Plant crossing - crossing technology and advantages of hybrid varieties. Crossing plant species

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It is known that the vast majority of plants and animals reproduce sexually. Their seed offspring arises only as a result of fertilization - the fusion of male and female reproductive cells, giving rise to new organisms.
Unlike vegetative method reproduction (by tubers, cuttings, buds, etc.), in which growing organisms continue their development from the stage to which the development of the tissue of the mother bush taken for their production has reached; during sexual reproduction, a fertilized egg - the zygote gives rise to a new plant, beginning its development again.
The process of fertilization has enormous biological significance, since thanks to it, developing new organisms acquire dual heredity - maternal and paternal, and as a result, greater vitality, which manifests itself in their better adaptability to various conditions external environment.
According to Lysenko, the biological role of the fertilization process is that by combining the female and male reproductive cells, which differ to a certain extent in their hereditary properties, into one cell and merging their two nuclei into one nucleus, the inconsistency of the living body is created, which is the cause of self-development, self-motion, etc. i.e. the life process with its inherent metabolism.
Artificial crossing of different varieties of plants and animal breeds is widely used in breeding practice.
The decisive moments in the development of new highly productive varieties of plants and animal breeds from the standpoint of materialistic Michurin biology are the intelligent and skillful selection for crossing of the original parental pairs and the further control of the emerging nature of the hybrid offspring by regulating living conditions.

Through many years of persistent practical work, which has a deeply substantiated foundation, I. V. Michurin consistently, step by step, built his theory of sexual hybridization. This theory refutes the main provisions of supporters of formal genetic science, who assert the independence of the heredity of organisms from their living conditions and propagandize “Mendel’s notorious pea laws,” the use of which in the selection of perennial crops, as Ivan Vladimirovich wrote, is not worth even dreaming of. He sharply condemned those who worked according to the principle: “Rash, mix, chat, maybe something else will come out.” In contrast, I. V. Michurin’s motto reads: “We cannot expect favors from nature: taking them from her is our task.”
Objecting to the views on heredity expressed by supporters of formal genetic “science,” he more than once argued that when the same initial parent pairs are repeatedly crossed, their successive offspring will never produce the same number of hybrids, in which strictly defined characteristics would always dominate father or mother according to Mendelian law 3:1. In all cases of crossing the same parental pairs, the resulting plants are not identical in their morphological and biological characteristics, because the inheritance of parental characteristics depends both on the selection of crossed varieties and on many other reasons.
Correct selection parental pairs is impossible without knowledge of the biological laws of inheritance by hybrid offspring of the characteristics and properties of the parents and the presence of deep relationships between the emerging nature of plant organisms and the conditions of their upbringing, established by I. V. Michurin, T. D. Lysenko and their followers.
1. In order to obtain a new variety with the desired qualities, it is necessary first of all to select for crossing those plants that have economically valuable traits that correspond to the breeding task.
I.V: Michurin has repeatedly emphasized the idea that modern breeders, as a rule, have no need to go through again the path traveled before them; Due to the presence of heredity in organisms, they must benefit from the results of the work of many generations of their predecessors.
Luther Burbank also pursued the same idea in his writings. He figuratively compared the choice of plants to cross with the work of an architect. Just as an architect selects building materials that correspond to the ideological concept of the future building, so a breeder plans for crossing plant forms, possessing the characteristics that he wants to see in the future variety. At the same time, the breeder has at his disposal an incomparably richer and more varied material that he can use to implement his plan than the amount of minerals or wood species known to the architect.
When developing new varieties, as T. D. Lysenko points out, it is very important to select the initial forms according to the principle of having the least amount of negative qualities, which could limit, under these specific conditions, development in the offspring best features and properties of parents.
2. I. V. Michurin attached important varietal and individual history of maternal and paternal plants, since knowledge of it allows us to foresee the possible nature of inheritance of the characteristics of parental forms by hybrid offspring.
“The most energetic ability to transmit their properties,” Ivan Vladimirovich pointed out, “is possessed, firstly, by all plants of pure species growing in the wild; secondly, all old cultivated varieties of plants are distinguished by greater energy, and the weakest in this regard need count recently bred young varieties fruit trees And berry bushes» *.

* I. V. Michurin, Selected Works, 1948, p. 69.

