Agriculture and Plant Genetics




Higher Nutrition, Lower Pollution


Weizmann Institute plant biologists are working on improving food crops while reducing the use of chemical fertilizers and herbicides.
Hybrid cucumber varieties with high resistance to viral disease have been developed at the Institute, as have the world's first hybrid melons based on specially-bred parent plants.
Together with experts from Egypt and the United States, an Institute team is fighting devastating parasitic weeds that threaten staple crops in the Middle East and Africa, while other Institute plant specialists are using genes from wild wheats native to the Fertile Crescent to achieve dramatic improvements in the nutritional value of cultivated wheats.
An Institute group is assessing the effect of the damaged ozone layer on the essential process of photosynthesis.


Agriculture and Plant Genetics

Higher-yield wheat


Agriculture and Plant Genetics


Weizmann Institute scientists developed innovative chromosomal engineering techniques and used them to transfer desired genes from wild emmer wheat, the wild progenitor of cultivated wheat, into cultivated wheat. This resulted in new varieties of common wheat (for bread) and durum wheat (for making pasta). Under certain conditions, some of these wheats provide up to a 40 percent higher yield than the original varieties. This achievement allows for the production of more wheat grains and wheat protein per growing area unit.


Hybrid wheat that's big, strong and high quality

Weizmann Institute scientists were the first to apply a genetic method to the production and maintenance of male-sterile-female lines. These lines enable the production of hybrid wheat lines. Hybrid wheat produces higher yield and better quality than the original varieties and is more resistant to diseases and other natural damage.


Survival in the harshest conditions

Plants and animals that are able to survive in extreme environmental conditions have developed special biological adaptation mechanisms in the course of evolution. An example is the single-cell alga, dunaliella; very similar to plants, it is able to survive in extremely harsh surroundings, such as highly saline water. Weizmann Institute scientists discovered some of the properties that allow dunaliella to exist under these difficult conditions.
Other discoveries shed new light on solar energy absorbing processes in plants, and on defenses against injury caused by exposure to light. In these defensive processes, dunaliella produces a very large quantity of beta carotene, which is often used as a human food supplement. Thanks to the Weizmann scientists' research, the dunaliella alga is being cultivated on a commercial scale and the beta carotene produced from it is being marketed in many countries, especially in Japan.


Increasing access to essential nutrients

Amino acids are the building blocks of proteins. Essential amino acids are those that our body cannot produce by itself and therefore must receive from external sources such as meat. Genetic engineering techniques developed at the Weizmann Institute enable increased production of essential amino acids in edible plants, improving their nutritional value. These studies may be of great help to people in developing countries where good protein sources are not widely available.


Wild tomatoes help crops resist wilt disease


Wild tomatoes help crops resist wilt disease


Weizmann Institute scientists discovered a gene originating in wild tomato plants which provides resistance against wilt disease. The isolated gene was inserted by genetic engineering techniques into the cultivated tomato plant genome. This made the engineered plant resistant to the disease. The exact identification of this gene will enable its accelerated introduction into cultivated plants using marker-based breeding methods. The presence of genes that provide plants with disease resistance may greatly decrease the need for spraying crops with pesticides, or treating soil which can cause environmental damage.
Wilt disease is caused by the penetration of a fungus called fusarium into the plant's food transport system. The fungus robs the food from the plant and secretes a poison that causes the plant cells to die, until the entire plant wilts. The natural evolution of wild tomato plants has resulted in an efficient defense system against fusarium that works in two main stages. The first stage is based on an "intelligence unit" that identifies the invading fungus and notifies the plant. In the second stage, after receiving this notification, the defense system secretes enzymes and other substances that destroy the fungus or prevent its encroachment.
Weizmann researchers discovered that the main part of the natural defense system still exists in cultivated tomato plants, but the plants are missing the so-called intelligence unit; without its warning, the system cannot begin to operate. The gene was isolated and cloned, and later inserted into the cultivated tomato plant genome, making it resistant to the blight-causing fusarium fungus.


