Breeding for Nitrogen Use Efficiency (NUE) in Maize
Ignacio A. CiampittiPurdue University
Introduction• Nitrogen (N) fertilizer, most important input for
maize production• N uptake and N remobilization is subjected to
genetic variability (in general, >50% of grain originates from the stover)
• NUE, defined as the grain yield per unit of N available from the soil, including N fertilizer
• Two main components, N uptake efficiency (N
uptake/N from soil) and N utilization efficiency (yield/N uptake)
Source of Germplasm or Initial MaterialSource of germplasm or initial
materialLocation Breeding Technique or Method used Results and Conclusions Reference
N-efficient and N-inefficient synthetic cultivars
Tropical region
Genetically broad-based synthetic population composed of various tropical and temperate maize materials and divergently selected among half-sib
families for adaptedness to LN or HN
The selection under LN leads to superior grain yields under LN and selection under HN to superiority
under HN
Muruli and Paulsen, 1981
Landraceaccessions from CIMMYT's
germplasm bankMexico
38 landracesaccessions from CIMMYT's germplasm bank and 26
improved tropical cultivars were compared under adequate and limited levels of soil N
It was concluded that landraces can contribute useful traits for stable
production in N-limitedenvironments, but that selection on
the basis of grain yield alone may be insufficient
Lafitte et al. 1997
European maize landrace core collection (EMLCC)
Spain and Greece
85 landraces EMLCC, grouped in 4 maturity groups, and 3 check hybrids evaluated for LN and HN
Genetic variability is present among European landraces for breeding
progress in NUE traitFerro et al. 2007
Hybrids and open pollinated varieties
EthiopiaHybrids derived from inbred lines and open
pollinated varieties were evaluated in low and adequate N
The better performance of some of this varieties indicate the existence of
genetic variation for NUE traitWorku et al. 2001
Recombined Inbred Lines (RILs) FranceCross between the flint F-2 line and the dent line Io and they crossed the RILs with the inbred line tester
F-252
Greater environmental variances for N uptake trait, related with NUE
Bertin and Gallais, 2000; Coque and
Gallais, 2007
Illinois High Protein (IHP) and Low Protein (ILP), and reverse (IRHP
and IRLP) protein strainsUSA
Inbreds derived from the protein–strains were crossed as males to a common tester and the
resultant hybrids evaluated at eight N rates
They differed in their N use components with IHP and IRLP
exhibiting a higheruptake efficiency, and ILP and IRHP
high utilization efficiency
Uribelarrea et al., 2007
Synthetic cultivar, compared with single and double crosses hybrids
NigeriaBalanced bulks (synthetic) were formed of the
reciprocal crosses
The hybrids were more efficient in N-use and its component traits than the
synthetic cultivar
Akintoye et al., 1999
Low N Pool (LNP) Maize Populations
NigeriaThree cycles of full-sib
recurrent selection
Selection enhanced by selecting for high GY based on N utilization and
on 2nd traits
Omoigui et al., 2007
A set of 213 F2:3 families China
One parent, Huang-C, important Chinese local germplasm – Ludahonggu heterotic group; the other parent, Xu178, exotic germplasm. Nongda 108 is a
high NUE hybrid
The F2:3 population was a NUE
population, and the nutrient component varied widely, suitable for
analyzing the genetic basis of nutrient composition under different N
Liu et al., 2008
Breeding Techniques • Full-sib recurrent selection (e.g. Omoigui et al. 2007)Development of Low N availability pool maize populations under controlled
stress condition, selection using an index (yield, stay green, ASI, etc.)
• Half-sib family method (e.g. Muruli and Paulsen, 1981)Intercrossed with a synthetic population to form a N-efficient and N-inefficient
synthetic (tested under four N supply conditions)
• Hybrid production (e.g. Uribelarrea et al., 2007)Divergent selection for grain protein affects NUE in maize hybrids, crossing
inbreds from IHP and ILP
• Synthetic cultivars (e.g. Uribelarrea et al., 2007)Four inbreds crossed in all directions and synthetic were formed of the
reciprocal crosses (hybrids used as testers)
• Another methods: Mass selection, backcross, reciprocal recurrent selection, etc.