The dominance of the characteristics of wild plants when they are crossed with cultivated ones is due to the presence of much more conservative heredity in them than in the cultural forms that were later formed in the process of human activity.
Even Charles Darwin noted that in plants and animals common in natural conditions, such sharp and sudden changes are not observed as are known in domesticated animals and cultivated plants. It must be assumed that the very fact of cultivation, i.e. the movement of plants from natural conditions to new - artificial ones, and their cultivation for many generations under the influence of certain methods of agricultural technology and phytotechnics contributes to the formation of a more plastic heredity in them and a more active reaction to change. conditions environment than in wild forms.
3. To obtain hybrid offspring with plastic heredity, capable of being most amenable to directed education and providing the richest variety of forms for subsequent selection, I. V. Michurin recommended using geographically and genetically distant crossing.
As a rule, during distant (interspecific or intergeneric) hybridization, the resulting hybrid offspring relatively easily adapts to the living conditions that are provided to it.
On the big practical material I.V. Michurin proved the possibility of crossing distantly related forms of plants and widely used distant hybridization in his practical work in breeding famous varieties: apple trees - Bellefleur-Chinese, Kandil-Chinese (hybrids between domestic and Chinese apple trees), Bellefleur red, Bellefleur record (hybrids between domestic apple tree and Nedzvetsky apple tree), Taiga (hybrid between Kandil-Chinese and Siberian apple); pears - Bere winter Michurina, Tolstobezhka, Rakovka (hybrids between the common cultivated pear and the Ussuri pear); cherries - Beauty of the North, Bastard of cherries (cherry-cherry hybrids); new plants - cerapadus (hybrids of steppe cherry with Japanese bird cherry); plums - Transparent yellow (hybrid of plum with apricot), Rencloud blackthorn, Sweet sloe (hybrids of plum with wild thorn); grapes - Russian Concord, Metallic, Buitur (hybrids between American and Amur species), Korinka Michurina (hybrid between Amur and cultivated grape species). Its varieties are also known - hybrids of rowan with medlar, rowan with hawthorn, raspberry with blackberry, etc.
The method of distant hybridization has found wide application in the work of Soviet breeders, as it opens up great opportunities for obtaining new forms of useful plants.
Plants that are distant in relationship may also be distant in geographical origin and according to the environmental conditions in which each of them was formed.
It is advisable to carry out crossing geographically distant plants and raising their hybrid offspring in new natural conditions, alien to both maternal and paternal parents. In this case, according to Michurin’s teaching, those conditions that are necessary for a strong manifestation of the characteristics of the closest ancestors in the offspring are excluded. Classic example practical use This situation can be supported by I.V. Michurin’s receipt of a new high-quality winter pear variety, Bere winter Michurina, in the conditions of the Tambov region.
For a long time he was unable to obtain a new variety of pear with the fruits of good taste qualities, suitable for long-term winter storage. To this end, he carried out numerous crosses of high-quality Western European winter varieties pears (Bere Dil, Bere Clerzho, Bere Ligelya, Saint-Germain) with local varieties (Tonkovetka, Tsarskaya, Bessemyanka). However, the grown seedlings did not have the desired property due to the dominance of early fruit ripening in the offspring, characteristic of local pear varieties. Only by crossing Italian variety Bere Royal pears with a young, first-blooming seedling of the Ussuri pear (the birthplace of this type of pear is Far East) he obtained hybrids with fruits of summer, autumn and winter ripening. One of them turned out to be especially valuable, since it inherited the best properties of both parents - the frost resistance inherent in the Ussuri pear, the size of the fruit, their wonderful dessert taste, as well as the ability to long-term storage in fresh form, characteristic of the Bere royal variety.
4. Based on many years of experiments and observations, I. V. Michurin discovered another important pattern: in the process of crossing varieties that are equivalent in the sense of conservatism of heredity, the maternal organism, being a natural mentor, as a rule, more fully transmits its characteristics and properties to the offspring than the paternal one .
Guided by this pattern, Soviet breeders When carrying out crosses, in the role of the maternal parent, the plant is often selected whose economically valuable traits and properties are desirable to be seen in the offspring. If there is a need to weaken the individual strength of the hereditary transmission of the maternal parent, then it is necessary to select a young seedling, flowering for the first time, with heredity already shaken by preliminary hybridization, as the mother.
5. Ivan Vladimirovich Michurin is the first breeder to use a mixture of pollen of different varieties for crossing. True, he used the pollen mixture method, mainly in order to overcome non-crossability during the hybridization of plants that were distant in relationship, but his followers proved the advisability of using a pollen mixture of a number of varieties in ordinary crossings.
Darwin also noted that crossing individuals who were exposed to various conditions during the life of previous generations has a beneficial effect on the offspring, since in this case their germ cells are differentiated to one degree or another. When flowers self-pollinate, such differentiation of sexual elements is not observed, so its effect on the offspring is unfavorable.
This observation served as the basis for another important conclusion of Charles Darwin about the presence of obligatory selectivity of plant sexual elements in natural conditions. I. V. Michurin and T. D. Lysenko developed Darwin’s thesis about the presence of selectivity in plant fertilization and proved that the inheritance of parental characteristics by offspring during artificial hybridization is highly dependent on the selective nature of the fertilization process, and this dependence is of a dual nature.
Not every pollen grain biologically corresponds to a specific egg, therefore, the more pollen grains of different varieties are applied during pollination on the stigma of a castrated flower, the more great opportunity It is left to the mother plant to choose the most acceptable of them. Numerous experiments by the Michurinites have proven that in the presence of large selection Fertilization of pollen by flowers occurs more actively, the set seeds turn out to be much more viable and richer in nutrients, and the plants grown from them are more productive.
In addition, when pollinated with a mixture of pollen, as a result of the interaction of pollen grains of different varieties, a qualitatively new physiological environment is created, more favorable than with conventional pollination.
I.V. Michurin drew the attention of breeders to the other side of this process. It is not always the case that with artificial hybridization one should expect to obtain relatively more viable offspring. After all, biologically incompatible plants are often used as parents, the crossing of which is forced. For example, distant hybridization sometimes produces plants that are incapable of building even the most vital organs. However, T.D. Lysenko emphasizes that the selective ability of plants must be used to obtain sharp changes in heredity through forced crossing with those individuals whose pollen would not be selected by the maternal organism under natural conditions.
In this area, Michurin's agrobiological science puts forward new, not yet resolved problems that are of important theoretical significance.
For practical breeding work, the pollen mixture for crossing is selected according to the same principles noted earlier, i.e., the selection task, the economically valuable qualities of the parent varieties (including several paternal varieties), their biological characteristics and history of origin are taken into account.
6. It is not always possible for a breeder to obtain hybrid offspring with the desired characteristics by means of a single crossing of parental pairs pre-selected taking into account the indicated patterns of dominance of heredity. To achieve your goal, it is sometimes useful to resort to re-crossing the best of the resulting hybrid plants with one of the parents or with some other variety that has the desired qualities.
Attaching exceptional importance to the re-crossing of the first hybrid generation fruit crops received in middle lane Russia, with southern varieties, I.V. Michurin persistently pointed out to breeders: “Further, the third method should be considered the most essential in the development of new varieties of fruit plants - the method of re-crossing hybrids with the best cultivated (and foreign) varieties... Here we in most cases we will get a significant overall improvement both from the influence of the variety introduced into crossing with new ones good properties, and from the easier susceptibility of the hybrid at its young age and, moreover, still rooted” *.

