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Terry Rose, Southern Cross Plant Science/Southern Cross GeoScience

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Enhancing internal phosphorus use efficiency in crops: concepts and approaches Terry Rose, Southern Cross Plant Science/Southern Cross GeoScience – PowerPoint PPT presentation

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Title: Terry Rose, Southern Cross Plant Science/Southern Cross GeoScience


1
Enhancing internal phosphorus use efficiency in
crops concepts and approaches
Terry Rose, Southern Cross Plant
Science/Southern Cross GeoScience
2
Internal phosphorus use efficiency
  • Three main ways we examine it
  • Molecular and physiological responses from P
    starved model plants (e.g. arabidopsis)
  • Investigate mechanisms in highly P-efficient
    non-crop species
  • Investigate and attempt to exploit genetic
    variation within a crop species

3
Definitions of Internal Phosphorus Use
Efficiency
  • Grain yield per unit of P in above-ground tissue
    (g mg-1)
  • - yield formation may be independent of P
    use
  • - selects against genotypes with low grain
    yield potential
  • Biomass yield per unit of P in above-ground
    tissue (g mg-1)
  • - inverse of tissue P concentration
  • Critical shoot P concentration for 90 maximum
    yield (mg g-1)
  • - expensive when screening large numbers
  • Shoot biomass/shoot P concentration (g2 mg-1)

www.scu.edu.au/scps/
4
Problem caused by differential P uptake
29 rice genotypes grown in low P soil for 50 d
with four replicates
www.scu.edu.au/scps/
5
Can screening at equal P uptake help?
  low-P soil low-P soil 500 µg P hydroponic 500 µg P hydroponic P hydroponic P hydroponic
  Total P Total DM Total P Total DM Total P Total DM
ShtPUE -0.81 -0.65 -0.43 0.51 -0.30 -0.02
SeedP 0.10 0.07 0.40 0.59 0.10 0.10
www.scu.edu.au/scps/
6
Screening large numbers in hydroponics
  • GWAS study needed P controls for two reasons
  • Can remove any genotypes that grew poorly in P
    from any analyses poor growth at low-P not
    related to low P but other artefacts
  • Can map GWAS peaks under P conditions to find
    loci related to general vigour and not
    specifically related to P

www.scu.edu.au/scps/
7
Genome-wide association study (GWAS) for PUE
Main QTL on chromosomes 1 (indica) and 11 (aus)
www.scu.edu.au/scps/
8
Does internal PUE ranking change with shoot P
content?
There is no presumption that high internal PUE
lines will grow well in the field because they
may lack P uptake genes The aim is to find
loci/gene(s) that can be pyramided into elite
lines in local breeding programs.
www.scu.edu.au/scps/
9
What are the consequences of higher internal
PUE ?
These authors apply The law of conservation of
matter to nutrient use efficiency.
www.scu.edu.au/scps/
10
What are the consequences of higher internal
PUE ?
Source Rose et al. 2013 Frontiers in Plant
Science
www.scu.edu.au/scps/
11
What are the consequences of higher internal
PUE ?
  • Obtained same biomass as the wild-type plants
    with a quarter of the P content in shoots, while
    seed yield was not reduced.
  • No seed P concentrations shown

www.scu.edu.au/scps/
12
What are the consequences of lower seed P
concentrations?
  • Grain quality milling traits in rice, dough
    quality in wheat?
  • Human health
  • 1. P deficiency in humans? Unlikely.
  • 2. phytate
  • - Some reports suggest it may have
    anti-cancer properties, recent review
  • by Kumar et al. (2010) suggests that
    there is limited evidence for this
  • - Strong evidence for its role in binding
    micronutrients, so reduction in
  • phytate may be beneficial
  • 3. phospholipids
  • - play a role in grain quality and human
    health, but may be quite stable
  • (Tong et al. 2014)

www.scu.edu.au/scps/
13
What are the consequences of lower seed P
concentrations?
  • Seedling germination and vigour
  • Two lines of enquiry have led to the conclusion
    that reducing seed P is detrimental to seed
    germination and vigour.
  • Studies with low phytic acid (lpa) mutants
  • - Low-phytic-acid mutants often have
    impaired germination and vigour
  • BUT this is because whole genes are often
    knocked out
  • - The only LPA mutant used in breeding
    programs (Barley lpa1-1 Bregitzer et al.
  • 2007 Crop Science) has no impact on
    seedling vigour BUT this mutant has a
  • 10-14 reduction in seed total P due to
    mutation of a putative sulfate
  • transporter.

