This document discusses selenium (Se) deficiency in human populations and strategies for agronomic biofortification of staple crops to increase Se intake. It notes that Se deficiency can cause diseases and that intake requirements vary by individual. Agronomic biofortification trials adding selenate fertilizer have successfully increased the Se content of wheat, maize, cassava and other crops without affecting yields. Larger-scale trials are still needed to determine if this approach can meaningfully improve human health. Key challenges include low nutrient conversion efficiency from soil to grain and identifying sustainable application methods.

1. School of Agriculture, Food and Wine
Life Impact | The University of Adelaide Slide 0
Graham Lyons B Agric Sci, MPH, PhD
University of Adelaide, South Australia
Agronomic biofortification to reduce Se
deficiency in human populations:
achievements and challenges

2. School of Agriculture, Food and Wine
Life Impact | The University of Adelaide Slide 1
• Background: importance for health; variability in food
systems
• Genetic biofortification of Se in staple food crops: is
it feasible?
• Agronomic biofortification: summary of findings
• Finland: national Se biofortification
• Se-biofortified food products
• Challenges:
– Can large-scale Se agronomic biofortification
reduce the incidence of a major human disease?
– Low conversion efficiency in the field
– The need to conserve a valuable micronutrient
– Most efficient large-scale application method?
• Proposed African program
• Summary
Contents

3. School of Agriculture, Food and Wine
Life Impact | The University of Adelaide Slide 2
• Diverse selenoenzymes
• Profound deficiency: Keshan disease
and predisposal to Kashin-Beck disease
• Immune function
• Anti-ageing
• Reduces heavy metal toxicity
• Anti-viral, anti-cancer, anti-heart disease
effects
• Brain function
• Fertility
Why is Se important for humans?

4. School of Agriculture, Food and Wine
Life Impact | The University of Adelaide Slide 3
• RDIs in the 55-85 µg/day range
<40 too low and >200 may be too high
• Some researchers suggest that a Se status
of 120 µg/l in plasma is optimal in
protecting against cancer
• This should generally be achievable with an
intake of around 90-110 µg Se/day
How much Se do we need?

5. School of Agriculture, Food and Wine
Life Impact | The University of Adelaide

6. Distribution of Se deficient soils and two
diseases in China (adapted from Tan 2004)
Selenium deficiency/KBD/KD

7. School of Agriculture, Food and Wine
Life Impact | The University of Adelaide
Total soil Se is often unrelated to
plant-available Se
Location Total soil Se Se in wheat grain
µg/kg
Yongshou, China 700 20
Minnipa, SA 80 720
Charlick, SA 85 70
Dedza, Zimbabwe 30000 7

8. School of Agriculture, Food and Wine
Life Impact | The University of Adelaide
Environmental variability in wheat grain
Se at one site (S Australia, 2000)
Site Variety Rep
Grain Se
(µg/kg)
Bordertown Excalibur
1 120
2 110
3 690
4 520
Mean (se) = 392 (117)
Range = 110-690

9. Selenium in wheat:
enough genotypic variation to use in breeding ?
• Surveys & field trials of diverse germplasm in South Australia &
Mexico (total of 11 data sets)
• Se range 5 - 720 µg/kg, mostly 80 – 250 µg/kg
• Available soil Se is highly variable
• No genotypic variation in grain Se density detected among modern
wheat cultivars Rye & Aegilops tauschii may be higher for Se
accumulation in grain (Lyons et al, Plant Soil 2005; 269:369-380)
• Rice more promising, but is 55 v 35 µg/kg significant?
• GM for Se tolerance: selenocysteine methyltransferase from
Astragalus bisulcatus (Ellis et al, BMC Plant Biol 2004 Jan 28; 4:1)

10. School of Agriculture, Food and Wine
Life Impact | The University of Adelaide
Agronomic Se biofortification
field trials in South Australia
0
2
4
6
8
10
12
14
0 10 30 100 300
Selenate g/ha
GrainSemg/kg
Minnipa soil
Charlick soil
Minnipa foliar
Charlick foliar

11. Agronomic biofortification of cassava with Se, Zn, I
at CIAT, Colombia, South America

12. Harvest of biofortified cassava, Colombia

14. School of Agriculture, Food and Wine
Life Impact | The University of Adelaide
Potato
Soybean

15. School of Agriculture, Food and Wine
Life Impact | The University of Adelaide

16. School of Agriculture, Food and Wine
Life Impact | The University of Adelaide
Biofortified maize on the Loess Plateau

17. Se biofortification field trials on the Loess Plateau
• Spring: maize, soybean, potato, cabbage; winter: wheat, canola
• Relatively high Se application of 200 g/ha as selenate
• No effect on yield
• Biofortification by applying selenate to soil at planting was
highly effective in all crops studied (and in pot trials)
• Estimate that a Se target level of 300 µg/kg in grain can be
achieved by applying just 13 g Se/ha at planting
• Zinc and iodine biofortification by soil application was not
effective, except for cabbage

18. Field trial: Se concentrations in edible parts of crops
fold 118 80 126 159 450 6
maize soybean potato cabbage wheat canola
control 0.0106 0.022 0.012 0.082 0.01 0.011
Selenium plus 1.2561 1.751 1.511 13.029 4.5 0.07
0
2
4
6
8
10
12
14
Seconcentration(mgkg-1DW)

