Recurrent selection under managed drought stress improves grain yields in tropical maize
1997
Edmeades, G.O. | Banziger, M. | Pandey, S. | Bolanos, J.A. | Chapman, S.C. | Ortega C., A. | Lafitte, H.R. | Fischer, R.A.
After soil fertility, drought is the major abiotic stress limiting maize production in the tropics, and is the most important source of variation in yield over time. Eight cycles of recurrent full-sib (FS) selection or up to four cycles of recurrent S1 selection were practiced on one early-maturing and three late-maturing maize populations adapted to the tropical lowlands. By controlling irrigation in an otherwise dry season, drought stress was applied at flowering and during grain filling. Well-watered nurseries were used to ensure that yield potential was maintained. Selection was for an index of traits that sought to: increase grain yield, reduce anthesis-silking interval (ASI), reduce barrenness, delay senescence, reduce tassel size and increase leaf angle while leaving male flowering date unaltered. Traits related to yield and flowering behavior received the greatest weighting. Gains ranged from 80-108 (mean 94) kg ha-1 yr-1 under FS selection, and from 73-144 (mean 111) kg ha-1 yr-1 under Sl recurrent selection, when selections were evaluated at a yield level of 1.5-2.4 t ha-1 (annual gains 5 Per cent). Under well-watered conditions (5.6-8.0 t ha-1), gains were from 38-108 (mean 73) kg ha-1 yr-1 from FS and from 27-89 (mean 59) kg ha-1 yr-1 from S1 selection. Yield increases were associated strongly with reduced ASI, reduced barrenness and increased harvest index; mildly with delayed leaf senescence and reduced tassel size; and not at all with changes in leaf angle. Biomass production under all conditions and plant water status under drought were unaffected by selection. Reductions in ASI were associated with faster ear growth rates, suggesting an increased partitioning of assimilates to the growing ear. Floret number has declined with selection, but in one population mean floret size at 50 Per cent anthesis doubled.
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