1) Nitrogen use efficiency (NUE) refers to the efficiency with which a plant acquires nitrogen from the soil and utilizes it for growth and grain production. Improving NUE is important to reduce environmental pollution from nitrogen loss and decrease production costs. 2) NUE is a complex trait influenced by both internal genetic factors and external environmental conditions. It has two main components - nitrogen uptake efficiency and nitrogen utilization efficiency. Key physiological and molecular mechanisms controlling NUE include nitrogen transport, assimilation, remobilization and storage. 3) Various approaches can be used to improve NUE in crops, including marker-assisted breeding to introgress quantitative trait loci associated with NUE, transgenic methods to modify expression of genes regulating

1. Shantanu Das
PhD Scholar
Dept. of Plant Breeding and Genetics
Assam Agricultural University, Jorhat-785013
NUE

2. Contents
Introduction.
Need for improvement of NUE
Understanding plant response to N limitation
Physiological basis of NUE
Molecular basis of NUE
Approaches for improving NUE
Case study
Ideotype of Nitrogen use efficient genotype
The relationship between NUE and grain yield
Conclusion

4. What is NUE ?
(Yield obtained per unit of available nitrogen (N) in the soil)
 Physiological NUE =Eefficiency with which the plant
uses N from acquired available N to total plant dry matter
N imported from the field to the crop product
 Agronomic NUE =
N applied.
 NUE is the product of uptake efficiency and utilization
efficiency.
 NUE in plants is a complex phenomenon that depends on
a number of internal and external factors.

5. Where, When and Why NUE traits
are required?
 It’s required in all environmental condition where yield is
required, because NUE crop yield.⍺
 For abiotic stress improvement in crops, NUE has become the
second priority after drought both in the private and in the
public sector.
 To minimize N loss, maximize N uptake & reduce
environmental pollution.
 It’s required in all environmental condition where yield is
required, because NUE crop yield.⍺
 For abiotic stress improvement in crops, NUE has become the
second priority after drought both in the private and in the
public sector.
 To minimize N loss, maximize N uptake & reduce
environmental pollution.

6. Soil
Available N
Key events responsible forKey events responsible for
soil available Nsoil available N

7. Global Status of N fertilizer consumption
& NUE
Global Status of N fertilizer consumption
& NUE
 There is 20-fold increase in the global use of N fertilizer
applications during the past five decades (Glass, 2003) and
this is expected to increase at least threefold by 2050 (Good et
al., 2004).
 The current average NUE in the field is approximately 33%
and substantial proportion of the remaining 67% is lost into
the environment, especially in the intensively cropped area.
 It is estimated that 1% increase in NUE could save $1.1 billion
annually.

8. Need for improvement of NUE
Nitrogen (N) must be supplemented to meet the food production
demands of an ever-increasing population.
The cost of mineral nitrogen fertilizer accounts for a major
portion of the total cost of production.
N recovery by crops is only 30% to 35% of that applied and
remaining 65% to 70% is lost into the environment through a
combination of ammonia volatilization, denitrification, leaching,
immobilization and runoff.
Therefore, Physiologist and plant breeders need to develop
cultivars that can exploit N more efficiently in order to minimize
loss of N, reduce environmental pollution, decrease input cost and
make more economic use of the absorbed N.

9. Understanding plant response to N
limitation
• There may be two type of response to N limitation (i.e.)
1. Adaptive response and
2. Non-adoptive response
Adaptive responses
 Increase in N uptake.
 Retardation of growth and photosynthesis.
 Remobilization of N from older to young leaves and reproductive parts.
 Increased anthocyanin accumulation.
Non -adaptive responses
 Fail to accumulate anthocyanin.
 Having sudden senescence.
 Unable to remobilize N metabolites from rosette leaves towards
developing seeds.

11. Physiological components of NUE
There may be a two components of NUE
1. Nitrogen Uptake Efficiency
2. Nitrogen Utilization Efficiency

12. 1. Nitrogen uptake efficiency
(Amount of absorbed N/quantity of available N)
N uptake efficiency drives biomass production and depend on
Amount of N uptake
Storage
Assimilation

13. N uptake (Kant & Rothstein., 2010)
 For plant N is mainly available in the form of NO3
-
and NH4
+
 There are 3 type of NO3
-
transporter - LATS, cHATS & iHATS
 Km value of cHATS-(about 6-20 μM) [Forde and Clarkson, 1999]
 Km value of iHATS-(about 13-79 μM) [Forde and Clarkson,
1999]
 Several structural gene involve in N uptake
 NRT1 families member (NRT1.1 and NRT1.2) are characterized as
LAT
 NRT2 families member (NRT2.1 and NRT2.2) are characterized as

14. N Assimilation
NO3
-
after entering into the plant cell, assimilation is begin .
N Storage
Absorbed N may stored in the vacoule or directly assimilate
into amino acid

15. Nitrate reductase
No3
-
NO2
-
Nitrate assimilation
Cytoplasm

16. NO2
- Nitrite reductase
NH4
+MoveNO2
-
 Nitrate reductase encoded in nucleus and synthesized in
cytoplasm.

17. Ammonium assimilation

18. 2. Nitrogen Utilization Efficiency
(Efficiency of a plant to utilized N from acquired available N
in the plant for production of biomass)
 Utilization efficiency involved N remobilization.
 At the reproductive stage both N assimilation & N
remobalization become critical.
 Leaves & shoot act as a source for amino acid to the
reproductive and storage organ.
 Upto 80% of the grain N content is derived from leaves in
rice and wheat.
 During leaf senescence N release via protease activities.

