Inhibitory effects of rhizospheric and endophytic fungi of Cyperus rotundus on Eleusine indica

BACKGROUND The rhizosphere and root endosphere harbor microbial communities with weed‐suppressive potential. Cyperus rotundus , a highly invasive weed, may leverage such fungi to inhibit neighboring plants. This study aimed to isolate fungal strains from Cyperus rotundus and evaluate their activity against the problematic weed Eleusine indica , with emphasis on mechanisms involving volatile organic compounds ( VOCs ) and hormonal regulation. RESULTS Among fungal isolates from Cyperus rotundus , 120 strains inhibited E. indica germination, and four isolates ( Fusarium oxysporum Wg306, Fusarium andiyazi Fg611, Trichoderma afroharzianum Zg603, and Penicillium raperi Ct105) completely suppressed germination. These fungi markedly affected endogenous hormones in E. indica , most notably a 2934.29% increase in indole‐3‐acetic acid (IAA) under strain Zg603. The other three strains significantly reduced gibberellin acid 3 ( GA 3 ) by 46.16–78.58%, decreased cis ‐zeatin ( cZ) by 33.42–68.33%, and elevated abscisic acid ( ABA) by 6.37–28.43%. Solid‐state fermentation products using agricultural residues (leaves of Cyperus rotundus and sugarcane, rice husks, and rice straw) significantly suppressed E. indica germination, with rice straw showing the strongest effect. Fungal VOCs , including methyl linoleate, β‐elemene, and 3‐octanone, inhibited E. indica shoot and root elongation in vitro , with β ‐ elemene exhibiting the strongest activity (55.31% shoot and 49.64% root inhibition), while causing no inhibition to Oryza sativ a at ≤ 1000 μ M . CONCLUSION This study pioneers four fungal strains from Cyperus rotundus as candidate bioherbicides, suppressing E. indica via VOCs phytotoxicity and hormonal disruption, and finds a novel ecological strategy in which Cyperus rotundus may employ associated fungi to suppress competitors.