Genetic basis in NUE• Indirect outcome of breeding for higher yields.• The NUE is a highly complex, polygenically
controlled quantitative trait Why?
Moose and Below, 2009
Quantitative trait loci (QTL)• Previous studies have identified QTL controlling
NUE and some of their component traits (Agrama et al. 1999; Bertin and Gallais 2001; Hirel et al. 2001; Gallais and Hirel 2004
• QTLs for N-uptake and N utilization efficiency (at high N input five QTLs explained 39% of phenotypic variance)
• QTLs for leaf nitrate content• QTLs for glutamine synthetase (GS) activity• QTLs for glutamate dehydrogenase (GDH)
• QTLs will have value in combining transgenes with genetic backgrounds that maximize trait expression and stability
(Gallais and Hirel, 2004)
QTLs Location in chromosomes
Candidate Genes for NUE• Genes for which allelic variation could be
responsible for a part of the observed variation• Large number of genes from C and N metabolism
have been mapped (complex network)• Some possible genes associated with NUE: genes
coding for GS, Nr, sh2 (affect starch and protein content),
ADPGppase, Invertase, Sucrose-Phosphate-Synthase (SPS) and Sucrose-Synthetase (SuS), QTLs affecting grain protein and NUE components
Possible function of the GS isoenzymes within the maize plant
(Martin et al., 2006)
RNA Expression Profiling• Another source to identify different candidate
genes• Maize reproductive tissues during grain filling
period• Chiou et al. (2007) reported that only two
miRNAs, miR395 and miR399, have been identified to be important in nutrient stresses responses
• Complexity of the trait, in other experiment 122 genes were upregulated by N and 204 were downregulated by N
Transgenes for improving NUE• Root worm resistance, larger and healthier root system,
possible lead to greater N uptake• Projected release of transgenic maize hybrids with
drought tolerance could indirectly increase the NUE trait• Direct effect, through over expression of GS enzyme,
increased of 30% in maize yield (Martin et al., 2006)• Delayed of senescence, high citokinin levels, “stay
green” phenotype, more photosynthesis extent the N uptake period (affected NUE)
• Future possible transgenes: overexpression NADH-GOGAT (more grain weight) , asparagine synthetase (more N per seed unit), reduced activity of citokinin oxidase (more kernels per ear)
Selection for “secondary traits”
• Correlated trait should have higher heritability (less environmental influence),
• to be easier and economic to measure and
• present a high correlation with the trait of interest.
Geiger, 2009
Breeding in NUE trait• Developing breeding materials excelling in NUE requires field
experiments under strong N-deficiency stress,• Greatest genotypic variance for tolerance to N deficiency is
obtained under severe stress condition resulting to yield reductions of 40–60%.
• Two strategies (i) indirect improvement or (ii) combined selection (selection index)
Moose and Below, 2009
•Breed for increase the Grain Yield Response to N supply•Lowering the amount of N required (Nreq) to obtain a target grain yield without N applied (GY0)•N uptake per plant remained constant over the time, other strategies are required (biotechnology ???)
Response to selection
• Analyzed a second-cycle DH-line population
• Observed a significant linear regression of grain yield under LN on the number of LN-specific yield QTL
• The yield increase per QTL amounted to about 1% on average.
Geiger et al., 2006
• Results, clearly demonstrated that selection under LN leads to superior grain yields under LN and selection under HN to superiority under HN,
• Selection based on an index composed of grain yield and different phenological traits was shown to improve breeding progress considerably.
Conclusions• For increase the sink and the source, the progress understanding
the genetics behind of the physiological pathways.• A large germplasm source and breeding techniques are available for
breeders with a broad range of genetic variability. • A large number of structural genes encoding enzymes of the N and
C metabolism have been mapped to the maize. Easily identified by RNA profiling experiments and other techniques available for improving NUE are the transgenes, gene shuffling and RNAi.
• In terms of transgenes, any transgene improvement on grain yield can impact indirectly on maize NUE trait. The projected release of transgenic maize hybrids with drought tolerance could indirectly increase the NUE trait.
• More research is needed in the genetic bases of NUE, quantitative genetic approach using molecular markers, genomics, and combining both agronomic and physiological studies.
Below, 2002