Introduction. founder of the doctrine of plant immunity n. And. Vavilov, who initiated the study of its genetic nature, believed that plant resistance to pathogens. plant immunity. Basic theories Formation of immunity of plants, animals and humans

Extensive system Agriculture and unreasonable chemicalization greatly complicate the phytosanitary situation. Imperfect agricultural technology, monoculture, uncultivated weedy fields create exceptionally favorable conditions for the spread of infection and pests.

At all stages of ontogeny, plants interact with many other organisms, most of which are harmful. The cause of various diseases of plants and seeds can be mushrooms , bacteria And viruses .

Diseases are manifested as a result of the interaction of two organisms - a plant and a pathogen that destroys plant cells, releasing toxins in them, and digests them through depolymerase enzymes. The reverse reaction of plants consists in neutralizing toxins, inactivating depolymerases, and inhibiting the growth of pathogens through endogenous antibiotics.

The resistance of plants to pathogens is called immunity , or phytoimmunity . N. I. Vavilov singled out natural , or congenital , And acquired immunity. Depending on the mechanism of protective functions, immunity can be active And passive . Active, or physiological, immunity is determined by the active reaction of plant cells to the penetration of a pathogen into them. Passive immunity is a category of resistance, which is associated with the features of both the morphological and anatomical structure of plants.

The effectiveness of physiological immunity is mainly due to the weak development of the pathogen with a sharp manifestation of immunity - its early or late death, which is often accompanied by local death of the cells of the plant itself.

Immunity is completely dependent on the physiological reactions of the cytoplasm of the fungus and host cells. The specialization of phytopathogenic organisms is determined by the ability of their metabolites to suppress the activity of defense reactions induced in the plant by infection. If plant cells perceive an invading pathogen as a foreign organism, a series of biochemical changes occur to eliminate it, so infection does not occur. Otherwise, infection occurs.

The nature of the development of the disease depends on the characteristics of both components and conditions. environment. The presence of infection does not mean the manifestation of the disease. Scientist J. Deverall in this regard distinguishes two types of infection: 1) high if the pathogen is virulent and the plant is susceptible to the disease; 2) low, characterized by the virulent state of the pathogen and increased plant resistance to it. With low virulence and weak resistance, an intermediate type of infection is noted.

Depending on the degree of virulence of the pathogen and the resistance of the plant, the nature of the disease is not the same. Based on this, Van der Plank singles out vertical And horizontal plant resistance to diseases. Vertical stability observed in the case when the variety is more resistant to one races of the pathogen than to others. Horizontal resistance is manifested to all races of the pathogen in the same way.

The immunity of a plant to diseases is determined by its genotype and environmental conditions. NI Vavilov gives information that varieties of soft wheat are very affected by leaf rust, while forms of durum wheat are resistant to this disease. The founder of the doctrine of phytoimmunity came to the conclusion that hereditary differences in plant varieties in terms of immunity are constant and undergo little variability under the influence of environmental factors. Regarding physiological immunity, N. I. Vavilov believes that in this case heredity is stronger than the environment. However, giving preference to genotypic features, he does not deny the influence of exogenous factors on disease resistance. In this regard, the author points to three categories of immunity factors, or vice versa, susceptibility: 1) hereditary properties of the variety; 2) selective ability of the pathogen; 3) environmental conditions. As an example, data on negative impact increased soil acidity on plant resistance to certain fungal diseases.

A stronger infection of wheat with hard smut occurs at low temperatures (at 5 °C the infection was 70%, at 15 °C - 54%, at 30 °C - 1.7%). Moisture in the soil and air is often a factor initiating the development of rust, powdery mildew and other diseases. Susceptibility to fungal infection is also affected by light. If you keep oat plants in the dark and thereby reduce the intensity of photosynthesis and the formation of carbohydrates, then they become immune to rust infection. Plant resistance to disease is affected by fertilizers and other conditions..

The complexity of disease prevention and control is due to objective factors. It is very difficult to develop varieties that would remain resistant to the pathogen for a long time. Often, resistance is lost as a result of the emergence of new races and biotypes of pathogens against which the variety is not protected.

The fight against diseases is further complicated by the fact that pathogens adapt to chemicals protection.

The above factors are the main reason why the cost of plant protection in the conditions of modern agriculture is growing, outpacing the growth rate of agricultural production by 4–5 times. In the main grain-growing regions, the disease is often a limiting factor in obtaining high grain yields. In this regard, for the further intensification of agricultural production, new, advanced methods of plant protection are needed.