* I. V. Michurin, Soch., vol. 1, 1948, pp. 496-498.

At the same time, he warned against using seedlings of the second or even third generation from natural pollination in harsh climatic conditions, because the new forms obtained in this way deviate mainly for the worse due to repeated negative influence local environmental factors on the dominance of parental traits.
The patterns of dominance of plant heredity established by I.V. Michurin, T.D. Lysenko and their students also apply to the culture of grapevines.
Long-term research carried out by the Department of Selection and Variety Study of the Ukrainian Research Institute of Viticulture and Winemaking named after. Tairov (P.K. Ayvazyan) established that in the first and second seed offspring of sexual hybrids there is a rather complex pattern of inheritance of the characteristics of the parents. In some seedlings, the traits of one parent may predominate, in others - of the other, in others - intermediate inheritance of traits may occur, and, finally, there are known cases when completely new traits and properties appear in the hybrid offspring that were completely absent in the original parental pairs.
As a rule, the most constant in terms of heredity are the wild-growing forms of pure species: Vitis Riparia, Vitis Rupestris, Vitis Labrusca, Vitis Amurenzis, etc., therefore, during interspecific hybridization of grapes, the seedlings of the first offspring obtained from crossing cultivated grapes with American wild species and rootstocks and grown in conventional agrotechnical conditions, predominantly inherit the characteristics of wild parents. Wherein most of plants, evading morphological characteristics towards wild forms, inherits from the mother plants (European varieties) instability to mildew and low frost resistance, and from the father varieties (wild forms) - low harvest quality. Seedlings that are similar in morphological characteristics to cultivated varieties are inferior in harvest quality to the mother cultivated variety.
A small number of interspecific hybrids with practical resistance to mildew and frost are close to wild species in their morphological characteristics (shoots and leaves), as well as in the quantity and quality of the harvest. Such seedlings are of interest for repeated and vegetative hybridization.
Research has also shown that during interspecific hybridization, it is best to take ancient indigenous grape varieties with good harvest quality as mother plants. Such varieties, formed in local conditions and having more stable heredity, more easily transmit their characteristics and properties to hybrid offspring than introduced ones.
In the hybrid offspring obtained from repeated crossings of interspecific hybrids with high-quality varieties, as one would expect, Substantial part seedlings are wild forms. In this case, too, the production of a large number of seedlings deviating in their characteristics from cultivated plants can be explained by the fact that wild varieties took part in the origin of one of the parents, which, due to their long existence, are distinguished by their exceptional ability to preserve their hereditary properties.
Within the same hybrid combination, under the same environmental conditions, the variety more fully transmits its characteristics and properties to the offspring (yield, vigor of bushes, size of bunches and berries, color of berries and juice, quality of the harvest, plant resistance to adverse conditions, etc.) in the event that it is taken as a mother plant. By providing the hybrid embryo at its youngest age, starting from the moment of formation of the zygote, with the necessary nutrients, the maternal body as a mentor accordingly influences the formation of the heredity of the offspring.
The correct selection of initial parent varieties for crossing is only the first stage breeding work, ending with the production of hybrid seeds. The subsequent process of formation of the heredity of seedlings is a very complex biological phenomenon, occurring under the influence of environmental conditions and often accompanied by the manifestation of a number of profound changes in them.