Reducing weeds' staying power

Weizmann Institute scientists developed a novel strategy in the war against detrimental weeds, based on the combined activity of herbicides and a special preparation that impairs the weeds' regular resistance mechanism to herbicides. Greenhouse experiments demonstrated that this strategy allows the dose of several herbicides to be lowered. The strategy also delays the natural evolution of resistance to herbicides. This could contribute to significantly reducing the costs of producing agricultural crops, and it may also help to diminish the possibility of damaging effects from the widespread use of herbicides.
This innovative strategy was based on the researchers' insight into the function of metals in plants. It turns out that certain metals in the plant are required for the function of enzymes, which decompose lethal hydroxyl radicals induced by some herbicides. In light of this finding, the researchers developed organic compounds that selectively bind metals and remove them from those enzymes, effectively paralyzing the weeds' defense mechanism.


A strategy for parasitic weeds

Weizmann Institute scientists proposed an innovative solution to the problem of parasitic weeds such as witchweeds, which ravage grain and legume crops in several parts of the world, particularly in sub-Saharan Africa. An estimated 100 million farmers lose half their yield to these parasites. The method developed at the Institute relies on a new use for a certain type of corn that has been biotechnologically developed in the United States. This corn has a gene which confers resistance to a particular type of herbicide and is therefore unharmed when sprayed.
Rather than spraying entire fields, the scientists suggested taking seeds that are resistant to this herbicide and soaking them in it before planting. The herbicide then spreads through the germinating crop's roots and the surrounding soil, killing the parasites before or after they attach to the crop. By the time the crops ripen, the herbicide has disappeared and does not affect the food supply. The scientists' colleagues in Kenya at CIMMYT, the world-wide organization attempting to provide sustainable wheat and maize systems for the poor, have proven that the approach works and are readying local varieties with this gene for release to farmers.


Plants sing as they work

The sun is the primary source in the Earth's food and energy chain. Sunlight energy is trapped by the tiny organelles in green plants and used in photosynthesis to convert water and carbon dioxide into sugars and other organic energy-rich materials which we use for food and fuel. Photosynthesis produces the oxygen in the air, without which there is no life on this planet.
Weizmann Institute scientists contributed to the study of the various aspects of the complex process of photosynthesis. In some of these studies, they developed a unique method to measure photosynthesis, based on the detection of sound arising from within the plant leaf when light is rapidly shone on it. These sounds are the leaf's photosynthetic "exhalations," expelling oxygen in rationed portions, according to the rhythm of the flashing light. Part of the light energy shone on the leaf is converted to heat and is also expelled at periodic intervals, according to the tempo of the flashing light. Thus, thermal waves are formed and cause cyclical expansions and contractions that also produce sounds. Weizmann Institute scientists listened to these sounds, measured their strength and rhythm, and then calculated the scope of the photosynthetic process.
Plants sing as they work


True potato seeds

The production of true potato seeds, and especially hybrid seeds, is a goal in potato breeding. The reason: true potato seeds do not transmit major viral diseases to the next generation. To produce hybrid seeds efficiently, one of the parents (the seed parent) has to be made male-sterile. Researchers at the Weizmann Institute found a way to do this in potato plants.
They developed a method for transferring intracellular organelles (mitochondria or chloroplasts) from a donor to a recipient cell. The method is based on exposing the donor cell to gamma rays, which destroy its nucleus. The cell membranes of both the donor and the recipient are then decomposed by enzymes and the cells unite to form a hybrid which is capable of reproducing in cultures and even differentiating and developing into somatic-hybrid plants. In some of these plants the nucleus is that of the recipient, but organelles originate from the donor. This organelle incompatibility leads to male sterility.
The procedure has been adopted by the International Potato Center (CIP) in Lima, Peru, in their effort to supply elite, true hybrid seeds to farmers in developing countries.


Potato plants with a tolerance to bacteria

Weizmann Institute scientists are developing potato lines whose genome includes a gene of an insect that encodes a particular protein, which is a toxin. The toxin destroys different types of bacteria and does not injure higher species of animals. It is intended to provide potatoes with a defense against several bacterial diseases that infect either the roots or the tubers. This work is performed in collaboration with the International Potato Center (CIP) in Peru.


Cucumber seeds

In the 1950s, Weizmann Institute scientists were the first to find a way to produce hybrid cucumber seeds without hand pollination. This method is used today throughout the world.