Physiological and yield responses of contrasting upland rice genotypes towards induced drought.

Drought alters rice morphophysiology and reduces grain yield. This study hypothesized that the combined analysis of morphophysiological and agronomic traits enables a systemic approach to responses to water deficit, allowing the selection of resistance markers to upland rice. The objectives were to evaluate the effects of water deficit applied at the reproductive stage in plant water status, leaf gas exchanges, leaf non-structural carbohydrate contents, and agronomic traits in upland rice genotypes; and to verify if the analyzed variables may be applied to group the genotypes according to their tolerance level. Water deficit was induced by irrigation suppression in eight genotypes at R2-R3. Physiological and biochemical traits were evaluated at the end of the water deficit period, thenceforth irrigation was restored until grain maturation for the analysis of the agronomic traits. Water deficit reduced: Ψ_w (63.64%, average); g_s (28–90%); transpiration rate (40.63–65.45%); RWC from Serra Dourada to Esmeralda (43.36–61.48%); net CO₂ assimilation from Serra Dourada to Primavera (70.04–99.91%); _iWUE from Esmeralda to Primavera (83.98–99.85%); _iCE in Esmeralda (99.92%); 100-grain weight in CIRAD and Soberana (13.65–20.63%); and grain yield from Primavera to IAC 164 (34.60–78.85%). Water deficit increased C_i from Cambará to Early mutant (79.64–215.23%), and did not affect the tiller number, shoot dry biomass, fructose, and sucrose contents. The alterations in the variables distinguished groups according to the water regime. RWC, Ψ_w, leaf gas exchanges, and _iCE were valuable traits to distinguish the water regime treatments, but not to group the genotypes according to the drought tolerance level. [ABSTRACT FROM AUTHOR]