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In Goethe's times, as Goethe himself recalled, in Carlsbad - don't look on the map, now it's Karlovy Vary - vacationers on the waters liked to identify plants in bouquets according to Linnaeus. These bouquets were delivered daily to those drinking mineral waters in the shade of the colonnade (bicarbonate-sulfate-chloride-sodium - for the information of those gathering in Karlovy Vary) by a young handsome gardener, arousing increased interest among pale, lonely ladies.

The correct identification of each plant was a matter of honor and success for the gardener, who encouraged innocent botanical hobbies for a modest fee. It is difficult to say why - whether because of jealousy towards the gardener, or towards Linnaeus, but the poet severely disagreed with Linnaeus on the principles of plant taxonomy. Linnaeus, as is known, looked for differences in plants, but Goethe began to look for what was common and with this, it must be said, took the first step towards the genetic systematization of plants.

Women's passion for botany was understandable: Linnaeus' system was amazingly simple and understandable. This is not Stankov-Taliev’s “Identifier of Higher Plants of the European Part of the USSR”, more than a thousand pages long, which leads students to a pre-infarction state.

Linnaeus, who had never liked arithmetic, nevertheless laid it, one might say, as the basis of his system. He divided plants into 24 classes, of which 13 were distinguished by the number of stamens. Plants with one stamen in each flower are placed in the first class, with two - in the second, and so on until the tenth class, which includes plants with ten stamens. The 11th class included plants with 11-20 stamens; 20 or more stamens in a flower indicated that they belonged to the 12th and 13th classes. These two classes were distinguished by the level of location of the base of the stamens relative to the place of attachment of the pistil. Plants of classes 14 and 15 have stamens of unequal length. In flowers of classes 15-20, the stamens of plants are fused with each other or with the pistil. Class 21 included monoecious plants, which have partly staminate and partly fertile (pistillate) flowers. Class 22 includes dioecious plants, which develop only staminate flowers on some plants, and only fertile flowers on others. Class 23 included plants with a chaotic scattering of male and female flowers (including sometimes joint flowers) on the plant. In the 24th class, “secret” plants were united - all flowerless plants, from ferns to algae. The latter were called “cryptogamy” for the reason that botanists did not know how they reproduce. It is now that biologists know their organization and reproduction better than flowering plants.

Linnaeus classified 20 of the 23 classes as glaucous bisexual flowers. It was these that he considered the rule in the plant kingdom, the rest - a curious exception. It seems logical, it’s more convenient for plants - the stamens and pistils are nearby, which means the marriage goes without a hitch; the result of love - the fruit and seed appear as a result of self-pollination, encrypted by biologists with the Latin word autogamia.

After Linnaeus, it became clear that some plants only have seemingly bisexual flowers. Although they have stamens and pistils nearby in the flowers, the pollen cells in the anthers are underdeveloped and the whole plant looks like a eunuch - it’s disgusting to watch. Other flowers cannot fertilize themselves, but their pollen is capable of producing offspring when pollinating the pistils of foreign plants.

Since botanists have long been accustomed to call everything by Latin names, they called the collection of stamens of a flower androecium, and the collection of pistils (or simply pistil) - gynoecium. But since no scientist will ever stop at what has already been achieved, botanists subsequently, depending on the structure of the flowers, divided them into bisexual (containing an androecium and gynoecium) and unisexual (containing either an androecium or gynoecium). If male and female flowers bloom on the same plant, it is called monoecious (corn), but if on different ones, it is called dioecious (hemp). Polygamous species have bisexual and unisexual flowers on one plant (melon, sunflower). However, apparently, in defiance of botanical scientists, nature sometimes exposes to their inquisitive eye all forms of transition from one sexual type of flower and plant to another, even barren flowers, completely devoid of stamens and with underdeveloped pistils.

The weed plant chickweed, or stomper, which is extremely annoying to gardeners, has ten stamens in two five-membered whorls, of which usually 5 internal ones, with some addition of those from the outer whorl, are wrinkled and devoid of pollen. The flower heads of the burnet (Poterium polygamum) contain, in addition to purely fertile and purely staminate flowers, also true bisexual flowers. They represent all the examples of the transition from true bisexual to purely maternal type flowers. By the way, this botanical genus is exceptional among Rosaceae for its tendency to wind pollination.

The degrees of separation among pseudobisexual fertile and staminate flowers are also unusually varied. Thistle, asparagus, persimmon, grapes, some scabioses, saxifrage, and valerian have flowers that seem to be bisexual at first glance. They have well-developed pistils and visible stamens, the anthers of which may or may not contain pollen. In the latter case, these are pseudobisexual flowers. What to do, “false Dmitry” is found in nature. The same can be said about part of the flowers in the racemes of horse chestnuts and some types of sorrel, as well as in the flowers in the center of the coltsfoot baskets and marigolds, which have the appearance of true bisexual flowers, but whose ovaries do not produce viable seeds, since the stigma unable to pass pollen tubes through itself.

