The role of cultivars in managing weeds in dry-seeded rice production systems

• Weeds are a main biological constraint in the success of dry-seeded rice production.
• There is a need to integrate cultivars with different traits.
• Traits include seed germination in anaerobic conditions.
• High and early seedling vigour with rapid leaf area development at early stage.
• Cultivars having an allelopathic effect and herbicide-resistant rice cultivars.

Dry-seeded rice (DSR) is an emerging production system in Asia. However, weeds are a major biological constraint in the success of DSR production. Although newly available herbicides may provide satisfactory weed control in DSR, an excessive use of herbicides may increase the risk of herbicide resistance and shifts towards problematic weed species. Cultural management practices with the integrated use of cultivars could be exploited to reduce selection pressure and delay herbicide resistance in weeds. The lack of suitable weed-competitive cultivars, however, has been a major constraint in this direction and there is a need to exploit the role of rice cultivars for weed management in DSR. The traits that are likely to be most helpful for weed management in direct seeding include seed germination in anaerobic conditions and tolerance of early submergence for uniform crop establishment, high and early seedling vigour with rapid leaf area development during the early vegetative stage for weed suppression, cultivars having an allelopathic effect, and herbicide-resistant rice cultivars.