1. Plant of the Day Isoetes andicola
Lycophyte endemic to Peru at high elevations
Restricted to the edges of bogs and lakes
Leaves lack stomata and so CO2 is obtained from sediment via the roots
Carbon fixation occurs via the C3 pathway by day, but via a CAM-like process at night
Members of the quillwort family (Isoetaceae) are the nearest living relatives of the ancient “scale trees” (e.g. Lepidodendron)

2. Crop diversity

3. Big Questions Why is crop diversity/agrobiodiversity important?
What changes have occurred/are predicted to occur in global crop diversity?
What are the major threats to crop diversity?
What solutions do we have to these threats?

4. Crop diversity
Most crop species have lower genetic diversity than their wild progenitors due to the ‘domestication bottleneck’
However, crop species commonly harbor many distinct varieties and landraces that arose as a result of artificial, diversifying selection.

5. Crop diversity e.g. potatoes (Solanum tuberosum)
Single origin in Southern Peru (~10,000–7,000 years ago), diversifying selection for over 4000 varieties.

6. Major uses of crop diversity
Interspecific diversity (crop wild relatives) as well as intra-specific diversity are an important source for new alleles (such as disease resistance) in crop improvement efforts.

7. Where does the cultivated gene pool come from?
From last week:
Where does the cultivated gene pool come from?
Sclerotinia resistance locus
Wild Introgressions
H. petiolaris
H. argophyllus
H. annuus
landraces

8. Major uses of crop diversity
Interspecific diversity (crop wild relatives) as well as intra-specific diversity are an important source for new alleles (such as disease resistance) in crop improvement efforts.
Different landraces and varieties are often well adapted to their local/regional agro-ecological niche and are unique in many phenotypic traits, such as stress response/resistance.

9. Major uses of crop diversity
Interspecific diversity (crop wild relatives) as well as intra-specific diversity are an important source for new alleles (such as disease resistance) in crop improvement efforts.
Different landraces and varieties are often well adapted to their local/regional agro-ecological niche and are unique in many phenotypic traits, such as stress response/resistance.
Agro-biodiversity is thought to have the potential to play a major role in climate-change adaptations of agro-ecosystems

10. Global gridded crop models predict large reductions in yields of major crops (especially under nitrogen stress)
Rozenweig et al. 2014

11. Major uses of crop diversity
Interspecific diversity (crop wild relatives) as well as intra-specific diversity are an important source for new alleles (such as disease resistance) in crop improvement efforts.
Different landraces and varieties are often well adapted to their local/regional agro-ecological niche and are unique in many phenotypic traits, such as stress response/resistance.
Agro-biodiversity is thought to have the potential to play a major role in climate-change adaptations of agro-ecosystems
Indigenous people who cultivate much of the world’s traditional crop diversity have often unique knowledge about uses of such diversity unknown to western society

12. Major uses of crop diversity
Wild relatives of millet in Uganda
(Global Crop Diversity Trust)
Chuño, a variety of “freeze-dried” potato that can be stored long term

13. Major threats to crop diversity
Agricultural intensification and crop monocultures can lead to genetic erosion (loss of genetic diversity) in crops
An example of the “dispersal bottleneck” is in coffee, which was introduced into South America as a single tree.
Van der Wouw et al. 2009

14. Uptake of modern varieties
Van der Wouw et al. 2009

15. However, the evidence for a modernization bottleneck is equivocal
wheat
From a meta-analysis of 24 wheat and 20 non-wheat studies of crop genetic diversity through time.
Van der Wouw et al. 2010
non-wheat

16. Major threats to crop diversity
Agricultural intensification and crop monocultures can lead to genetic erosion (loss of genetic diversity) in crops
Crop replacement as dictated by the global marketplace or as development strategy can lead to the loss of entire crop species
The first three crops account for 50% of the calories and protein consumed worldwide, and along with another 27 species account for ~95% of the worlds’ food needs. Although there are at least 12,000 edible plants!

17. Changes in crop commodities worldwide
National food supplies contain more crop species (A & B),
slightly increased evenness of crop contribution to calories (C & D), and reduced dominance by a single crop (E & F) over the last 50 years
Khoury et al. 2014

18. Change in crop geographic spread in national diets, 1961–2009
All crops (except cottonseed oil) are contributing to food supply in an increasing number of countries
Khoury et al. 2014

19. Change in crop abundance (calories) in national diets, 1961–2009
Which crops do you think have had the highest increase in abundance?
The degree of increase in spread (see previous slide) predicts the abundance of crop species in national food supplies.
Khoury et al. 2014

