Download Plants can suffer from infections caused by fungi, bacteria, viruses

Breeding Aims
Disease Resistance
Article is from http://www.gmo-compass.org/eng/agri_biotechnology/breeding_aims/148.disease_resistant_crops.html and modfied for
use in the classroom by A. Teague
Plants can suffer from infections caused by fungi, bacteria, viruses, nematodes, and other pathogens. Various
high-tech approaches have been proposed to protect plants from harmful afflictions. To date, most interest has
been focused on virus resistant transgenic plants, but using biotechnology to develop resistance to fungi,
bacteria, or nematodes has also gained attention.
Fighting fungal infections
Fungi are responsible for a range of serious plant diseases such as blight, grey mold,
bunts, powdery mildew, and downy mildew. Crops of all kinds often suffer heavy losses.
Late blight of potato is
caused by the
fungusPhytophtora
infestans, the disease
responsible for the great
Irish potato famine of
1846-47. It led to the
deaths of more than one
million people.
Fungal plant diseases are usually managed with applications of chemical fungicides or heavy metals.
In some cases, conventional breeding has provided fungus resistant plants.
In addition to preventing a loss of crops, preventing fungal infection keeps crops free of toxic
compounds produced by some fungi. These compounds, often referred to as mycotoxins, can affect
the immune system and disrupt hormone balances. Some mycotoxins can cause cancer.
Viral diseases
Viruses cause many economically important plant diseases. For example, the Beet necrotic yellow
vein virus (BNYVV) causes sugar beets to have smaller roots, reducing the amount of the crop by up
to 50 percent. The spread of most viruses is very difficult to control. Once infection begins, no
chemical treatment methods are available. Losses are usually very high. This translates into
considerable losses for farmers and customers pay more for the fruit or vegetable products.
Papaya ring
spotpotyvirus is a
serious viral disease of
papaya, which inhibits
photosynthesis and
Viruses are often transmitted from plant to plant by insects. Insecticides are sometimes used to
stunts growth. Virus
control viral infections, but success is very limited.
resistant GM papyas have
been developed (see
below).
Virus resistant GM plants
In some cases, biotechnology can be used to make virus resistant crops. The most common way of doing this is by giving a
plant a viral gene. The plant can then produce this viral protein before the virus infects the plant. If the virus arrives, it is not
able to reproduce.
The explanation for this is called cosuppression. The plant knows that the virus protein should not be produced and it will
eventually shut down the virus. When the virus tries to infect the plant, the production of proteins is already blocked.