Direct and correlated responses to divergent selection for leaf abscisic acid concentration in two maize populations

Abscisic acid (ABA) concentration can affect plant responses to drought and has been suggested as a selection criterion to improve drought tolerance. Divergent selection for high (H) and low (L) leaf ABA concentration was con ducted under moderate drought conditions in the F, of maize (Zea mays L.) s ingle crosses Os420 x IABO78 and Mo17 x B88. Objectives of this study were to evaluate direct and correlated responses to the divergent selection. For each cross, the FZ and the H- and L-populations (H-P and L-P) were compare d. For Os420 x IABO78, the comparison was made in one location, for 2 yr, a nd at three irrigation volumes (corresponding to 0, 60, and 120% of crop ev apotranspiration). At all irrigation volumes, H-P exceeded L-P for leaf ABA concentration, drought sensitivity, leaf temperature, silk delay, and lodg ing resistance, while it showed lower plant height and grain yield ton aver age, 3.61 vs. 5.14 Mg ha(-1)). The Fz was intermediate for most traits. Sig nificant differences were not detected for water status traits. For Mo17 x B88, populations were compared at one irrigation volume (60% of evapotransp iration) in three environments. In all environments, H-P was superior to L- P for leaf ABA concentration and drought sensitivity, and it was shorter, a nd less productive ton average, 4.71 vs. 6.95 Mg ha(-1)). The FZ was interm ediate for leaf ABA concentration but not for grain yield. Results indicate that selection for low leaf ABA concentration led to populations with bett er agronomic performance than did selection for high leaf ABA concentration .