20. Increase in homogeneity among national diets (crop contribution to calories), 1961–2009
Khoury et al. 2014

21. Change in number of countries in which maize, rice and wheat are being eaten
Khoury et al. unpublished

22. Interspecific crop diversity in the Compositae

23. Crop diversity in the Compositae
Ornamental
Gerbera x hybrida
Zinnia sp.
Seed oil
Helianthus annuus
Guizotia abyssinica
Phytochemicals
Parthenium argentatum
Artemisia sp.
Edible leaves
Lactuca sativa
Cichorium endivia
Tubers and roots
Helianthus tuberosus
Smallanthus sonchifolius
Dempewolf et al. 2008

24. Domestication is a process
The distinction ‘domesticated’ or ‘not domesticated’ is an over-simplification.
Some crops have moved along this process further than others… Why?
In order to be able to look at domestication at a broad scale (e.g. family wide), we need to be able to understand how this crop diversity is partitioned.
We can recognize different levels of domestication.
How can we decide which level?

25. Domestication index for Compositae crops
Sunflower
Noug
Stevia
(A) Phenotypic differentiation + –
(B) Extent of cultivation
(C) History of cultivation
(D) Major genetic alterations
(E) Improvement through major
breeding
Total score 4
 strong 2
 intermediate 1
 weak
Loss of SI is a major genetic alteration
Dempewolf et al. 2008

26. Level of domestication for major Compositae crops
Strongly domesticated:
sunflower (Helianthus annuus)
lettuce (Lactuca sativa)
safflower (Carthamus tinctorius)
endive (Cichorium endivia)
chicory (Cichorium intybus)
Semi-domesticated:
cardoon (Cynara cardunculus var. altilis)
globe artichoke (Cynara cardunculus var. scolymus)
noug (Guizotia abyssinica)
Jerusalem artichoke (Helianthus tuberosus)
Yacon (Smallanthus sonchifolius)
Weakly/not domesticated:
Stevia (Stevia rebaudiana)
Dempewolf et al. 2008

27. Taxonomic diversity and number of strongly domesticated crops
20 -
18 -
16 -
14 -
12 -
10 -
8 -
6 -
4 -
2 -
0 -
Fabaceae
Poaceae
Number of strongly domesticated crops
Rosaceae
Solanaceae
Compositae
Euphorbiaceae
Rubiaceae
Melastomataceae
Lamiaceae
Orchidaceae
5000
10000
15000
20000
25000
Number of species
Dempewolf et al. 2008

28. Why are there so few strongly domesticated crops in the Compositae?
Secondary compounds:
sequiterpene lactones, alkaloids and terpenoids
affect the palatability of a species or act as allergens
Nutritional considerations:
produce inulin rather than starch as storage carbohydrate; inulin is indigestible by the human gut
oils from Compositae species are high in unsaturated fatty acids, which carries health benefits but also makes the oil go rancid faster
Dempewolf et al. 2008

29. Why are there so few strongly domesticated crops in the Compositae?
Adaptive traits:
wind dispersal or dispersal by adhesion to animal fur is common; might limit seed and fruit size
Mating systems:
self-incompatible outcrossers; might reduce the probability of domestication
Preferences of early farmers:
defenses against herbivory (e.g. secondary compounds or spines/thorns)
early farmers probably focused on crops that could supply them with reliable sources of carbohydrates or proteins

30. Neglected and Underutilized Species
From top left clockwise: cherimoya (Annona cherimola), Oca tubers (Oxalis tuberosa), noug (Guizotia abyssinica), and ground nut (Vigna subterranea)

31. What are neglected and underutilized species?
At present, only 150 plant species are used and commercialised on a significant global scale
Over 50% of the world's requirement for protein and calories are met by only three: rice, wheat and maize.
There are an estimated 7,000 species that play a crucial role in poor people's livelihood strategies and may have a significant potential for commercialisation.
Alongside their commercial potential, many of the underutilised plant species also provide important environmental services, as they are adapted to marginal soil and climate conditions.

32. Underutilized Species have the potential to contribute to livelihood improvement by:
increasing incomes
ensuring food security
improving nutrition
enhancing biodiversity
tolerating stress conditions
occupying important ecological niches
production with low external inputs
stabilizing ecosystems
creating new markets

33. Conserving Crop Genetic Diversity
in – situ conservation
vs.
ex – situ conservation
What do you think are some benefits and drawbacks to each approach?

34. Global ex situ conservation
From Dulloo et al. 2010

35. An example of ex situ conservation
The ‘Doomsday’ vault
60 minutes piece on the Svalbard Global Seed Vault:

36. Unanswered Questions Will global diets continue to homogenize?
In highly developed countries, a diverse diet is often a signal of wealth.
Will our efforts to save genetic diversity of crops and wild relatives be enough?
To increase yield
To adapt to changing climates
What will be (or will there be) the next revolution in crop breeding?

37. “Adaptive drool in the gene pool”
High starch human diets are associated with increased copy number of AMY1, the salivary amylase enzyme gene
From Perry et al. 2007