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Water productivity of contrasting rice genotypes grown under water-saving conditions in the tropics and investigation of morphological traits for adaptation

Bueno C.S., Bucourt M., Kobayashi N., Inubushi K., Lafarge T.. 2010. Agricultural Water Management, 98 (2) : p. 241-250.

Alternate wetting and drying (AWD) irrigation in lowland rice has been successfully implemented in farmers' fields to reduce water input, and thereby increasing water productivity. Reported effects on grain yield were, however, contradictory: yield was reduced, maintained, or even increased when compared with continuously flooded (CF) conditions. This study was conducted in heavy clay soil to investigate yield variation among a range of genotypes grown underAWDand to determine some aboveground traits related to crop adaptation. The effect ofAWDon grain yield, with a critical threshold of soil water potential for irrigation fixed at ?30 kPa, varied among the 10 genotypes evaluated. Two adapted genotypes were identified with similar grain yield under CF and AWD in both experimental seasons. The grain yield of the aerobic-adapted cultivar included in the study was also maintained under AWD, however, its yield was comparatively low. The reduction in grain yield of the non-adapted genotypes ranged from 9 to 13% in the 2006 dry season and from 6 to 17% in the 2008 dry season. None of the yield components could explain by itself the variability in genotype response: in adapted genotypes, grain yield was maintained because of compensation from or maintenance of yield components, whereas, in non-adapted genotypes, grain yield reduction was not due to the decrease of one component only. Modified biomass partitioning appeared as a main driver for adaptation to AWD: adapted genotypes were characterized by larger sink size at flowering, and weaker stems and less unfilled grain number at maturity, suggesting an increase in the sink strength of the filling spikelets. The aboveground traits identified here will be of great help to further increase water productivity under the AWD strategies set up previously by IRRI water scientists. (Résumé d'auteur)

Mots-clés : oryza

Thématique : Traitement des déchets agricoles

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