In the brushes of sycamore (one of the types of maple) you can see everything possible transitions from pseudobisexual staminate flowers with well-developed large ovaries to those in which the pistils are underdeveloped or completely absent. Transitions from true bisexual flowers to barren flowers can be found in several species of steppe hyacinth.

Three-domed species are also known: some plants bear only male flowers, others only female ones, and still others bear bisexual flowers (resinous flowers). Among the oddities of plants, one can note the change in sex with age or in certain years. The grape is heart-shaped, classified as typically dioecious in its homeland, in Vienna botanical garden represented by bushes with staminate flowers. But in some years, vine bushes confuse tour guides because, in addition to staminate ones, they produce true bisexual flowers.

In many plants, self-fertilization is prevented by the non-simultaneous maturation of stamens and pistils in a flower - dichogamy (sunflower, raspberry, pear, apple, plum), in which a distinction is made between proterandry, when the stamens mature before the pistils mature, and protogyny, when the pistils mature before the stamens.

Mainly proterandric are Asteraceae, Lamiaceae, Malvaceae, Cloveaceae and Legumes; The following are proterogynic: rushes and ozhikas, kirkazonaceae and daphniaceae, honeysuckles, globulariaceae, nightshades, rosaceae and cruciferous plants. All monoecious plants are proterogynous: sedges, cattails, urchins, aroids with monoecious flowers, corn, monoecious stinging nettle, urut, burnet, cocklebur, mad cucumber, euphorbia plants, alder, birch, walnut, plane tree, elm, oak, hazel, beech . In the trees and shrubs mentioned here, the anthers begin to shed dust with a delay of 2-3 days. For alpine green alder this difference is 4-5 days, and for small cattail it is even nine.

For the most part, dioecious plants are proterogynic. In large willow thickets along the banks of our rivers, which are not poisoned by chemicals, some species are still represented by numerous shrubs. Some of them bear staminate flowers, others - pistillate flowers. They are practically in the same conditions, but, despite the same external conditions in the same area, bushes with pistillate flowers always deftly outstrip their “men” with staminate flowers in flowering. In belotal, purple vine, basket willow and willow, the stigmas in their maturation are 2-3 days ahead of the opening of the staminate flowers. It’s the same with alpine willows - check it out if you happen to visit the Alps. But here the time difference is limited to only one day, from which it is reasonable to conclude that our willows are the most proterogynous willows in the world.

In hemp plants growing nearby, at the beginning of flowering you can notice stigmas, ready to receive pollen, although not a single staminate flower has yet opened - they will open only after 4-5 days. In the woodleaf, or hen, growing in deciduous forests and shrubs, maternal and paternal individuals are located nearby. Nevertheless, their pistillate flowers open two days before their staminate flowers. The same is true for hops and many other dioecious plants.

In a few plants, self-fertilization is difficult because the stamens and pistils are arranged in such a way that it is difficult for pollen to reach the stigma of its flower. For example, with heterostyly, some individuals have flowers with long pistils and short stamens, while others have the opposite. Heterostylous (variably columnar) include some gentians (for example, watch, or trefoil), buckwheat, different kinds Lenza, numerous primroses (for example, breaker, turcha, primrose, or primrose), as well as many borage (forget-me-nots, lungwort, etc.).

Vakhta has very elegant shaggy white-pink star-shaped flowers, collected in a brush on a leafless stem. Some flowers have a low style and an anther attached above it, while others, on the contrary, have high styles and anthers attached underneath. The stigmas of the plant mature before the stamens. Insects visiting watch flowers touch either the pistils or the stamens with the same part of their body, carrying out strictly cross-pollination. However, during prolonged bad weather, the flower is closed and forced to self-fertilize.

Primrose, better known to children as rams, is one of the first spring flowers to bloom. Hence the Latin name primus - first. Only bumblebees and butterflies pollinate the plant. Due to the difference in columnarity, the pistils of some flowers can only be pollinated by pollen from other flowers. If a bumblebee lands on a flower with a low pistil, its head touches the high-standing stamens. Flying to a flower with a high pistil, it touches the stigma with its head and produces cross-pollination.

The phenomenon of heterocolumnarity was first discovered on the flowers of the bog grass, and then on other plants. Turchi's superiority in this regard seems even incredible, considering that the entire plant is immersed in water, and only in July do flowers appear above the water. Another remarkable thing about turkish grass is that it has no roots, and its suction functions are performed by the cells of the skin of the leaves.

In buckwheat, according to the sworn assurance of geneticists, long columnarity is controlled by the recessive allele s, and short columnarity by the dominant allele S (we remind you that an allele is one of the forms of the state of the same gene). Since pollination does not occur within one type of flower, an equal ratio of plants with genotypes Ss and ss is always maintained in populations; this can be seen from the Punnett lattice, known from a school biology course:

that is, a 1:1 split, as in humans, into boys (AT) and girls (XX) in the offspring.

