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
0.4
0.6
0.8
1
1.2
1.4
1.6
1.8
0 -5 -10 -15 -20 -25 -30 -35
Latitude
Sp
ecie
s R
ich
nes
s /
km2
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
Sp
ecie
s R
ich
nes
s /
km2
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
Sp
ecie
s R
ich
nes
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
ecie
s R
ich
nes
s /
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