When developing new plant protection systems, it is necessary to focus on the regulation of the number harmful organisms in the agroecosystem. In the methodological plan, it is necessary to determine the complexes of harmful organisms that infect plants in different phases of development. It is necessary to create models that reflect the influence of certain types of pathogens and their complexes on crop formation and allow optimizing these processes through agrotechnological, organizational, economic and protective measures.

One of the most important prerequisites for obtaining seeds with high biological properties is the absence of pathogenic microflora. Diseases cause great harm to seeds at all stages of their life - during formation, storage and germination.

Through seeds, pathogens can be transmitted in three ways: 1) as mechanical impurities (sclerotia in rye seeds); 2) in the form of spores on the surface of seeds (hard smut of cereals); 3) in the form of mycelium in the middle of the seeds, for example, loose smut.

The microflora of seeds is divided into several groups. epiphytic microflora are microorganisms that inhabit the surface of seeds and feed on the waste products of plant cells. Under normal conditions, such pathogens do not invade inner fabric and do no significant harm Alternaria, Mucor, Dematium, Cladosporium and etc.). Endophytic (phytopathogenic) microflora consists of microorganisms that can penetrate into the internal parts of plants, develop there, cause disease in seeds and plants growing from them ( Fusarium, Helminthosporium, Septoria and etc.). Microorganisms that accidentally get on seeds by contact with contaminated surfaces of warehouse equipment, containers, soil particles, plant residues with dust and raindrops ( Рenісіllium, Aspergillus, Mucor and etc.). Storage mold, which develops as a result of the vital activity of fungi ( Рenісіllium, Aspergillus, Mucor and etc.).

Distinguish embryonic infection when pathogens are found in any of the constituent parts germ and extraembryonic infection when pathogens are found in the endosperm, sheath, pericarp and bracts. The placement of the pathogen in the seeds depends on the anatomy of the seeds and the site of entry specific to each microorganism.

N. I. Vavilov, the founder of the doctrine of plant immunity, who laid the foundation for the study of its genetic nature, believed that plant resistance to pathogens developed in the process of millennia of evolution in the centers of origin. If plants acquired resistance genes, pathogens could infect plants due to the emergence of new physiological races resulting from hybridization, mutation, heterokaryosis, and other processes. Within the population of a microorganism, shifts in the number of races are possible due to changes in varietal composition plants in a given region. The emergence of new races of the pathogen may be associated with the loss of resistance of a variety that was once resistant to this pathogen.

According to D. T. Strakhov, tissues resistant to plant diseases undergo regressive changes in pathogenic microorganisms associated with the action of plant enzymes and their metabolic reactions.

B. A. Rubin and his coworkers associated the reaction of plants aimed at inactivating the pathogen and its toxins with the activity of oxidative systems and energy metabolism of the cell. A variety of plant enzymes are characterized by different resistance to the waste products of pathogenic microorganisms. In immune forms of plants, the proportion of enzymes resistant to pathogen metabolites is higher than in non-immune forms. Oxidative systems (ceroxidases and polyphenol oxidases), as well as a number of flavone enzymes, are most resistant to metabolites.

In plants, as in invertebrates, the ability to produce antibodies in response to the appearance of antigens in the body has not been proven. Only vertebrates have special organs whose cells produce antibodies. In infected tissues of immune plants, functionally complete organelles are formed, which determine the ability of plant immune forms to increase the energy efficiency of respiration during infection. Respiratory failure caused by disease-causing agents is accompanied by the formation various connections, acting as a kind of chemical barrier that prevents the spread of infection.

The nature of plant responses to pest damage (the formation of chemical, mechanical, and growth barriers, the ability to regenerate damaged tissues, and replace lost organs) plays an important role in plant immunity to pests. Thus, a number of metabolites (alkaloids, glycosides, terpenes, saponins, etc.) have a toxic effect on the digestive apparatus, endocrine and other systems of insects and other plant pests.

In plant breeding for resistance to diseases and pests, hybridization (intraspecific, interspecific, and even intergeneric) is of great importance. On the basis of autopolyploids, hybrids between different chromosome species are obtained. Such polyploids were created, for example, by M.F. Ternovsky when breeding tobacco varieties resistant to powdery mildew. For creating resistant varieties artificial mutagenesis can be used, and in cross-pollinated plants, selection among heterozygous populations. So L. A. Zhdanov and V. S. Pustovoit obtained sunflower varieties resistant to broomrape.

For long-term preservation of the resistance of varieties, the following methods are proposed:

Creation of multiline varieties by crossing economically valuable forms with varieties carrying different resistance genes, due to which new races of pathogens cannot accumulate in the resulting hybrids;

Combination of R-genes with field resistance genes in one variety;

Periodic change of varietal composition on the farm, which leads to increased sustainability.

