IDENTIFICATION OF RICE CULTIVARS WITH HIGH OSMOTIC ADJUSTMENT CAPACITY FOR THE GENETIC IMPROVEMENT OF DROUGHT TOLERANCE 1

SUMMARY Its genetic dissection, through the identification of quantitative trait loci (QTLs) is an important component of the strategy for the genetic improvement of drought tolerance in local rice cultivars. As a first step within this strategy, we measured the capacity of osmotic adjustment (OA) in 8 local rice varieties (‘Araure 4’, ‘Araure 50’, ‘Cimarron’, ‘Linea 17’, ‘Fonaiap 1’, ‘Fonaiap 2000’ and ‘Venezuela 21’) subjected to water deficit (drought) under glasshouse conditions. The OA values varied between 0.080.6 MPa. ‘Fonaiap 2000’ showed the highest capacity for OA with values ca. 0.5 MPa. In this cultivar, OA was associated with the accumulation of carbohydrates under drought stress. Drought stress symptoms (leaf rolling) appeared later and at more negatives leaf water potemtials (ψh ~ -3.1 MPa) in ‘Fonaiap 2000’ than in the rest of the cultivars studied, indicating that OA is an effective mechanism for maintaining a favorable water status. The values of OA measured in this study are similar to those reported for other cultivars used for mapping QTLs associated to this trait. Thus, ‘Fonaiap 2000’ appears as a good candidate for developing mapping populations for QTL identification and as a potential donor for the improvement of osmotic adjustment capacity in our rice germplasm.