www.scu.edu.au/scps/
14
Seed germination and seedling vigour
  • 2. Studies with low-P seed from P-starved plants
  • Half a dozen studies with cereal crops where
    low-P seed have shown reduced germination and
    seedling vigour compared to high-P seed
  • These studies do NOT make fair comparisons
    because the low-P seed came from P-stressed
    parent plants
  • Most studies were not conducted with agricultural
    soils with a history of P fertilisation, so soils
    were typically highly P-deficient.

www.scu.edu.au/scps/
15
Seed germination and seedling vigour
  • 2. Studies with low-P seed from P-starved plants
  • Seeds from P-starved plants performed poorly in
    P-deficient soil but no yield difference in
    agricultural soil supplied with P fertiliser
  • Subsequent studies with seed lower in P from
    environmental effects found no difference in
    seedling vigour between high- and low-P seed on
    any soil
  • Further studies have been conducted and will be
    the focus of the presentation by
  • Elke Vandamme

www.scu.edu.au/scps/
16
High P input farming systems
  • If seedling vigour can be maintained with lower
    seed P, then perhaps we could breed for lower
    seed P concentrations regardless of internal PUE
    at the vegetative stage. Go for high P uptake and
    low translocation to grains.
  • May be a useful trait in high-input farming
    systems where the removal of P in grains is
    significant and drives the need for continual P
    fertiliser input

World phosphate deposits FAO data Australian
deposits are lt 1 of world P resources. Over
70 of resources are held by China and Morocco.
www.scu.edu.au/scps/
17
High P input farming systems
www.scu.edu.au/scps/
18
High P input farming systems
www.scu.edu.au/scps/
19
High P input farming systems
www.scu.edu.au/scps/
20
High P input farming systems
www.scu.edu.au/scps/
21
High P input farming systems
  • In an average season in Australia, approximately
    60, 000 tonnes of P (the equivalent of over half
    a million tonnes of super phosphate) is removed
    off-farm in wheat grain at harvest assuming grain
    contains 3 mg P/g.
  • Most is exported overseas while some is consumed
    domestically and contributes to high-P landfill
    and the pollution of water bodies in Australia.
  • A reduction in grain P concentrations to 2 mg P/g
    would save about 100 million being removed off
    farm each year at 5 per kg P.

www.scu.edu.au/scps/
22
  • Current research project
  • Global Rice Science Partnership (SCU, JIRCAS,
    IRRI, AfricaRice) project aims to reduce rice
    grain P by minimum 20
  • Approaches for breeding crops with low grain
    phosphorus
  • Two approaches investigated in the project
  • Exploiting genotypic variation
  • Molecular approach
  • Mutant approach not investigated but may be an
    option later

www.scu.edu.au/scps/
23

GRiSP project Exploiting genotypic
variation Multi-location trials with 20 rice
genotypes over a number of years to look at G x E
interactions for grain P concentration 1. Need
to identify a genetic component that is
independent of grain yield (yield-dilution
effect) 2. Need to make sure low grain P isnt
associated with low plant P uptake! Elke
Vandamme will be presenting data on this
www.scu.edu.au/scps/
24

GRiSP project Molecular approach Identify P
transporter(s) and use RNAi silencing to reduce
gene expression in specific tissue at a specific
time Understand regulatory pathway of genes
involved in grain P loading and find targets for
genetic manipulation
www.scu.edu.au/scps/
25
  • Summary
  • We have investigated internal PUE at the
    vegetative stage using a method which screens at
    equal P uptake and have mapped loci for high
    internal PUE
  • The consequences of high internal PUE will likely
    be a reduction in grain P concentration
  • Reducing grain P concentration may be a good
    option by itself, particularly in high-input
    systems
  • Further work is needed to ensure lower grain P
    concentration does not adversely affect grain
    quality or seedling vigour

www.scu.edu.au/scps/
26
  • Acknowledgements
  • Southern Cross University
  • Cecile Julia
  • Kwanho Jeong
  • Alicia Hidden
  • Rachel Wood
  • Japan International Research Centre for
    Agricultural Science
  • Matthias Wissuwa
  • Asako Mori
  • Juan Pariasca-Tanaka
  • Katsuhiko Kondo
  • Africa Rice
  • Elke Vandamme
  • Kazuki Saito
  • IRRI
  • Tobias Kretschmar
  • Funding Agencies
  • Global Rice Science Partnership
  • Japan Society for the Promotion of Science

www.scu.edu.au/scps/
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