To explore the inducible mechanism of weed-suppressive potential in allelopatic rice accession mediated by phosphorus nutrient deficiency, we studied the molecular physiological properties of allelopathic rice regulated by different phosphorus concentrations in hydroponics. We found that in hydroponics, the weed-suppressive potential of allelopathic rice PI312777 was enhanced under low phosphorus treatment, showing higher inhibitory effects on the dry weight of barnyard grass in presence of root exudates of allelopathic rice PI312777 than control (normal nutrient condition). However, reverse was true in non-allelopathic rice Lemont. The expression of four genes encoded the key enzymes involved in phenolic metabolism pathway were all up-regulated in allelopathic rice PI312777, but down-regulated in non-allelopathic rice Lemont, except slightly up-regulated phenylalanine ammonialyase. The HPLC analysis showed that some phenolic acids (Cinnamic acid, caffeic acid, 4-hydroxybenzoic acid, syringic acid and ferulic acid) were enhanced in the leaves, roots and root exudates of allelopathic rice PI312777 under low phosphorus treatment compared to control. But they were not influenced in non-allelopathic rice Lemont. Thus low phosphorus stress increased the allelopathic potential of allelopathic rice PI312777 to prevent the competitor to absorb the nutrients in hydroponics. The enhanced weed-suppressive potential in allelopathic rice mediated by low phosphorus stress was due to the up-regulation of the genes associated with phenolic metabolism, which led to the accumulation of phenolic acids in hydroponic solution from the roots of donor plant.
Allelopathic, gene expression, low phosphorus stress, Oryza sativa L., phenolic acids, rice
