Three cycles (C0, C4 and C8) of a Tuxpeño maize population selected for eight successive cycles under drought conditions by breeders from CIMMYT were studied to determine if selection changed stomatal conductance (gs) and the capacity to accumulate abscisic acid (ABA).Four week-old greenhouse-grown seedlings were exposed to drought until their relative water contents averaged 60% (at a water potential = -1.7 MPa). ABA was measured by an enzyme immunoassay technique. There were no differences in ABA among selection cycles under drought or under well-watered conditions, indicating that indirect selection for ABA accumulation had not occurred during the breeding procedure and that ABA accumulation was not directly related to increased grain yield under drought. In the same experiment gs was determined using the fourth leaf measured at midday under water-stressed and well-watered conditions. There were no differences in gs among selection cycles under water deficit; however, under non-stress conditions significant differences were found. Seedlings of C8 showed the greatest gs (96.9 mmols m-2 s-1), while C0 and C4 seedlings had lower values (71.2 and 64.6 mmols m-2 s-1, respectively). The reduction in gs with increasing water stress clearly resulted in reduced water loss from transpiration, but was not directly proportional to changes in ABA concentration.

English

9802|AGRIS 9702

Jose Juan Caballero

CIMMYT Publications Collection