IN last years The development of crop production in our country was associated with a number of negative processes associated with pollution of the environment and crop production by xenobiotics, high economic and energy costs. The maximum use of the biological potential of agricultural crops can become one of the alternative ways of developing the agronomic sector of agricultural production. Certain hopes in this regard are associated with genetic engineering - a set of methodological approaches that make it possible to change the design of the plant genome by transferring foreign genes into it, which makes it possible to obtain new forms of plants, significantly expand the process of manipulating the plant genome and reduce the time spent on obtaining new agricultural varieties. cultures. Recently, methods of creating transgenic plants are beginning to be used to obtain plants resistant to viral, fungal and bacterial diseases, as well as to some pests (Colorado potato beetle, corn stem borer, cotton moth and cutworm, tobacco leaf roller, etc.). In terms of its methods and objects, this direction differs sharply from traditional breeding for plant immunity, but pursues the same goal - the creation of forms that are highly resistant to harmful organisms.

A brilliant substantiation of the role of resistant varieties in plant protection was given by N. I. Vavilov, who wrote that among the measures to protect plants from various diseases caused by parasitic fungi, bacteria, viruses, and various insects, the most radical means of control is the introduction of immune varieties into the culture or the creation of such by crossing. For cereals, which occupy three-quarters of the total area under crops, the replacement of susceptible varieties with resistant forms is, in fact, the most affordable way to combat infections such as rust, powdery mildew, loose smut of wheat, various fusariums, blotches.

Domestic and world experience in agriculture shows that plant protection should be based on complex (integrated) systems of measures, the basis of which is the presence of crop varieties resistant to diseases and pests.

In subsequent chapters, we will consider the main patterns that determine the presence of resistance traits in plants, the ways they effective use in the process of selection, ways to give plants induced immunity.

1. HISTORY OF THE ORIGIN AND DEVELOPMENT OF THE STUDY ON PLANT IMMUNITY.

Ideas about immunity began to take shape already in ancient times. According to historical records ancient india, China and Egypt, many centuries before our era, the population of the Earth suffered from epidemics. Observing their emergence and development, people came to the conclusion that not every person is susceptible to the effects of the disease and that one who has been ill with any of these terrible diseases does not fall ill with it again.

By the middle of the II century. BC e. the idea of ​​the uniqueness of human disease with such diseases as plague and others is becoming generally accepted. At the same time, those who had recovered from it began to be widely used to care for patients with plague. It is logical to assume that it is at this stage of development human society on the basis of data obtained by observing the spread of epidemiological diseases, immunology arose. From the very beginning of its development, it sought to use the collected observations for the practical protection of the population from infectious diseases. For many centuries, in order to protect people from smallpox, one way or another, deliberate infection with this disease was carried out, after which the body became immune to it. Thus, methods were developed to obtain immunity to this disease. However, with the widespread use of such methods, its main shortcomings were revealed, which consisted in the fact that many of the vaccinated smallpox proceeded in a severe form, often fatal. In addition, the vaccinated often became a source of infection and contributed to the maintenance of the smallpox epidemic. However, despite the obvious disadvantages, the method of deliberate infection clearly proved the possibility of artificially acquiring immunity by transferring the disease in a mild form.

Epochal significance in the development of immunity was the work of the English physician Edward Jenner (1798), in which he summarized the results of 25 years of observation and showed the possibility of cowpox vaccination in people and their acquisition of immunity to a similar human disease. These vaccinations are called vaccination (from Latin vaccinus - cow). Jenner's work was an outstanding achievement in practice, but without explaining the cause (etiology) of infectious diseases, it could not contribute to the further development of immunology. And only the classic works of Louis Pasteur (1879), which revealed the causes of infectious diseases, made it possible to take a fresh look at Jenner's results and appreciate them, which influenced both the subsequent development of immunology and the work of Pasteur himself, who proposed the use of weakened pathogens. for vaccination. Pasteur's discoveries laid the foundation for experimental immunology.

An outstanding contribution to the science of immunity was made by the Russian scientist I. I. Mechnikov (1845-1916). His works formed the basis of the theory of immunity. As the author of the phagocytic theory of protecting the body of animals and humans from pathogens, I. I. Mechnikov was awarded Nobel Prize. The essence of this theory lies in the fact that all animal organisms (from amoeba to humans inclusive) have the ability, with the help of special cells - phagocytes - to actively capture and digest microorganisms intracellularly. Using the circulatory system, phagocytes actively move inside living tissues and concentrate in places where microbes penetrate. It has now been established that animal organisms protect against microbes with the help of not only phagocytes, but also specific antibodies, interferon, etc.

