Relationships among weed suppression effect, allelopathy and agronomic characteristics of Oryza longistaminata and related descendants

Rice allelopathy has been a new environmentally-safe way in paddy weed management that has met the needs of sustainable agriculture. This study explored the linkages among field weed suppression effects, allelopathy and agronomic characteristics of Oryza longistaminata and its related descendants. It critically exploited and utilized the important aspect of allelopathic genes of wild resources of rice germplasm. In the paper, wild rice (O. longistaminata) with allelopathic potential and 'RD23' (O. sativa cultivar) without allelopathic potential and their F1 (RD23 × O. longistaminata) and F2 descendants were used in indoor assay and pot cultivation experiment in greenhouse to determine the effect of allelopathy and agronomic characters on weed suppression effects to barnyard grass. The results showed that weed suppression effects of strong allelopathic potential rice were significantly higher than those of rice with weak allelopathic and non-allelopathic potential at a rhizosphere distance of 0?3 cm under pot culture conditions. However, strong allelopathic potential rice not always had higher weed inhibition effects with increasing rhizosphere distance. When rhizosphere distance was greater than 3 cm, rice with strong tillering ability, fast growth and long upright stems had stronger weed inhibition effects under pot culture conditions irrespective of the allelopathic potential of the tested rice materials. Density control effect of rice seedlings aged 60 days was lower than those aged 30 days at rhizosphere distance of 0?3 cm. However, biomass control effect and plant height inhibition rate were greater for seedlings aged 60 days. With increase of rhizosphere distance, not significant difference was noted between seedling with two ages, except density control effect at rhizoshpere distance of 3?6 cm. Correlation analysis of allelopathy synthesis effects with density control effect, biomass control effect and plant height inhibition rate depicted weakening correlation with increasing rhizosphere distance of the tested rice materials, but with significant correlation at 0?3 cm rhizosphere distance. Although no correlation was noted between plant height, tiller number and density control effect, but biomass control effect and plant height inhibition rate was positively correlated with plant height and tiller number of the tested rice materials. The study suggested that field weed suppression effect of O. longistaminata and its F1 (RD23 × O. longistaminata) and F2 accessions depended on allelopathy, seedling age, plant height, tiller number and other factors of the rice field. Allelopathy was an important factor at 0-3 cm rhizosphere distance and 30 days of rice seeding age.