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.

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 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 probably already happened in maize in Mexico)

Trends in diversity of crops from wild ancestors to modern cultivars Van der Wouw et al., 2009

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

Changes in spreads of crops worldwide Khoury et al., in prep

Decrease in heterogeneity between national diets Khoury et al., in prep

Change in crop spread and abundance in national diets, Khoury et al., in prep

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

Interspecific crop Diversity in the Compositae Interspecific crop diversity in the Compositae

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

SunflowerNougStevia (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

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

Taxonomic diversity and number of strongly domesticated crops Dempewolf et al Dempewolf et al Fabaceae Poaceae Rosaceae Solanaceae Compositae Rubiaceae Euphorbiaceae Melastomataceae Lamiaceae Orchidaceae Number of species Number of strongly domesticated crops

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?

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.

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

Conserving Crop Genetic Diversity in – situ conservationex – situ conservationvs.

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