Why Conserve Crop Genetic Diversity?

Why is crop genetic diversity is important and why are many of these plants are threatened?

Why is there a  downward trend in the diversity of the food that we eat and an associated reduction in crop genetic diversity, both in terms of cultivated plants (landraces) and the wild plants from which our crops originate (crop wild relatives)?

Crop genetic diversity: a critical resource

A wide range of genetic variation is needed within species to help them adapt to changing environment conditions and new pests and diseases.
The plants we use as crops (either directly as food or as fodder for animals) are dependent in terms of resilience and adaptability, on the broad genetic base of variation that exists both in the crops developed over millennia of farmer experimentation, and from their wild relatives.

Almost all modern varieties of crops have been improved using genetic diversity derived directly from a wild relative.

The Russian botanist Nikolai Ivanovich Vavilov recognised and championed the potential of crop wild relatives (CWR) for crop improvement in the 1920s and 1930s. Wild relatives were first routinely used by agricultural scientists to improve major crops in the 1940s and 1950s, and by the 1960s and 1970s this practice was leading to some major breeding successes.

Genes from wild relatives have been particularly important in providing resistance to pests and diseases. For example,
  • CWR of potatoes (Solanum spp.) have been used to improve cultivated varieties since the 1900s, when genes from the Mexican S. demissum were used to breed resistance against the fungus that causes potato blight.
  • During the 1970s, grassy-stunt virus severely reduced rice yields across Asia; after 4 years of research, during which over 17,000 cultivated and wild rice samples were screened, disease resistance was found in one population of Oryza nivara growing wild near Gonda in Uttar Pradesh, India. Resistant rice hybrids containing the wild Indian gene are now grown across Asia.
  • Also in the 1970s, the US maize crop was severely threatened by corn blight. The blight destroyed almost US$1,000 million worth of maize and reduced yields by as much as 50%. The problem was solved through the use of blight resistance genes from wild varieties of Mexican maize.

Genes from wild relatives can also improve crop performance. For example,
  • genes from a wild relative of the tomato have contributed to a 2.4% increase in solid content in commercial tomatoes. This increase has been valued as being worth approximately US$250 million in California alone.
  • A wild relative of wheat, Aegilops tauschii, has provided wheat with tolerance to drought, heat, salinity and water-logging, whilst another wild wheat relative, Triticum dococcoides, has improved nutritional qualities by increasing the protein content of durum wheat.

The dollar signs above are important and provide one reason why crop genetic diversity should be taken so seriously.

The US Government estimates that just a 1% gain in crop productivity means a US$1,000 million benefit to the American economy.

Genes from CWR have been used in at least 23 non-timber crops in the US and it has been estimated that between 1976 and 1980 wild species contributed US$340 million per year to the US farm economy in terms of yield increase and disease resistance.

Estimates of the global value associated with the use of plant genetic resources in food and agriculture vary from hundreds of millions to tens of billions of dollars per year. One estimate, for example, puts the annual value of products derived from the exploitation of plant genetic resources at US$500–800 billion.

Definitions

Landrace
A crop cultivar that evolved with and has been genetically improved by traditional agriculturalists, but has not been directly influenced by modern breeding practices.

Introgression
The permanent incorporation of genes from one set of differentiated populations (species, subspecies, races and so on) into another.

Cultivar
A variety of a plant produced and maintained by horticultural techniques and not normally found in wild populations.

CWR
Crop Wild Relative - a wild plant with a genetic relation to a cultivated crop.

During the 1970s, grassy-stunt virus severely reduced rice yields across Asia. After years of research, during which over 17,000 cultivated and wild rice samples were screened, disease resistance was found in one population of Oryza nivara growing wild in Uttar Pradesh, India. Resistant rice hybrids containing the wild Indian gene are now grown across Asia.

Subscribe to our mailing list

* indicates required