According to the structure of the flower, buckwheat is adapted to cross-pollination mainly by insects (flies, bumblebees and especially bees), which are attracted by nectar, and only partly by the wind. During normal (legitimate) pollination, when the pollen of short stamens falls on the stigmas of short styles and, accordingly, the pollen of long stamens - on the stigmas of long styles, the greatest number seeds

Weeping grass (Lythrum salicaria) is one of our most interesting plants. The fact is that weeping grass flowers have pistils of three various sizes and 12 stamens, equally spaced in two circles. In some flowers the pistil is above both circles of stamens, in others it is between them and in others it is below both circles. Consequently, the stamens are located at different heights in the same way as the pistils, allowing for cross-pollination. An insect, flying in for nectar, smears itself with pollen and deposits it on the stigma of the pistil, which is the same length as the stamen from which the pollen was removed. Fertilization occurs normally when pollen is transferred from a stamen that is the same length as the pistil. Pollen grains from stamens of three different heights differ from each other in size and partly in color, and accordingly, the length of the papillae on the stigmas of three different heights is also different, because the stigmas must catch different pollen. The pollination process was first studied in detail by Charles Darwin.

In some plants, the stamens and pistils are arranged in strict order, presenting themselves to insects for “unloading” pollen or “loading” stigma. In our common rue, found on the slopes and hills in the forests of the Southern Crimea, the flower contains ten anthers supported by straight, star-shaped threads. First, one filament rises, placing the anther it supports in the middle of the flower along a line leading to the nectar, which is secreted by a fleshy ring at the base of the pistil. She maintains this position for about a day, then returns to her previous position. While the first stamen bends, another one rises - and everything repeats. This continues until all ten anthers, one after the other, stand in the middle of the flower. When, finally, the tenth stamen bends back, the stigma appears in the center of the flower, which at this time has become receptive to pollination.

In the bisexual flowers of the nettle family, the stigma develops even before the flower opens and is the first to protrude from the greenish bud of the flower. The anthers on bent legs, as if on springs, are covered with interlocking small greenish integumentary leaves. But before they allow the anthers to rise from their “knees”, straighten up and scatter their pollen in the form of a cloud in the air, the stigma withers and the style is separated along with the stigma from the ovary. So by the time the pollen is released from the anthers, the ovary ends in a point - the dried base of the fallen style.

Usually in plants this all happens differently: first, the anthers and stamens fall off in the flower, and only after that the stigma acquires the ability to receive pollen. In balsam flowers, the anthers are fused together and form something like a cap over the stigma. After the flower has opened and made itself accessible to flying insects, the anthers immediately crack, and a cap formed by the opened anthers appears before us. But then the threads of the stamens separate, and the cap falls out of the flower. Only now do the stigmas appear, fully ripe. The same can be observed in large-flowered species of crane grass and geranium.

In the bisexual flowers of Tradescantia, bred at home and misunderstoodly called “woman's gossip,” the anthers open a little earlier than the stigmas become receptive to pollen. But as soon as the stigma is ready for pollination, the stamens curl into a spiral, and soon after this the integumentary leaves fade, covering the anthers on curled threads. The style protrudes, and the stigmas are receptive to pollen throughout the next day. These flowers are visited by insects with short proboscis to feast on the juice of the crushed integumentary leaves that hide the stamens, while they touch the stigmas and pollinate them with pollen brought from other flowers. Pollination of one's anthers by pollen is no longer possible.

Dichogamy botanists, who rely in their research only on morphoecological differences, without taking into account the content of genomes, are obliged to the abundance of sedge species, endlessly rediscovered, and even rediscovered. Moreover, the so-called “species” of sedges easily interbreed with each other, producing many intermediate forms that are readily accepted as new “species” (the authors of the species are attracted by the opportunity to immortalize their name in Latin transcription). Imperfect (incomplete) dichogamy in botanical genera with monoecious flowers ensures, for example, in sedges, first the so-called interspecific, and later intraspecific crossing. This is understandable, since the stigma of the very first flowering plant of a proterogynic species can only be pollinated by the pollen of other “species” that flowered even earlier.

Lysenko believed that “dialectical materialism, developed and raised to a new height by the works of Comrade Stalin, for Soviet biologists, for the Michurinists, is the most valuable, most powerful theoretical weapon in solving deep questions of biology, including the question of the origin of some species from others.” . That is why he gave a super-dialectical definition of species at this new height: “A species is a special, qualitatively defined state of living forms of matter. Essential characteristic feature species of plants, animals and microorganisms are certain intraspecific relationships between individuals.” That's it.

Not all botanists want to see that in the dialectical unity of form and content, content is decisive. The content of a species is the unity of the genetic structure of the populations that make it up. Outwardly, it manifests itself in phenotypic similarity, free interbreeding, especially in the ability to produce fertile offspring when crossed. Hereditary information is what qualitatively determines the species and constitutes its content. It is difficult to say whether life arose simultaneously with heredity (I suspect that it did), but one thing is certain: with the advent of discrete heredity, species appeared on the globe.

