Lyons agronomics

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



• 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 biofortificationreduce 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



• 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?



• 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?


Life Impact | The University of Adelaide

Distribution of Se deficient soils and two diseases in China (adapted from Tan 2004)

Selenium deficiency/KBD/KD



Total soil Se is often unrelated toplant-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



Environmental variability in wheat grain

Se at one site (S Australia, 2000)

Site Variety RepGrain Se

(µg/kg)

Bordertown Excalibur

1 120

2 110

3 690

4 520

Mean (se) = 392 (117)

Range = 110-690

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)

http://www.adelaide.edu.au/vi/downloads/logo.html



Agronomic Se biofortification

field trials in South Australia

0

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0 10 30 100 300

Selenate g/ha

Gra

in S

e m

g/k

g

Minnipa soil

Charlick soil

Minnipa foliar

Charlick foliar

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

Harvest of biofortified cassava, Colombia



Potato

Soybean





Biofortified maize on the Loess Plateau

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

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

Se

con

cen

tra

tio

n (

mg

kg

-1D

W)



Slide 19

Malawi Se-maize biofortification trials

2008-2010

Makoka siteChilimba, Broadley et al, unpublished

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



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)



Se-treated Brassica: 44% more seed



Se-biofortified wheat products in Australia www.laucke.com.au



Se-biofortified wheat biscuits



Sprouting biofortification



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 Contaminants22(2): 135-140

Lintschinger et al 2000; J Agric Food Chem 48: 5362-5368



• 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

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

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



• 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



• 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

Education

Lyons agronomics