The International rice research institute's experience in field screening for drought tolerance and implications for breeding

Lafitte Renée Honor, Courtois Brigitte, Atlin G.N.. 2002. The International rice research institute's experience in field screening for drought tolerance and implications for breeding. . ICRISAT, Rockefeller Foundation. s.l. : s.n., pp. 25-40. International Workshop on Field Screening for Drought Tolerance in Rice, Patancheru, Inde, 11 December 2000/14 December 2000.

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Abstract : There has been considerable investment in trying to understand the physiological basis of genetic variation in tolerance to water deficit in rice. The practical goal of this work has been to develop ways to reliably reveal useful genetic variation in the context of a breeding program. Rice cultivars differ in many traits, such as root depth and morphology, leaf senescence and stomatal conductance under stress, and osmotic adjustment, which are expected to result in different yields under stress. The demonstration of variation among genotypes has been successful, but the link to performance is less clear. Anticipated correlations between traits and performance are confounded by differences in plant type, phenology, and disease and insect resistance, and also by the difficulty of reproducing stress levels across seasons. Managed environments such as dry season nurseries with controlled irrigation can be used to produce fairly repeatable screening experiments. If the objective of the project is to improve grain yield under drought, the stress must be applied at a growth stage that influences grain yield. For rice, this generally means that stress should be applied near flowering. Earlier stress is simpler to apply, but it has not been possible to relate the results of seedling screening to grain yield under stress. The authors have observed that many genotypes perform poorly during the dry season even when the soil water potential is maintained above -20 kPa, indicating that the plants are experiencing mild continuous stress. Yields in these control plots in the dry season tend to be well correlated with yields in stress plots, where water is withheld for 14-20 days around flowering. If yield under these conditions is relevant to performance in farmers' fields in a given target environment, dry season screening can be included in a cultivar improvement program. Results from multilocation testing with climate data are required to make this decision. (Résumé d'auteur)

Mots-clés Agrovoc : Oryza, Résistance à la sécheresse, Amélioration des plantes, Variation génétique, rendement

Mots-clés géographiques Agrovoc : Philippines

Classification Agris : F30 - Plant genetics and breeding

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