Taking into account the formulations known to science, the definition of a species can be as follows: species - a qualitatively isolated at a given stage of the evolutionary process, a complex and mobile community of organisms, characterized by unity of origin, common genetic constitution, hereditary stability and fertility of offspring. Most of the identified “species” of sedges and willows do not correspond to this definition.

When identifying “good” or true species based on crossability and the formation of fertile offspring, one must not forget about the phenomenon of self-incompatibility - the impossibility of self-fertilization in some hermaphroditic organisms or cross-fertilization between individuals of a species with the same genetic factors of incompatibility. The main function of self-incompatibility systems is to prevent self-fertilization and promote interbreeding between unrelated individuals.

There are gametophytic, sporophytic and heteromorphic self-incompatibility. Gametophytic self-incompatibility is the most common (cereals, beets, alfalfa, fruits, potatoes, etc.). This system is characterized by the independent action in pollen and style of two alleles of the S. incompatibility locus present in each individual. For example, pollen from a plant with the genotype S 1 S 2 behaves as S 1 or S 2 depending on which allele the pollen grain contains. None of the alleles exhibit dominance or any other form of inter-allelic interaction. The same complete independence of action is observed in the column.

The incompatibility reaction manifests itself in the pistil style: the growth of pollen tubes carrying a given allele stops in the styles containing the identical allele. If all alleles involved in hybridization are different, for example S 1 S 2 XS 3 S 4, then all pollen tubes are compatible, the ovary is normal and 4 cross-compatible genotypes are formed in the offspring. In the vast majority of species studied, gametophytic incompatibility is controlled by one or two loci.

Sporophytic incompatibility was first described in guayule. In sporophytic self-incompatibility, the behavior of each pollen grain depends on the genotype of the style. Thus, if S 1 is dominant over S 2 , all pollen from plant S 1 S 2 will react as S 1 and will be able to penetrate into styles carrying the S 2 allele, regardless of the genotype of the pollen tube - S 1 or S 2 .

Heteromorphic incompatibility arises on the basis of heterostyly, which we have already described earlier.

One of the plant's adaptations for cross-fertilization is male sterility. In recent decades, male sterility in cultivated plants has aroused great interest among breeders and seed growers, as it makes it possible to obtain first-generation heterotic hybrids on a large scale, which give yield increases of up to 40 percent compared to conventional varieties, are characterized by early and uniform ripening, high uniformity and resistance to adverse environmental factors.

To date, cytoplasmic male sterility (CMS) and genetic male sterility (GMS), controlled by genes in the cell nucleus, have been described. Cytoplasmic male sterility in plants is caused by the interaction of sterile cytoplasm (S) with 1-3 pairs of recessive nuclear genes (rf). In the presence of dominant nuclear (RF) genes, pollen fertility is restored. CMS is widely used to produce heterotic hybrids in industrial scale in corn, sorghum, sugar beets, onions, carrots. Usually,

To use CMS in seed production of first generation hybrids (they are designated F 1), fertile sterility fixers with the Nrfrf genotype (N - normal cytoplasm), their sterile analogues - Srfrf and fertility restorers - RfRf are used.

Genetic male sterility is used to obtain heterotic seeds in tomatoes, peppers, and barley. When producing hybrid seeds based on one recessive GMS gene, splitting in Fi occurs according to Mendel in the ratio of 3 fertile: 1 sterile plant, since, unlike CMS, male sterility is transmitted through both female and male gametes.

Crossings, as is known, are widely used in plant breeding and seed production. The possibility of artificially producing hybrids was first suggested by the German scientist R. Camerarius in 1694, and, as often happens, no one believed him. Only in 1760, a German botanist and honorary member Petersburg Academy of Sciences Joseph Kölreuther received a hybrid of Peruvian paniculata tobacco with shag. From this year, scientists begin conscious hybridization.

Depending on the degree of relatedness of the crossed forms, intraspecific and distant - interspecific and intergeneric hybridization are distinguished. If two parental forms are involved in the crossing, we speak of simple, or pair, hybridization, if more than two - of complex. There are direct (A×B) and reverse (B×A) crosses, which are generally called reciprocal. Crossing hybrids with one of the parents, for example (A×B)×A or (A×B)×B, is called backcross, or return.

To designate hybrids and parental forms, the following symbols are used: P - parental form; F 1 - first generation hybrid; F 2 - second, etc.; B 1, or BC 1, is the first generation of backcross; B 2, or BC 2 - second, etc. The maternal form is indicated by the symbol ♀, the paternal form by ♂. However, most often they do without the latter, placing the maternal form in the first place in the records of crossing combinations, and the paternal form in second.

The method and technique of crossing depend on the biology of flowering and pollination, fertilization, the structural features of flowers (bisexual, dioecious), the location of the latter on the plant and in the inflorescence, the method of pollination, the duration of the viability of the pistil and pollen, and the conditions of crossing.

