The Environmental Food Crisis

Each year farmers experience significant crop losses as a result

of disease and pest infestation. These losses can be intensified

by changes in climatic conditions. To cope with pest and disease

problems, modern agriculture depends to a great extent on the

use of pesticides and the continuing production of new crop va-

rieties with specific resistance genes, although the value of inte-

grated pest management techniques and biological control are

increasingly recognized. Other ways of increasing productivity

while reducing dependence on pesticides are essential for in-

creasing productivity in sustainable ways.

Traditional crop varieties are a primary source of new resistant

germplasm for both farmers and breeders. These crop varieties

often contain a number of different resistance genes and resis-

tance mechanisms against a range of pests and diseases. In many

regions of the world, farmers have local preferences for growing

mixtures of varieties, which they understand provide resistance

to local pests and diseases and enhance yield stability. Within-

crop diversity through the use of variety mixtures, multilines or

the use of different varieties in the same production environment

has been found to reduce disease incidence and increase produc-

tivity without the need for pesticides.

Small-scale farmers in developing countries continue to depend

on local genetic diversity to maintain sustainable production and

meet their livelihood needs. Loss of genetic choices, reflected as

the loss of traditional crop varieties, therefore diminishes farm-

ers’ capacities to cope with changes in pest and disease infec-

tion, and leads to yield instability and loss. Intra-specific diversity

can be used to reduce crop damage from pest and diseases today

and for maintaining levels of diversity against future crop loss,

that is, crop populations that have less probability that migra-

tions of new pathogens or mutations of existing pathogens will

damage the crop in the future.

In China, interplanting 2 varieties of rice has been found to have

significant effects on disease incidence and productivity (Zhu

., 2000) and is now being used in 3 different provinces on thou-

sands of hectares. A global project supported by UNEP and the

Global Environment Facility is under way in China, Ecuador, Mo-

rocco and Uganda to develop ways in which farmers can use this

approach to combat diseases in crops such as bananas, barley,

faba beans and rice.

Using crop genetic diversity to combat pests

and diseases in agriculture