The critical role of crop wild relatives in ensuring long-term food security and their need

for conservation

Andy Jarvis, Julián Ramírez, Nora Castañeda, Nigel Maxted, Robert Hijmans and Jacob Van Etten

© Neil Palmer (CIAT)

The foundation of agriculture

Wild relatives of crops• Include both progenitor species and closely related species of cultivated

crops• Faba beans – 0 wild relatives• Potato – 172 wild relative species• Increasingly useful in breeding, especially for biotic resistance

Photos from Jose Valls, CENARGEN

Conserved ex situ in genebanks

Credit: Caperton27/FLICKR

Credit: CIATCredit: Global Crop Diversity Trust

Credit: IRRI

The Svalbard Global Seed Vault

Credit: Kitsune Noir/FLICKR

Why conserve CWR diversity?

• Use: 39% pest resistance; 17% abiotic stress; 13% yield increase

• Citations: 2% <1970; 13% 1970s; 15% 1980s; 32% 1990s; 38% >1999

Use!!

234 papers cited

Maxted and Kell, 2009

Florunner, with no root-knot nematode resistance

COAN, with population density of root-knot nematodes >90% less than in Florunner

Wild relative species

A. batizocoi - 12 germplasm accessions

A. cardenasii - 17 germplasm accessions

A. diogoi - 5 germplasm accessions

Uses in crop breeding

Credit: .Bambo./FLICKR

PapaSolanum tuberosum

Solanum bulbocastanum

Resistencia a Gota (Phythophtora infestans)

X

Grassy stunt virus in riceResistance from Oryza nivara genes(Barclay 2004)

Potato late blightResistance from Solanum demissun and S. stoloniferumNational potato council (2003)

Nevo and Chen 2010

Adaptation to abiotic stress

Quality traits

Post harvest deterioration - Cassava

Courtesy of Emmanuel Okogbenin

• Value as wild plant species in natural ecosystems

• Value of CWR as actual or potential gene donors:– US$340 million a year in US (Prescott-Allen and

Prescott Allen, 1986)– $20 billion toward increased crop yields per

year in the United States and $115 billion worldwide (Pimentel et al., 1997)

– US$10 billion annually in global wholesale farm values (Phillips and Meilleur, 1998)

Why conserve CWR Diversity?

• Individual examples of use:– Lycopersicon chmielewskii sweetening tomato US $ 5-8million per year

(Iltis, 1988)– Various CWR of wheat provide disease resistance to wheat and US

benefits by US $ 50m per year (Witt, 1985)

Courtesy of Nigel Maxted

Threats

Impact of climate change on CWR• Assessment of shifts in distribution

range under climate change• Wild potatoes• Wild African Vigna• Wild peanuts

Latitudinal and Elevational Shifts

Peanuts• Shift south and upwards

0

0.2

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0 -5 -10 -15 -20 -25 -30 -35

Latitude

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Current Richness

Future Richness (unlimited dispersal)

Future Richness (no dispersal)

A - Peanut

0.00

0.20

0.40

0.60

0.80

1.00

1.20

1.40

1.60

-200 300 800 1300 1800 2300

Elevation

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Current Richness

Future Richness (unlimited dispersal)

Future Richness (no dispersal)

B - Peanut

Latitudinal and Elevational Shifts

Potatoes• Shift upwards

0

0.2

0.4

0.6

0.8

1

1.2

45 40 35 30 25 20 15 10 5 0 -5 -10 -15 -20 -25 -30 -35 -40

Latitude

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s /

km2

Current Richness

Future Richness (unlimited dispersal)

Future Richness (no dispersal)

C - Potato

0.00

0.50

1.00

1.50

2.00

2.50

3.00

3.50

4.00

0 500 1000 1500 2000 2500 3000 3500 4000 4500 5000 5500

Elevation (m)

Sp

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km2

Current Richness

Future Richness (unlimited dispersal)

Future Richness (no dispersal)

D - Potato

Summary Impacts

• 16-22% (depending on migration scenario) of these species predicted to go extinct

