ARS | Publication request: PROGRESS IN THE USE OF SMALL-VOLUME AGAR ASSAYS TO DETECT PHYTOTOXIC EXUDATES PRODUCED BY RICE (ORYZA SATIVA L.) ROOTS

Submitted to: Arkansas Experiment Station Research Series
Publication Type: Experiment Station
Publication Acceptance Date: August 1, 2000
Publication Date: N/A

Technical Abstract: Rice roots produced phytotoxic exudates that were capable of diffusing in agar and inhibiting growth of seedlings of the model plant lettuce when it was planted as much as 40 mm away in standard 250 ml agar assays. Rice cultivars differed in their ability to inhibit lettuce growth, presumably because they produced exudates in differing amounts or of differing phytoxic activity. The rice line, 'PI 312777', generally inhibited lettuc more than did the cultivar, 'Rexmont'. Delaying lettuce seed planting for several days after root exudation began caused greater inhibition of lettuce growth, suggesting that sensitivity may be increased with this modification to the assay procedure. Assays using reduced volumes and amounts of root biomass (1/10 or 1/20 that of the standard method) demonstrated that apparent allelopathic activity depended upon the rice cultivar and the mass of rice roots present. Inclusion of known allelochemical standards such as L-DOPA and berberine hydrochloride in aga assays provided a benchmark calibration for apparent allelopathic activity in rice roots. Assays similar to these are being developed to evaluate rice lines against weeds of rice.