Principles of Plant Genetics and Breeding

Purpose and expected outcomes
Climate is the variation in meteorological factors over a large area formed over many years. It determines plant
adaptation to a growing region. Weather on the other hand is the environmental condition described by the shortterm
variations in meteorological factors within a local area. It determines crop development and productivity.
Weather affects the choice of specific crop production activities (i.e., how the crop is produced in the field). Plant
breeders usually develop breeding programs to produce cultivars for specific production regions. Crop production
is subject to the vagaries of the weather. Unpredictable weather can drastically reduce crop yield. Crop varieties
used in regions that are prone to adverse weather during production need to have the capacity to resist or tolerate
environmental stresses to an extent that they produce acceptable economic yield. After completing this chapter, the
student should be able to:
1 Describe the types of environmental stresses that reduce plant performance in crop production.
2 Discuss breeding for drought resistance.
3 Discuss breeding for cold tolerance.
4 Discuss breeding for salt tolerance.
5 Discuss breeding for resistance to heat stress.
6 Discuss breeding for tolerance to aluminum toxicity.
7 Discuss breeding for tolerance to oxidative stress.
8 Discuss breeding for resistance to water-logging.
Importance of breeding for resistance to
abiotic stresses
Only about 30% of the earth is land. Of this, about 50%
is not suitable for economic crop production, mainly
because of constraints of temperature, moisture, and
topography. Of the remaining portion of arable land,
optimum production is further limited by a variety of
environmental stresses, requiring mineral and moisture
supplementation for economic crop production. As the
world population increases more food will have to be
produced by increasing the productivity of existing
farmlands as well as bringing new lands into production.
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Breeding for resistance to
abiotic stresses
This means, marginal lands will have to be considered.
Plants breeders will have to develop cultivars that are
adapted to specific environmental stresses. It is estimated
that abiotic environmental stresses are responsible for
about 70% of yield reduction of crops in production.
In modern agricultural production, producers (especially
those in developed countries) are able to alleviate
moisture stress by providing supplemental irrigation.
Also, fertilizers are used to alleviate nutritional stress,
while soil reaction (pH) can be modified by applying
soil amendments such as lime or sulfur. Excessive soil
moisture can be removed by installing drainage systems.
However, in poor regions of the world where such