Improving Nitrogen-Use Efficiency in European Maize : Estimation of Quantitative Genetic Parameters

Agricultural Organization of the United Nations, 2000). Apart from factors such as crop rotation and type of N Maize (Zea mays L.) cultivars with improved N-use efficiency would be beneficial for low-input production systems. Our objective fertilizer and its application, crop cultivars with imwas to estimate quantitative genetic parameters to optimize breeding proved N-use efficiency have much to contribute to programs for improving productivity under low N levels. Results of production systems where input of N fertilizers is re21 field experiments with European breeding materials belonging to stricted due to environmental and/or economical the flint and dent gene pool are presented. The study was performed reasons. during 1989 and 1999 at several locations in typical maize growing N-use efficiency is defined as the ability of a genotype regions of Germany and France. All experiments were conducted at to produce superior grain yields under low soil N condihigh (HN) and low (LN, no N fertilizer applied) N levels. Average grain yield was reduced by 37% at LN compared with HN. Coefficients tions in comparison with other genotypes (Graham, of genotypic correlation between HN and LN were variable with an 1984; Sattelmacher et al., 1994). Experiments with the average of rG 0.74 for grain yield and generally high for grain dry U.S. Corn-Belt (Balko and Russell, 1980), tropical matter content. For grain yield, analyses of variance were computed (Muruli and Paulsen, 1981; Lafitte and Edmeades, 1994; from relative data, where plot values were expressed as percentage Bänziger et al., 1997), and European maize (Bertin and of the trial mean. Variances caused by genotype (G), G location Gallais, 2000) indicated that genotypes can differ con(L) interaction, and error effects were higher at LN compared with siderably in their N-use efficiency. Hence, breeding for HN, with similar heritabilities at both N levels. For the untransformed data, components of variance were higher at HN than at LN. adaptation to low soil N seems feasible. Genotype N as well as G L N level interaction variances were It would be desirable to combine the breeding goals significant in most experiments. Efficiency of improvement of grain of yield improvement for conditions with high input of yield at LN through indirect selection at HN was 70% compared with N fertilizers and yield improvement for low N input direct selection at LN. A trend toward increased efficiency of direct conditions. In principle, the following two breeding selection under LN conditions was evident with decreasing grain yield strategies are possible (Atlin et al., 2000; Falconer, at LN. 1952): (i) Indirect improvement: selection at only one N level, whereby performance at the other N level is improved by correlated response; (ii) Combined imF 1960 to 1990, the use of N fertilizer in modern provement: selection is based on an index of the agricultural systems has increased in parts of Asia, weighted performance means at high and low input of North America, and West Europe (Food and Agricultural Organization of the United Nations, 2000). This N. If combination of the two breeding goals proves to was accompanied by a steady growth in average maize be ineffective, it would be necessary to breed for the yield during the same period. On the other hand, negaHN and LN environments separately. To decide which tive impacts of N-compounds on the atmosphere, the of the strategies would be the most appropriate, knowground water, and other components of the ecosystems ledge of quantitative genetic parameters such as genohave also been reported (Socolow, 1999). Because of typic variance components, heritabilities, coefficients of these negative effects, the European Community develgenotypic correlation, as well as economic weights for oped specific directives (Nitrates directive 91/676/EEC) yield under high and low N conditions is necessary. So to prevent nitrate contamination of water from agriculfar, quantitative genetic parameters for the adaptation tural sources, such as by restricting the use of N fertiliof European maize to low soil N conditions were only zers, enlarging the water protected areas, as well as provided by Bertin and Gallais (2000). The authors stuincreasing the acreage of organic farming (Organic Cendied the testcross performance of 99 recombinant inbred tre Wales, 2001). In many tropical and subtropical relines at two N levels. However, comprehensive studies gions, and in countries of the former Soviet Union, on the N-use efficiency of maize using different sets of farmers cannot increase yield, as the availability of N materials across a wide range of environments are only fertilizers in crop production is often limited (Food and available for tropical maize (Bänziger et al., 1997). T. Presterl and H.H. Geiger, Inst. of Plant Breeding, Seed Sci., and Our study summarizes results of 21 experiments with Population Genetics, and E.M. Thiemt, State Plant Breeding Institute, European maize breeding materials. The objectives Univ. of Hohenheim, D-70593 Stuttgart, Germany; G. Seitz, AgReliwere (i) to evaluate differences in N-use efficiency of ant Genetics, Westfield, IN 46074, USA; M. Landbeck and W. the genotypes and (ii) to estimate quantitative genetic Schmidt, KWS SAAT AG, 37555 Einbeck, Germany. Funding for this study was provided by the Ministry of Agriculture of Badenparameters to design and optimize breeding programs Württemberg (Grant No. 89.23-20, No. 23-92.9, and No. 23-95.8) and for cultivars with improved N-use efficiency. the KWS SAAT AG, Einbeck. Received 8 Nov. 2001. *Corresponding author (presterl@uni-hohenheim.de). Abbreviations: HN, High N level; LN, Low N level. Published in Crop Sci. 43:1259–1265 (2003).