Resumen
- The objectives of this work were to identify morphological traits of rice that breeders could use to enhance the ability of this crop to compete with an associated species. Two scenarios were contemplated: a) that of upland rice growing in association with a pasture, and b) that of irrigated rice growing with a weedy species (Echinochloa colona). The first aspect relates to a key component for the sustainable agropastoral systems being developed by CIAT, and the second aspect seeks to reduce the overuse of herbicides in the irrigated rice ecosystem. The experiemnts with the upland rice- pasture associations (two seasons) showed that productive rice plant types can be bred to compete, or tolerate, an intersown pasture such as Brachiaria decumbens. The late onset of competition favored rice over the associated pasture, however, average yield losses for rice growing in competition were 60 and 18% for rice cultivars with the weakest and strongest competitive ability respectively. Competition was strongly related to above-ground light capture, where rice leaf area (recorded after 45 days of emergence) was the key parameter, followed by tillering, while height showed no correlation with competitiveness. Genetic studies for these parameters are being conducted. A similar activity is being conducted in Brazil by EMBRAPA/CNPAF, who are our partners in this ODA-funded prohect.