A novel screening method for rice allelopathic potential: the inhibitory-circle method

摘要

Screening crop accessions for allelopathic activity is of paramount importance for crop allelopathy research. Previous bioassays often did not use a mixed culture of donor and target plants, did not use soil and were not conducted under natural conditions. In this study, we designed an inhibitory-circle method in which a rice accession (donor plant) and Echinochloa crus-galli (target plant) were cultured together in paddy soil under natural conditions. First, we determined that the highest allelopathic activity of allelopathic rice accession PI312777 was at the 5-leaf stage, and the suitable distance of rice seedlings and E.crus-galli was 12cm apart. This method was then validated by a field test. A further 40 rice accessions were evaluated for allelopathic activity to E.crus-galli using this method. Two rice accessions, PI312777 and Taichung Native 1, had highly allelopathic activity to E.crus-galli (inhibitory rate > 50%), while another accession, Lemont, had non-allelopathic activity. These experimental results were in accordance with previous studies using direct field experiments. The inhibitory-circle method integrated three necessary conditions, that is donor and target plants grown together, with soil as the medium and under natural conditions for reliable results. The inhibitory-circle method', which combined donor and target plants, soil medium and field conditions, can give reliable results in one step, compared with laboratory screening methods. Also, the inhibitory-circle method' gave results in 30-35days, thereby substantially reducing the requirements for time, labour and cost.