Using crop genetic diversity to combat pests
and diseases in agriculture
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 et
al., 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.
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