Allelopathic potential of Chinese medicinal plants on rice and paddy weeds

Allelopathic potential of 10 Chinese medicinal plants were investigated on rice and 3 paddy weeds. All medicinal plants inhibited the germination and growth of both rice and paddy weeds but the inhibitory effects were much stronger on paddy weeds than on rice. Medicinal plant species: Punica granatum, Setaria viridis, Aconitum carmichaeli and Ricinus communis were most inhibitory to paddy weeds. Particularly, P. granatum completely inhibited the germination and growth of 3 test paddy weeds (Echinochiloa crusgalli, Pycreu sanguinolentus and Bidens tripartite). Furthermore, its methanol extract was partitioned into three fractions: n-butyl alcohol, ethyl acetate and water and their allelopathic activities were evaluated on the growth of rice and 3 paddy weeds in bioassay. The weed-suppression of three fractions followed the order: n-butyl alcohol > ethyl acetate > water. At 5g/L dose, n-butyl alcohol fraction caused 90% inhibition in growth of 3 paddy weeds, but no inhibition was observed in rice. GC/MS analysis showed that ergost-5-en-3ol, (3β,24R)-stigmast-5-en-3-ol, (3β,24S)- 9,19-cyclo-9β-lanost-24-en-3 β-ol and n-hentriacontane were the main compounds of bioactive nbutyl alcohol fraction of P. granatum. This study suggested that several Chinese medicinal plant species, such as P. granatum, could be used for management of paddy weeds.