Breeders use forced, limited-free and free crossings, which often require castration of plants. Castration consists of removing immature anthers or damaging them by pruning, thermal sterilization (hot air or water) or chemical castration - the use of specially selected gametocides.

In forced crossing, castrated and isolated mother plants are pollinated with pollen from the father plant. In free crossing, the parent forms are sown in alternating rows. Castrated, male-sterile or biologically female mother plants are pollinated by pollen from nearby father plants.

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Types of crossing

In breeding practice, two types of crossing are used:

–simple (one-time)– two varieties are crossed with each other (A X B)

Variations:

Simple doubles

Reciprocal

Multiple

Topcrosses

Diallelic

–complex (multiple)– three grades or more [(A x B) x C] x D

Variations:

Returnable (bkcrosses)

Convergent

Stepped

Interhybrid

Simple crosses

Selection is carried out directly in hybrid offspring.

Based on simple paired crosses, work with hybrid material is reduced to the selection of hybrid plants in splitting generations and the evaluation of their offspring.

This type of crossing has great importance with intervarietal hybridization than with interspecific hybridization, when a single crossing is not enough to obtain the required combination of characteristics in a hybrid.

Reciprocal crosses

Reciprocal (direct and back crossing, the parent form is swapped) –

each of the two parent components is used in one case as the maternal form, and in the second case as the paternal form.

This type of crossing is especially important for distant hybridization, when in direct and reverse combinations the results can be different both in seed set and in the quality of the hybrid.

Required to check the presence of genetic material in the cytoplasm of parental forms. Nuclear material is transferred equally during forward and reverse crossing; the cytoplasm is transmitted to hybrids only through the maternal line. With reciprocal crosses, in some cases the influence of the cytoplasm of the maternal form can be significant, in others it may not appear at all.

11. Complex stepwise and interhybrid crosses.

Step crossings

During stepwise hybridization, the resulting hybrid plants are re-crossed with a third variety, and if necessary, then a fourth variety or species is also involved in the crossing, etc. Thus, several parental forms are involved in these crosses, which are sequentially (stepwise) included in the hybridization .

With stepwise crossings, hybrid material is created, including the germplasm of several varieties or even species of plants. By selecting, for example, a sequence of stepwise hybridization of a variety, one of which is early-ripening, the second is high-yielding, and the third is disease-resistant, one can expect to obtain a hybrid that combines all three of these properties.

Interhybrid crosses

To create source material with a large breadth of genetic variability, it is advisable to use the method of complex or interhybrid crossing.

Its essence lies in the fact that a population is created by crossing a large group of parental forms, and, as a rule, F1 individuals are crossed immediately.

For example, a crossbreeding scheme for 16 parent varieties will look like this:

1st year: (1x2); (3x4); (5x6); (7x8); (9x10); (11x12); (13x14); (15x16).

2nd year: (1x2)x(3x4); (5x6)x(7x8); (9x10)x(11x12); (13x14)x(15x16).

3rd year: [(1x2)x(3x4)]x[(5x6)x(7x8)]; [(9x10)x(11x12)]x[(13x14)x(15x16)].

4th year: ([(1x2)x(3x4)]x[(5x6)x(7x8)])x([(9x10)x(11x12)]x[(13x14)x(15x16)]).

Using this method, over four generations of crossing, the prerequisites are created for the formation of a recombined genotype, the genes of which can come from all 16 varieties or lines.

Option 1 - complex step crossing

A x B => F 1 (reseeding) => F 2 – select noticeable characteristics A and B, cross with variety C => F 1 (reseeding) => F 2 – select noticeable characteristics A, B, C, cross with D => F 1 (reseeding) => F 2 select ABSD (1 out of 256). It took 6 years.

Option 2 - interhybrid:

We sow A x B and C x D in parallel => cross them F 1 with each other => F 1 replant => F 2 select ABSD (1 out of 4096 is a huge job). It took 4 years.

The first option is almost always used.

CENTAURS IN THE PLANT WORLD

"Centaurs" in the plant world. Achievements of Russian, European and American scientists. How the plum and everyone's favorite strawberry appeared. Creation of new varieties of wheat. The main achievement of Russian scientists is cabbage radish.

The list of plant “centaurs” is not at all limited to cabbage-radish hybrids. Thus, as a result of crossing two grain crops - rye and wheat - scientists obtained a number of forms, united by the common name triticale. Triticale has good yield, winter hardiness and is resistant to many wheat diseases. Thanks to hybridization wheat and a malicious field weed - wheatgrass - breeders obtained valuable plant varieties - wheat-wheatgrass hybrids that are resistant to lodging and have high yields. Another famous Russian breeder, I.V. Michurin, crossed Pennsylvania cherry (a very frost-resistant species, unlike the usual cherry) with bird cherry and synthesized a new plant, which he called cerapadus. Only much later was it discovered that cerapaduses spontaneously arise in the Pamirs, but in a slightly different way.