eng Enviro Research Publishers Current Agriculture Research Journal 2347-4688 2321-9971 2025-04-30 13 1 230 242 24142 article Kamini Yadav 1 Sushila Arya 1 Sandhya Kumari 1 Pratiksha Khadka 1 Department of Agriculture, Dev Bhoomi Uttarakhand University, Dehradun, Uttarakhand, India Parthenium hysterophorus L., commonly known as carrot grass (Gajar ghaas), is an annual plant in the Asteraceae family. This study aimed to examine the biological activity and chemical makeup of essential oils extracted from P. hysterophorus plants collected from Dehradun and Haridwar district, Garhwal region, Uttarakhand, India. The plant material underwent hydro-distillation using a Clevenger apparatus to extract the volatile oils. These essential oils were then analyzed for their chemical constituents using Gas Chromatography-Mass Spectrometry (GC-MS). The GC-MS analysis identified several major compounds in the essential oils from both districts, including β-cyperone (5.11-12.16%), 1-isopropenyl-4-methyl-1,2-cyclohexanediol (3.0-3.7%), 2,3-bornanediol (1.73-6.13%), isolongifolol (1.32-2.73%), saussurea lactone (0.76-7.81%), and neoclovene oxide (0.97-1.48%). Using Principal Component Analysis (PCA) and heat map clustering, the differences in biological activity and chemical composition of the oils were visualised. These analyses helped illustrate the differences and similarities in the chemical profiles and biological effects of the oils from the two districts. Both essential oils demonstrated significant allelopathic effects against Raphanus raphanistrum subsp. sativus (wild radish) seeds and showed moderate antifungal activity against Colletotrichum lindemuthianum and Curvularia lunata. These findings indicate that the essential oils from Parthenium hysterophorus L. possess notable allelopathic and antifungal properties, suggesting their potential applications in agriculture. https://www.agriculturejournal.org/volume13number1/comparative-chemical-composition-and-biological-activity-of-parthenium-hysterophorus-l-essential-oil-from-two-sites-in-garhwal-region-uttarakhand-india/ Allelopathic; Antifungal activity; Colletotrichum lindemuthianum; Curvularia lunata; Essential oil; Parthenium hysterophorus