• Most species losing over 50% of their range size• Wild peanuts were the most affected group, with 24

to 31 of 51 species projected to go extinct • For wild potato, 7 to 13 of 108 species were

predicted to go extinct• Vigna was the least affected of the three groups,

losing 0 to 2 of the 48 species in the genus

Florunner, with no root-knot nematode resistance

COAN, with population density of root-knot nematodes >90% less than in Florunner

Wild relative species

A. batizocoi - 12 germplasm accessions

A. cardenasii - 17 germplasm accessions

A. diogoi - 5 germplasm accessions

SpeciesChange in area

of distribution (%)Predicted state

in 2055

batizocoi -100 Extinctcardenasii -100 Extinctcorrentina -100 Extinctdecora -100 Extinctdiogoi -100 Extinctduranensis -91 Threatenedglandulifera -17 Stablehelodes -100 Extincthoehnii -100 Extinctkempff-mercadoi -69 Near-Threatenedkuhlmannii -100 Extinctmagna -100 Extinctmicrosperma -100 Extinctpalustris -100 Extinctpraecox -100 Extinctstenosperma -86 Threatenedvillosa -51 Near-Threatened

Impact of Climate Change – Wild Peanuts

More immediate threats….

Adapted from Nature, v.466, p.554-556, 2010

Concentration of the natural distribution on the area of most intensive cattle-raising and crop production activity in Brazil has not been a serious problem, in the past, for preservation of local wild species of Arachis, but the advance of the modern, mechanized agriculture, in the last few decades, and specially the use of herbicides have imposed severe pressure on wild populations. This is also true for Eastern Bolivia, where many species of section Arachis occur.

Slide provided by Jose Valls, CENARGEN

Slide provided by Jose Valls, CENARGEN

How well conserved are crop wild relatives?

Gap Analysis

© Neil Palmer (CIAT)

Why Gap Analysis?

• Tool to assess crop and crop wild relative genetic and geographical diversity

• Allows detecting incomplete species collections as well as defining which species should be collected and where these collections should be focused

• Assesses the current extent at which the ex situ conservation system is correctly holding the genetic diversity of a particular genepool

To know what you don’t have, you first need to know what you do have

The visible global system

The Gap Analysis process

Proxy for:

• Range of traits

Proxy for:

• Diversity

• Possibly biotic traits

Proxy for:

• Abiotic traits

• Identifying gaps

The Gap Analysis pathway

Taxonomy review Data gathering Georeferentiaton

Environmental

data gathering

Gap Analysis

process

Final

recommendations

An example in Phaseolus

Herbarium versus germplasm: Geographic

Herbarium versus germplasm: Taxon

Conserved ex situ richness versus potential

Priorities: Geographic and taxonomic

“Validation”: The man versus the machine

Model priorities versus expert priorities

Gap Analysis

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Taxon-level and genepool level priorities

Wild Vigna collecting priorities

• Spatial analysis on current conserved materials

• *Gaps* in current collections

• Definition and prioritisation of collecting areas

• 8 100x100km cells to complete collections of 23 wild Vigna priority species

Exploration and ex-situ conservation of Capsicum flexuosum

• Uncommon species of wild chilli, found in Paraguay and Argentina

• 18 known registers of the plant

• 2 germplasm accessions conserved in the USDA

• Genetically unknown

• Found in an area undergoing high levels of habitat loss

Capsicum flexuosum - FloraMap

Habitat: Forest Margins

Road Access

Priority Areas for Collection

Results

• 6 new collections of C. flexuosum

• 160 seeds conserved ex situ

• One plant found with few seeds, where previous herbarium record

• First accession conserved ex situ 1998

2001

2002

• 1 plant found, with few seeds

Using GIS model

Conclusions

• Massive importance of CWR• Use of these genetic resources on the increase• But not conserved ex situ and under threat in

situ• Need for a major collecting effort to fill gaps,

and explore novel genetic approaches to further stimulate their use

a.jarvis@cgiar.org