Plant of the DayIsoetes 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)

Crop diversity

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?

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.

Crop diversity

• e.g. potatoes (Solanum tuberosum)

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.

From last week:Where does the cultivated gene pool come from?

Sclerotinia resistance locusWild Introgressions

H. petiolaris

H. argophyllus

H. annuus

landraces

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.

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

Global gridded crop models predict large reductions in yields of major crops

(especially under nitrogen stress)

Rozenweig et al. 2014

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

Major uses of crop diversity

Chuño, a variety of “freeze-dried” potato that can be stored long term

Wild relatives of millet in Uganda(Global Crop Diversity Trust)

Major threats to crop diversity

• Agricultural intensification and crop monocultures can lead to genetic erosion (loss of genetic diversity) in crops

Van der Wouw et al. 2009

Uptake of modern varieties

Van der Wouw et al. 2009

However, the evidence for a modernization bottleneck is equivocal

From a meta-analysis of 24 wheat and 20 non-wheat studies of crop genetic diversity through time.

Van der Wouw et al. 2010

wheat

non-wheat

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

Changes in crop commodities worldwide

Khoury et al. 2014

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

Change in crop geographic spread in national diets, 1961–2009

Khoury et al. 2014

All crops (except cottonseed oil) are contributing to food supply in an increasing number of countries

Change in crop abundance (calories) in national diets, 1961–2009

Khoury et al. 2014

The degree of increase in spread (see previous slide) predicts the abundance of crop species in national food supplies.

Which crops do you think have had the highest increase in

abundance?

Increase in homogeneity among national diets (crop contribution to calories), 1961–2009

Khoury et al. 2014

Change in number of countries in which maize, rice and wheat are being eaten

Khoury et al. unpublished

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

• Transgene escape from GMOs to crop wild relatives and traditional landraces (has potentially already happened in maize in Mexico)

Interspecific crop Diversity in the CompositaeInterspecific crop diversity in the Compositae

Crop diversity in the Compositae

Dempewolf et al. 2008

Tubers and rootsHelianthus tuberosusSmallanthus sonchifolius

OrnamentalGerbera x hybridaZinnia sp.

Seed oilHelianthus annuusGuizotia abyssinica

PhytochemicalsParthenium argentatumArtemisia sp.

Edible leavesLactuca sativaCichorium endivia

• 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?

Domestication is a process

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

Domestication index for Compositae crops

Dempewolf et al. 2008

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)

Level of domestication for major Compositae crops

Dempewolf et al. 2008

Taxonomic diversity and number of strongly domesticated crops

5000 10000 15000 20000 250000

Fabaceae

Poaceae

Rosaceae

Solanaceae Compositae

RubiaceaeEuphorbiaceae

Melastomataceae Lamiaceae Orchidaceae

20 -

18 -

16 -

14 -

12 -

10 -

8 -

6 -

4 -

2 -

0 -

Number of species

Num

ber o

f str

ongl

y do

mes

ticat

ed c

rops

Dempewolf et al. 2008

• 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

Why are there so few strongly domesticated crops in the Compositae?

Dempewolf et al. 2008

• 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

Why are there so few strongly domesticated crops in the Compositae?

Neglected and Underutilized Species

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.

• 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

Underutilized Species have the potential to contribute to livelihood improvement by:

Conserving Crop Genetic Diversity

in – situ conservation ex – situ conservationvs.

Global ex situ conservation

From Dulloo et al. 2010

An example of ex situ conservation The ‘Doomsday’ vault

60 minutes piece on the Svalbard Global Seed Vault: http://www.cbsnews.com/videos/saving-seeds-in-doomsday-vault/

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?

“Adaptive drool in the gene pool”

From Perry et al. 2007

High starch human diets are associated with increased copy number of AMY1, the salivary amylase enzyme gene