Correlated responses to selection for reaction to abscisic acid applied tosilks in maize

Plants grown under drought show an increase of abscisic acid (ABA) concentr ation. whose effects can be mimicked by the application of exogenous ABA. I n a previous study, selection for the reaction to ABA applied to silks befo re pollination was conducted in the maize (Zea mays L.) single cross Mo17 x B88 (MB); silks were sprayed with an ABA solution at 10(-3) M. Objective o f this study was to evaluate the correlated responses for traits of seedlin gs and adult plants grown at different water-stress levels. Non-selected (M B-N) and selected (MB-S) populations were compared in greenhouse water-stre ssed and well-watered conditions. In both conditions. MB-S significantly ex ceeded MB-N for length of primary root and seedling fresh weight, whereas d id not for other seedling traits and for the tolerance index calculated as ratio bem ren water-stressed and well-watered conditions. The two populatio ns were also compared in four field trials with moderate drought from stem elongation to silking. Across trials, MB-S significantly exceeded MB-N for the interval from sowing to pollen shedding (67.9 vs. 67.2 d) and plant hei ght (188 vs. 184 cm), while did not for early vigour, leaf-ABA concentratio n, silk delay, and grain yield. Results indicated that the selection proced ure improved seedling vigour in the greenhouse, whereas did not improve dro ught tolerance under both greenhouse and field conditions.