Backgrounder on Plant Genetic Resources and Plant Breeding

In the 10,000 years since humans first took up farming, our ancestors have sought food security by identifying, adapting and using plant genetic resources. As they made the transition from hunting and gathering to agriculture, those forebears encouraged the growth and production of certain favoured plant species -- plants valued for food, flavouring, ease of cooking, medicinal, religious and other purposes. (For information about such plants from the world's forests, see the FAO Forestry Department publication non-wood News; to receive a printed copy, send a message to non-wood-News@fao.org)

Before the modern era of "gene guns" used by laboratory plant breeders to transfer desirable new genes into designer crops, there was (and still is) the farmer in the field. The farmer assessed wild and cultivated plants for their strengths and weaknesses -- their nutritional or other value, their resistance to pests, disease and drought. The trick then, as now, is to bring out and mix desirable traits while minimizing the undesirable. Just what the most desirable traits are depends on the farmer, particularly on whether the farmer (who is as likely to be a woman as a man) practices commercial or subsistance farming. (See Women and Plant Genetic Resources for Food and Agriculture.)

As peoples have migrated, whether to take up new opportunities or due to war, civil strife or natural disasters, their plants have migrated with them. Exposure to new environments placed new selection pressures on the various species. Encounters with new and changing human cultures meant that plant species came to be valued for different purposes. One group of people might have encouraged the development of the food potential of the species, another might have refined it as a beverage. One might have used a grain for making bread, others might have selected types more amenable to mixing with water for a porridge, or roasting. A tree species might have been used for timber, fuel, food or shelter.

More on emigrant plants and people, below.

By 1859 when Darwin published "Variation under Domestication", the first chapter of The Origin of the Species, the world's major crops and other domesticated species were rich with diversity, a result of natural and human-influenced evolution over millenia:

• there was rice adapted to grow under metres of water and rice adapted to regions receiving only a tiny amount of rainfull annually.
• there were white potatoes, yellow, red, blue and black -- both inside and out.
• there were sorghums for bread, others for beer, still others with strong fibrous parts used for basketry, brooms and house construction.
• there was the diversity that is less apparent to the human eye -- genetic resistance to pests and diseases and other characteristics conferred by genes.

Global Share of Dietary Energy Supply from Different Plant Sources
Source: Report on the State of the World's Plant Genetic Resources, fig. 2.1 (available under the "More Reading" section.)

The migration and valuation of plant genetic resources accelerated at a dizzying speed in the 20th century. Development agencies, scientists and private corporations continue to search for ways to quickly boost food production in keeping with quantum leaps in the world population. Today they are counting on a "genetic Green Revolution" through which genetic engineering will lead to the development of plants suited to different stressful environments (e.g. drought-prone areas, saline soils), rather than using agro-chemicals and massive irrigation to adapt the environment to the plants as was the case in the past.

During the "Green Revolution" of the 1960s-1970s, modern varieties resulting from formal plant breeding carpeted farm fields around the world. Irrigation, pesticides, fertilizers and mechanization were the other ingredients which led to stupendous growth in farm yields. In terms of food security the world was able to keep up with population growth in places such as Asia. But uniformity is a double-edged sword: it made such large-scale, highly productive farming possible and was at the same time its Achilles heel. Use of modern varieties on a widespread scale meant that indigenous varieties had been pushed out. In many instances they have been lost forever.

"The chief contemporary cause of the loss of genetic diversity has been the spread of modern, commercial agriculture," according to the FAO document Report on the State of the World's Plant Genetic Resources. "The largely unintended consequence of the introduction of new varieties of crops has been the replacement -- and loss -- of traditional, highly variable farmer varieties. This process was the cause of genetic erosion most frequently cited in the Country Reports which form the basis of the State of the World report prepared for the Leipzig conference.

Recognition that the world has been losing its plant genetic heritage is not new. In the 1970s genebanks were constructed around the world to preserve ex situ millions of "accessions" (samples) of plant varieties. But many of those genebanks are rapidly deteriorating while natural, or in situ preservation of local varieties is threatened by the encroachment onto peasants' fields by modern varieties. The Report cites some examples of this loss of biodiversity:

• In China, of 10,000 wheat varieties in use in 1949, only 1,000 remained in use in the 1970s. In its national report in preparation for the Leipzig conference, China also noted losses of wild groundnut and wild rice.
• Of 7,098 varieties of apple documented as being in use in the United States between 1894 and 1904, about 86 per cent have been lost. The U.S. has also lost 95 per cent of the cabbage, 91 per cent of the field maize, 94 per cent of the pea and 81 per cent of the tomato varieties cultivated in the last century.
• More examples in sections #23-#29 in the Report on the State of the World's Plant Genetic Resources, available under the "More Reading" section.

Main causes of genetic erosion as cited in country reports
Source: Report on the State of the World's Plant Genetic Resources, fig. 1.1 (available under the "More Reading" section.)

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