19. School of Agriculture, Food and Wine
Life Impact | The University of Adelaide Slide 18

20. Slide 19
Malawi Se-maize biofortification trials
2008-2010
Makoka site
Chilimba, Broadley et al, unpublished

21. Slide 20
1970: East Karelia had the highest CVD rates in the world
Low available Se in soils
Se supplementation of livestock feeds commenced
CVD (especially in men) began declining
1984: National Se biofortification program commences
1987: Se in spring wheat grain increases from 10 (pre-1984) to 250 µg/kg
Se intake in human diet trebles
Se in human plasma doubles (55 to 107 µg/l)
CVD continues to decline (but at same rate as before)
2010: CVD relatively low (due to less smoking, improved diet and exercise,
and possibly higher Se status)
No detrimental Se effects observed.
Se still added at 10 mg/kg in NPK
Finland: Se biofortification at a national level

22. School of Agriculture, Food and Wine
Life Impact | The University of Adelaide
Selenium benefits for plants
Se “not known to be essential”, but:
•Increased growth & tillering in rice (Wu et al, 1998)
•Increased tuber yield in potatoes (Turakainen et al,
2004)
•May stimulate chloroplastic cysteine desulphurases
(Pilon-Smits et al, 2002)
•Se + UVB increased growth in ryegrass & lettuce
(Xue & Hartikainen, 2000)
•Delayed senescence & increased growth in
soybeans (Djanaguiraman et al, 2005)
•Increased seed production and respiration in
Brassica (Lyons et al, 2009)
•Increased growth in mungbean associated with
upregulation of carbohydrate metabolism
enzymes (Malik et al, 2010)

23. School of Agriculture, Food and Wine
Life Impact | The University of Adelaide
Se-treated Brassica: 44% more seed

24. School of Agriculture, Food and Wine
Life Impact | The University of Adelaide
Se-biofortified wheat products in Australia
www.laucke.com.au

25. School of Agriculture, Food and Wine
Life Impact | The University of Adelaide
Se-biofortified wheat biscuits

26. School of Agriculture, Food and Wine
Life Impact | The University of Adelaide
Sprouting biofortification

27. School of Agriculture, Food and Wine
Life Impact | The University of Adelaide
Sprouting biofortification
• Rye germinated and grown for 5 days while
exposed to selenite
• Completely transformed into organic Se
• Can be blended to required Se level in flour
• 100% Se recovery
• Selenite may be more efficient than selenate for
this purpose
Bryszewska et al 2005; Food Additives and Contaminants
22(2): 135-140
Lintschinger et al 2000; J Agric Food Chem 48: 5362-5368

28. School of Agriculture, Food and Wine
Life Impact | The University of Adelaide Slide 27
• Can Se agronomic biofortification improve health of low-Se
groups/populations?
– In particular, can it reduce incidence/prevalence of any
important diseases?
• What is the most efficient large-scale application method?
– addition of selenate to fertiliser as in Finland?
– but only 12-18% Se recovery in grain, and we should not waste
this valuable micronutrient
– could fortify salt with selenite (along with iodine), as in China
• Applied Se usually does not increase yield, so why would farmers
use it?
– The simple answer is they wouldn’t
– But if trials demonstrate tangible benefits, there would be a
compelling argument for mandated Se addition to (subsidised)
NPK fertilisers in certain areas, e.g. in Sub Saharan Africa
Se agronomic biofortification: challenges

29. Slide 28
“Ecosystem services to alleviate trace element
malnutrition in Sub-Saharan Africa”
• Malawi & Zambia
• Includes soil mapping, dietary diversification, fertiliser/soil
amendment/intercropping trials (Se, Zn, I biofortification),
human feeding trials, economic analysis
• Sustainable conservation agriculture context
• At planning/application stage; alliances established; based on
successful Se agronomic biofortification trials with maize
(Chilimba et al)
• Led by Assoc Prof Martin Broadley, University of Nottingham
Proposed African study

30. Slide 29
• Se application (g Se ha-1)0246Grain Se (mg Se kg-1
DW)0.000.050.100.150.200.25MakokaChilimbaADC et
al.unpublished
• Malawi fertilisation experiments 2008-2010

31. School of Agriculture, Food and Wine
Life Impact | The University of Adelaide Slide 30
• Se is very important for human and animal
health
• Uneven distribution in soils and sub-optimal Se
status is common
• Agronomic biofortification of cereals and pulses
is quite easy and provides desirable,
bioavailable Se forms
• Application of selenate to soil at planting (e.g. in
fertiliser granules) is usually effective
• Challenges include finding if large-scale Se
biofortification in a low-Se region can improve
human population health, and finding ways to
improve application efficiency to reduce
wastage
Summary

33. School of Agriculture, Food and Wine
Life Impact | The University of Adelaide Slide 32
• Funders: HarvestPlus, International Fertilizer Industry
Assoc (IFA) & Prof Ismail Cakmak, Grains Research &
Development Corporation (Aust.), Laucke Flour
• Collaborators at Adelaide University (Prof Robin
Graham, James Stangoulis, Yusuf Genc), NWAFU,
Yangling, China (Prof Zhaohui Wang, Hui Mao et al),
CIAT, Cali, Colombia (Hernan Ceballos, Fernando Calle
et al)
• Encouragement from Jerry Combs, Howdy Bouis, Gary
Banuelos, Ismail Cakmak, Robin Graham, Martin
Broadley
• Editorial assistance from Ehsan Tavakkoli, Adelaide
University
• Waite Analytical Services (Teresa Fowles, Lyndon
Palmer et al), Adelaide University
Acknowledgement