19. Amino acid
The predominant gene families which involved in phloem
loading process is AAP (AAP1 - AAP8)
Loading
into
Phloem
NH4
+
Stored Protein

20. Molecular basis of
NUE

21. Genetics of NUE
 NUE is a complex quantitative traits which involves many
genes.
 Expression of multiple gene depend on a number of
internal and external factors.
 There are 100s of nitrate responsive gene.
 For their transcription require regulatory sequence i.e.
NRE (Nitrate responsive element).

22.  One of the such sequence originally reported to be
comprised of an A[G/C]TCA sequence.
 These sequence is randomly distributed throughout the
genome.
 QTL mapping is a powerful tool for analysis of complex
NUE.
 By using QTL mapping in some model spp. such as rice,
arabidopsis and maize, candidate genes encoding enzyme
that involved in N uptake, assimilation and utilization have
been identified.
Contd. (genetics of NUE)

23. Gene involved in Nitrogen uptake
(Kant et al., 2011)

24. Gene involved in Nitrate Assimilation
(Good et. al., 2004)

25. Contd.

27. Agronomic Approach
Optimum N Application_________________
According to phonological stages,
Based on the crop N demand,
Knowledge of plant N uptake efficiency,
Based on soil N status or
Using controlled-release fertilizers - Nitroform®
- Nutralene®
- IB Nitrogen

28.  NUE is affected by
N uptake efficiency - Root characteristics
Physiological N use efficiency (PE)
-mode of photosynthesis i.e. C3 or C4
- N supply
N partitioning b/w leaf & stem
Efficiency of N use in CO2 fixation
Increasing leaf N content
Delay leaf senescence
Higher canopy structure
Physiological Approach

29. Conventional approach
Selection
Backcross method
Molecular approach
Marker assisted selection
Genetic Approach

30. F2
P2
F1
P1 x
ResistantSusceptible

31. Marker assisted backcrossingMarker assisted backcrossing

32. Marker-assisted backcrossing (MAB)
There are three levels of selection in which markers may be
applied in backcross breeding.
 Foreground selection : to screen forthe target trait.
 Recombinant selection: to minimize linkage drag.
 Background selection: to the recovery of the recurrent
parent genome.

33. Transgenic approach
(Abrol, Raghuram & Sachdev, 2007)
GENE GENE SOURCE TARGET PLANT
PHENOTYPE
OBSERVED
Nrt 2.1
Nicotiana
plumbaginifolia
N. tabaccum
Increased nitrate influx
under low N conditions
NR N. plumbaginifolia N. tabaccum
Higher
Nitrate assimilation
NiR Spinacea oleracea Arabidopsis
Higher
Ammonium
accumulation
GS1 Glycine max Lotus corniculatus Accelerated senescence

34. CASE STUDY
Zhang et al., 2015Zhang et al., 2015

35. Identified a major QTL (TOND1) on the long arm of
chromosome 12, confer tolerance to nitrogen deficiency in Teqing
YIL 105 x Teqing
F1
311 F2
34
75
41
Contain TOND 1 Don’t Contain TOND1
150 cultivars (75 Indica and 75 Japonica cultivars) and regions

36. Whether rice cultivars having the TOND 1 allele
exhibit strong tolerance to N deficiency ?
Over-expression of TOND1 increased the tolerance to N
deficiency in the TOND1- deficient rice cultivars.
Identification of TOND 1 provides
a molecular basis of breeding
for breeding rice varieties with
improved grain yield despite input
of N fertilizer
Concluded

37. Ideotype of Nitrogen use efficient genotype
 Increased amount and activity of NR & NiR
 Increased amount and activity of GS & GOGAT
 High root to shoot ratio
 High root vigor & root hair
 High root length density
 N-induced root proliferation
 Microbial symbiosis

38. Grain yield is positively correlated with N uptake
efficiency and N utilization efficiency
Grain yield is positively correlated with N uptake
efficiency and N utilization efficiency

39.  There is a considerable genetic variability for NUE which
provide opportunity for genetic improvement.
 Several candidate gene responsible for NUE have been identify
in several crops like Arabidopsis, Rice and maize etc.
 By hybridization programme, its is enable to transfer
identified NUE related QTL to the genotype having good
agronomic background.
 Incorporation of NUE trait in a genotype will increase
the ultimate grain yield which will contribute to
our national economy.

40. NUE