Hybrids are ... Crossing plants. Interspecific hybrids

The most promising approach to solving the world food problem is, apparently, further improvement of existing crops grown on already developed lands. Hybrids are something that can play a key role in providing food. After all, most of the areas suitable for farming are already occupied. At the same time, increasing the amount of water, fertilizers and other chemicals used on them in many places is economically impossible. This is why the improvement of existing crops is of exceptional importance. And hybrids are plants obtained as a result of such an improvement.

Protein content

The task is not only to increase the yield, but also to increase the protein and other nutrient content. For a person, the quality of proteins in edible plants is also very important : animals (including humans) must receive from the food the necessary quantities of all essential amino acids (that is, they are not capable of synthesizing themselves). Eight of the 20 amino acids a person needs come with food. The remaining 12 can be worked out by him. However, plants with a protein composition that is improved as a result of selection inevitably require more nitrogen and other nutrients than the original forms, so they can not always be grown on barren lands where the need for such crops is particularly high.

New Properties

Quality includes not only the yield, composition and quantity of proteins. Varieties that are more resistant to diseases and pests are created, due to the secondary metabolites contained in them, which are more attractive in shape or color (for example, apples of bright red color), better able to withstand transportation and storage (for example, hybrids of high-yielding tomatoes), and They have other properties essential for a given culture.

Activity of breeders

Breeders carefully analyze the available genetic diversity. For several decades they have brought out thousands of improved lines of the most important agricultural plants. As a rule, thousands of hybrids have to be received and evaluated in order to select those few of them that really will outperform their already widely-cultivated properties. For example, the yield of corn in the US from the 1930s to the 1980s. Increased almost eight times, although only a small part of the genetic diversity of this culture was used by breeders. There are more and more new hybrids. This allows more efficient use of planted areas.

Hybrid corn

Increasing the productivity of corn was made possible mainly through the use of hybrid seeds. Inbred lines of this culture (hybrid by origin) were used as parental forms. From the seeds obtained as a result of crossing between them, very powerful hybrids of maize develop. Crossed lines are sown in alternating rows, and panicles (male inflorescences) are manually cut from the plants of one of them. Therefore, all the seeds on these specimens turn out to be hybrid. And they have very useful properties for a person. By carefully selecting inbred lines, powerful hybrids can be obtained. These are plants that will be suitable for growing in any desired locality. Because the signs of hybrid plants are the same, they are easier to clean. And the yield of each of them is much higher than that of unimproved specimens. In 1935, maize hybrids accounted for less than 1% of the total crop grown in the United States, and now virtually all. Now the receipt of much higher yields of this crop is much less laborious than before.

Successes of international breeding centers

Over the past few decades, a lot of effort has been made to increase the yield of wheat and other grains, especially in warm climate zones. Impressive successes have been achieved in international breeding centers located in the subtropics. When new hybrids of wheat, corn and rice were grown in Mexico, India and Pakistan, this led to a sharp increase in the productivity of agriculture, which was called the Green Revolution.

Green revolution

The methods of selection, fertilization and irrigation developed during it were used in many developing countries. Each crop requires high growth conditions to produce high yields. The introduction of fertilizers, mechanization and irrigation are indispensable components of the Green Revolution. Because of the nature of the distribution of loans, only relatively wealthy landowners were able to grow new plant hybrids (grains). In many regions, the Green Revolution accelerated the concentration of land in the hands of the few wealthiest owners. Such a redistribution of property does not necessarily provide the majority of the population of these regions with work or food.

Triticale

Sometimes traditional methods of breeding can lead to surprising results. For example, a hybrid of wheat (Triticum) and rye (Secale) triticale (the scientific name Triticosecale) is becoming increasingly important in many areas and appears to be very promising. It was obtained by doubling the number of chromosomes in a sterile hybrid of wheat and rye in the mid-1950s. J. O'Mara at the University of Poz. Iowa with colchicine, a substance that prevents the formation of a cell plate. Triticale combines high yield of wheat with unpretentiousness of rye. The hybrid is relatively resistant to linear rust - fungal disease, which is one of the main factors limiting the yield of wheat. Further crosses and selection gave improved triticale lines for specific areas. In the mid-1980s. This culture, thanks to its high yields, resistance to climatic factors and fine straw that remains after harvesting, quickly gained popularity in France, the largest grain producer within the EEC. The role of triticale in the human diet is growing rapidly.

Preservation and use of genetic diversity of crops

Intensive programs of crossing and selection lead to a narrowing of the genetic diversity of cultivated plants on all their grounds. For quite understandable reasons, artificial selection is mainly aimed at increasing crop yields, and amongst the very homogeneous offspring of specimens selected strictly for this feature, resistance to disease is sometimes lost. Within the culture, the plants become more monotonous, since certain of their characteristics are more pronounced than the rest; Therefore, crops as a whole are more vulnerable to pathogens and pests. For example, in 1970, helminthosporiosis, a fungal corn disease caused by the species Helminthosporium maydis (pictured above), destroyed approximately 15% of the crop in the United States, with losses of approximately $ 1 billion. These losses, apparently, are due to the appearance of a new mushroom race, which is very dangerous for some of the main lines of maize, which were widely used in the production of hybrid seeds. In many commercially valuable lines of this plant, the cytoplasm was identical, since identical pistillate plants were repeatedly used in the production of hybrid maize.

To prevent such damage, it is necessary to grow isolated and preserve various lines of important crops that, even if the sum of their characteristics is not of economic interest, can contain genes useful in the ongoing struggle against pests and diseases.

Hybrids of tomatoes

Striking successes in increasing genetic diversity due to the involvement of wild-growing forms were achieved by tomato breeders. The creation of a collection of lines of this culture, carried out by Charles Rick and his staff at the University of California, Davis, has effectively dealt with many of her serious diseases, in particular, caused by imperfect fungi and Fusarium and Verticillum, as well as some viruses. The nutritional value of tomatoes was significantly increased. In addition, plant hybrids have become more resistant to salinity and other unfavorable conditions. This was mainly due to the systematic collection, analysis and use of wild-growing tomato lines for breeding.

As you can see, interspecies hybrids are very promising in agriculture. Thanks to them you can improve the yield and quality of plants. It should be noted that crossing not only in agriculture, but also in livestock breeding. As a result, for example, a mule appeared (the photo is presented above). This is also a hybrid, a cross between an ass and a mare.