Allelopathic Potential of Selected Invasive Plants on Early Seedling Growth of Weedy Rice (Oryza spp.)

Weedy rice is a major constraint in rice cultivation, particularly in direct-seeded systems causing significant yield reduction. Current management practices often lack long-term sustainability and environmental safety. Allelopathy has emerged as a potential eco-friendly strategy for the control of weedy rice. This study aimed to evaluate the allelopathic potential of four invasive plant species namely Mimosa pigra, Dicranopteris linearis, Saccharum arundinaceum, and Leucaena leucocephalaagainst the early seedling growth of weedy rice. Dried leaf tissues of the four invasive species were tested using two standard bioassay techniques: dish pack and sandwich methods. Both methods were designed to assess the inhibitory effects of leaf volatiles and water-soluble compounds, respectively. The experiments were conducted under controlled conditions and included multiple weedy rice biotypes. All four invasive species exhibited allelopathic effects, significantly suppressing the shoot and root growth of weedy rice seedlings but limited effect on cultivated rice, MR220CL2. However, the magnitude of inhibition differed among weedy rice biotypes and between bioassay methods suggesting variation in allelochemical potency and modes of action. The tested invasive species possess allelopathic properties that may be explored for developing environmentally sustainable strategies for weedy rice management.