Since ancient times, people have been fascinated by the beauty and diversity of the surrounding plants, especially flowers. Their aroma and tenderness in all ages has been the personification of love, purity, manifestation of feelings. Gradually, a person realized that he could not only enjoy the existing views of these beautiful creatures, but also take part in their formation. Thus began the era of plant breeding, leading to the production of new species with more necessary and important features in the geno- and phenotype. The two sciences working together on this issue have managed to achieve fantastic results so far - these are genetics and botany.
Botanical subject
Botany is the science that studies everything related to plants. That is them:
- morphology;
- genetics;
- physiology;
- anatomy;
- systematics.
This discipline covers all aspects of the life of representatives of the flora, from the internal processes of respiration, reproduction and photosynthesis to the external diversity of phenotypic traits.
This is one of the most ancient sciences, which appeared along with the development of man. Interest in the creatures growing around him, so decorating the surrounding space, has always been with a person. In addition, in addition to beauty, it has always been a powerful source of food, medicinal components, building material. Therefore, botany is a science that studies the most ancient, important, diverse and complex organisms on our planet - plants.
Plant breeding
With the passage of time and the accumulation of theoretical knowledge about the structure of these creatures from the inside, their way of life and the processes taking place in them, it became available to understand how to manipulate their growth and development. The science of genetics was gaining momentum, which made it possible to study different objects at the chromosomal level, cross them with each other, get good and bad results, and choose profitable and necessary ones. This was made possible by the following discoveries.
- Double fertilization in plants.
- Discovery of the processes of mitosis and meiosis.
- Development of crossing methods.
- The phenomena of heterosis, outbreeding and incubation.
- Deciphering the genetic code of plants.
- Biomolecular studies of cell and tissue composition.
- Discoveries in the field of cytology and histology.
Of course, these are not all the prerequisites that served as the beginning of a powerful movement and the development of plant breeding methods.
Crossing and its characteristics
Another process namecrosses - hybridization. The method of using this phenomenon is called hybridological. Gregor Mendel was the first to use it for his experiments. Every schoolchild knows his famous experiments on peas.
The essence of the whole process is to cross parental forms with each other in order to obtain heterozygous offspring, which will be called a hybrid. At the same time, different types of crossing have been developed. They are selected taking into account the individual characteristics of the variety, species or genus. There are two main types of such processes.
- Outbreeding, or outbreeding. Implies that the initial parent forms do not belong to the same species, genus or variety. That is, they are not related. Such crossing is one of the most popular and most often leads to heterosis when breeding pure lines.
- Inbreeding, or inbreeding - closely related hybridization of individuals belonging to the same species or genus, variety. This method is used to fix a useful trait in a population, including a phenotypic one. With repeated correctly carried out incubation, it is possible to obtain genetically pure plant lines.
These types of crossing have narrower varieties within themselves. So, one of the forms of outbreeding is crossbreeding - hybridization between varieties.
In addition to types, there are also different types of crossing. They were described and studied in detail by Mendel, Thomas Morgan and other geneticists of the past centuries.
Viewscrossbreeding
There are several main types of hybridization of individuals.
- Monohybrid, or simple. It implies the crossing of parental forms with the first offspring, carried out once.
- Dihybrid - based on parents that differ in two pairs of characteristics.
- Returnable - a hybrid from the first generation is crossed with the original parent.
- Polyhybrid, or double - individuals of the first generation are then crossed with each other, and subsequent ones with other varieties and species.
All the indicated varieties have a meaning in each specific situation. That is, for some plants, a simple crossing is enough to get the desired result. And for others, complex phased polyhybrid hybridization is required to obtain the desired trait and consolidate it in the entire population.
Hybrids of different generations
As a result of any crossing, this or that offspring is formed. The traits that it has taken from its parents can manifest themselves to varying degrees.
Thus, the signs of hybrids of the first generation are phenotypically always uniform, which is confirmed by Mendel's law (first) and his experiments on peas. Therefore, it is often the monohybrid type of hybridization that is used to obtain the same result, which is required only at a time.
Further on, all subsequent individuals already combine properties in themselves, so splitting appears in certain ratios. Recessives appear, mutational processes interfere. Therefore, the most important for industrial activityman, his agriculture, is precisely the first generation of plants received.
Typical example: if the goal is to produce only yellow tomatoes as a result of one seasonal period, then a yellow and a red tomato should be crossed, but the red should be obtained earlier from the yellow parent. In this case, the first generation will certainly be uniform - yellow tomato fruits.
Interspecific hybrids: characteristics
Interspecific hybrids are those that are obtained as a result of outbreeding or distant crossing. That is, this is the result of mating individuals belonging to different species in order to obtain a new one with predetermined characteristics and properties.
In this way, many important agricultural and ornamental plants were obtained in industry, and many new species of individuals were bred in animal breeding.
