates showed significant herbicidal activity against P. hysterophorus. However, culture filtrates of A. gaisen suppressed the germination, root and shoot growth of the test weed to a greater extent compared with culture filtrates of A. brassicicola. Original culture filtrates of A. gaisen significantly reduced germination of P. hysterophorus by 88% as compared to diluted concentration by 56% in comparison with control. On the other hand, original and diluted culture filtrates of A. brassicicola reduced the germination of P. hysterophorus by 69% and 50%, respectively, over control treatment. The n-hexane fraction was found more effective in suppressing the P. hysterophorus growth as compared to other fractions. Both 0.10% and 0.05% concentrations of n-hexane fraction significantly inhibited P. hysterophorus seedlings germination by 88% and 81%, respectively. The n-hexane fraction was subjected to GC-MS analysis, and thirteen compounds were identified. Among these, ocimene (27.63%); benzene 1-ethyl-3-methyl-(20.30%) and n-hexadecanoic acid (10.27%) were major compounds. Conclusion: The present study concludes that A. gaisen culture filtrate has substantial herbicidal potential against P. hysterophorous.