Selection for Drought Tolerance Increases Maize Yields across a Range of Nitrogen Levels

Abstract

It is not known whether selection for improved tolerance to a specific abiotic stress leads to correlated changes in performance under other stresses. Drought and N deficiency are important constraints to production in the tropics. We examined the effect of selection for drought tolerance on performance of tropical maize (Zea mays L.) under a range of N levels. Original and advanced selections of four populations, improved for tolerance to midseason drought for two to eight recurrent selection cycles each, were evaluated in two experiments under severe N stress, one experiment under medium N stress, and two well-fertilized experiments. Nitrogen accumulated in the aboveground biomass at maturity averaged 52, 63,105,151, and 163 kg N ha" 1 in the five experiments, and grain yields of 3.0,2.9,5.2,6.0, and 6.5 Mg ha ' were obtained. Selection for tolerance to midseason drought stress increased grain yields by an average of 86 kg ha ' yr" 1 with nonsignificantly larger gains under severe N stress (100 kg ha" 1 yr" 1). Drought-tolerant selections had increased biomass and N accumulation at maturity, the changes being largest under severe N stress. Additionally, drought-tolerant selection cycles were associated with delayed leaf senescence and an increased or unchanged N harvest index, indicating that leaf N was used more efficiently for grain production. Selection for tolerance to midseason drought stress appears to increase grain yield across a range of N stress levels and may lead to morphological and physiological changes that are of particular advantage under N stress. M AIZE YIELDS in farmers' fields in many tropical countries average from 1 to 2 Mg ha" 1 (CIM-MYT, 1994), in stark contrast to yields ranging from 4 to 12 Mg ha" 1 reported on breeding stations in those same countries (e.g., CIMMYT, 1995, 1996). This indicates that farmers in the tropics are growing maize under conditions that differ from those used by many researchers during crop improvement. Abiotic stresses in farm

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Performance of tropical early-maturing maize cultivars in multiple stress environments

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Rainfall and the prediction of sorghum yield in South Africa

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