Examples of similar organisms
Examples of interspecific hybrids among plants:
- feed wheat;
- triticale - wheat and rye;
- rye-wheatgrass forms;
- wheat-elimus;
- several types of tobacco and others.
If we talk about animals, then also a lot of representatives can be cited as an example:
- hines (horse and donkey);
- ligr - lion and tigress;
- mezhnyak - black grouse and capercaillie and others.
The main problem with such hybridizations is that the offspring are either sterile orunviable. That is why people have created and developed a lot of ways to eliminate these factors. After all, if the desired result is obtained, then it is very important not only to fix it, but also to introduce the production of such organisms into the system.
What causes infertility in interspecific hybrids?
The causes of such problems lie in the processes of meiosis and mitosis, namely in anaphase, when the chromosomes diverge to the poles of the cell. At this moment, each of them is looking for its homologous pair. This is how whole chromosomes are formed from chromatids and the general karyotype of the organism is formed.
But in those individuals in which the merger occurred from different parental forms, the possibility of meeting such structures is minimal or impossible. That is why a random combination of traits occurs and as a result, individuals become infertile or unviable. That is, genes, in fact, become incompatible.
If we turn to the molecular level and find out what is the reason for the infertility of interspecific hybrids, the answer will be this: it is the incompatibility of DNA sections from the cell nucleus and mitochondria. As a result, there is no chromosome conjugation in the meiotic process.
This leads to disastrous results both in plant breeding and in crossing and breeding breeds and new animal species. Especially often this happens in representatives of the flora. Therefore, you can get a crop of hybrid plants only once, which is extremely inconvenient for the development of agriculture.
After it became clear to scientists what is the cause of interspecies infertilityhybrids, active work began to find a way to eliminate these causes. This led to the creation of several ways to eliminate the sterility of individuals.
Ways to overcome infertility
The main path chosen by biologists to solve this problem is the following. At the stage of meiosis, when the chromosomes diverge towards the poles of the cell, a special substance, colchicine, is introduced into it. It promotes the dissolution of the spindle fibers (cell center). As a result, all chromosomes remain in one cell, and do not fall into different ones. Now free conjugation between homologous pairs is possible, which means that the process of meiosis is quite normal in the future.
Thus, the offspring becomes fertile and easily bears fruit in the future when crossed with different forms. Most often, this method is used in plant breeding, it is called polyploidy. It was first applied by our scientist Karpechenkov. So he got the first fertile hybrid of cabbage and radish.
What is the reason for the infertility of interspecific hybrids, we have already found out. Knowing the nature of the problem, we managed to create two more ways to solve it.
- Plants pollinate with pollen from only one parent. This method allows you to get several generations of hybrid individuals, fertile. However, then the trait still returns, and the individuals become sterile again.
- Pollination of hybrids in the first generation with pollen from parents.
Today, more methods of struggle have not been created, but work is underway in this direction.
Lilies and their hybrids
Symbol of purity and innocence, flowerssadness and sorrow for the departed, gentle and subtle representatives of lilies - lilies. These plants have been valued by man for many centuries. During this time, no varieties have been created! Naturally, interspecific crossings affected them too.
The result was the development of nine groups of hybrid varieties that simply amaze with the beauty of phenotypic traits! Among them, a special place is occupied by the two most unusual and sought-after representatives:
- oriental hybrids;
- lilies OT hybrids.
Let's consider the signs of both groups and give them a description.
Oriental hybrids
This is the largest hybrid in terms of flower formation. Their biology is practically no different from that of other representatives. The dimensions of the growing calyx can reach 31 cm in diameter, and the color can be different. The Nippon variety is very beautiful, having large white flowers with a pink border. Their petals are corrugated.
The height of these plants ranges up to 1.2 m. This allows them to be planted at a distance of 20-25 cm from each other and form beautiful flowering ridges. All representatives of this group exude a very strong aroma.
Orienpits
This is the OT-hybrids lilies, the abbreviation of which is formed from the full name: oriental-tubular forms. They are also called lily trees for their very tall plant size and large flowers. On one stem up to 2.5 meters high, over 25 large (up to 30 cm) flowers can form, which are very fragrant and brightly colored.
This allows this group of hybrids to be very popular among gardeners, although not everyone can cope with their breeding. Very careful care and proper planting are required so that such forms can take root and produce offspring.
Sunflower and its hybrid forms
Sunflower hybrids differ from each other in terms of seed ripening. So, allocate:
- early (up to 90 days);
- early ripe (up to 100 days);
- mid-season (up to 110 days).
Seeds hybrids also give different. Oil content and yield are excellent and depend on the ripening period. The longer the plant is in the ground, the higher the quality of the crop. You can name some of the world's most common hybrids of this plant, the most in demand in agriculture.
- Tunka.
- Bosphorus.
- Rocky.
- PR64A15.
- Jason.
- Forward.
Among their main benefits:
- drought tolerance;
- diseases and pests;
- yield;
- high quality seeds;
- good fruiting.