A significant contribution to the development of immunology was made by the works of N. F. Gamaleya (1859-1949) and D. K. Zabolotny (1866-1929).

Despite the successful development of the theory of animal immunity, ideas about plant immunity developed extremely slowly. One of the founders of plant immunity was the Australian researcher Cobb, the author of the theory of the mechanical protection of plants from pathogens. The author attributed such features of the plant as a thickened cuticle, a peculiar structure of flowers, the ability to quickly form wound periderm at the site of injury, etc. to mechanical protective devices. Subsequently, this method of protection was called passive immunity. However, the mechanical theory could not exhaustively explain such a complex and diverse phenomenon as immunity.

Another theory of immunity, proposed by the Italian scientist Comes (1900), is based on the fact that plant immunity depends on the acidity of cell sap and the content of sugars in it. The higher the content of organic acids, tannins and anthocyanins in the cell sap of plants of one variety or another, the more resistant it is to diseases affecting it. Varieties that are high in sugars and relatively low in acids and tannins are more susceptible to disease. So, in grape varieties resistant to mildew and powdery mildew, acidity (% dry matter) is 6.2 ... 10.3, and in susceptible ones - from 0.5 ... 1.9. However, Comes' theory is not universal and cannot explain all cases of immunity. Thus, the study of many varieties of wheat and rye, which have different susceptibility to rust and smut, did not reveal a clear correlation between immunity and acid content in leaf tissues. Similar results were obtained for many other cultivated plants and their pathogens.

At the beginning of the XX century. new hypotheses appeared, the authors of which tried to explain the causes of plant immunity. Thus, the English researcher Massey proposed the chemotropic theory, according to which such plants have immunity, in which there are no substances necessary to attract parasites. Investigating the pathogens of cucumber and tomato, he showed that the juice of susceptible varieties contributed to the germination of pathogen spores, while the juice of resistant varieties inhibited this process. The chemotropic theory has been seriously criticized by a number of researchers. The most thorough criticism of this theory was given by N. I. Vavilov, who considered it unlikely that the cell sap contained in the vacuoles could remotely act on fungal hyphae and that some substances released from the tissues to the outside cannot be identified with the cell sap obtained by squeezing the substrates. on which the fungus was grown.

Protection of plants from diseases by creating and cultivating resistant varieties has been known since ancient times. Spontaneously carried out in places favorable for the development of pathogens of certain diseases, artificial selection on resistance to them has led to the creation of varieties of agricultural plants with increased resistance to these diseases. Natural disasters caused by the spread of especially dangerous diseases (grain rust, late blight of potatoes, oidium and mildew of grapes) stimulated the emergence of scientifically based plant breeding for immunity to diseases. In 1911, the 1st congress on selection was held, where A. A. Yachevsky (1863-1932) made a general report “On the importance of selection in the fight against fungal diseases of cultivated plants”. The data presented in the report indicated that successful work on the development of disease-resistant varieties is impossible without the development of a theory of plant immunity to infectious diseases.

In our country, the founder of the doctrine of plant immunity is N. I. Vavilov. His first works on plant immunity were published in 1913 and 1918, and the monograph "Plant Immunity to Infectious Diseases", published in 1919, was the first attempt to broadly generalize and theoretically substantiate all the material that had accumulated by that time in the field of the study of immunity. . In the same years, the works of N. I. Litvinov (1912) appeared on the assessment of the resistance of cereals to rust and E. N. Iretskaya (1912) on methods for selecting cereals for rust resistance. However, these works remained only episodes in the scientific activity of the authors.

N. I. Vavilov’s works “The doctrine of plant immunity to infectious diseases” (1935), reports at the I All-Union Conference on the fight against rust of cereals in 1937 and at the Biological Department of the USSR Academy of Sciences in 1940, a number of his articles and speeches at different times played a huge role in the development of theoretical ideas about the genetic characteristics of plants as decisive factors determining varietal and species resistance. N. I. Vavilov substantiated the proposition that the immunity of plants is inextricably linked with their genetic characteristics. Therefore, N. I. Vavilov considered the main task of breeding for resistance to be the search for species differences in plants on the basis of immunity. Collected by him and the VIR staff world collection varieties of cultivated plants is still a source of obtaining immune forms. Of great importance in the search for immune forms of plants is his concept of the parallel biological evolution of plants and their pathogens, which was later developed in the theory of the coupled evolution of parasites and their hosts, developed by P.M. Zhukovsky (1888-1975). The regularities of the manifestation of immunity, determined by the result of the interaction of the plant and the pathogen, N. I. Vavilov attributed to the field of physiological immunity.

The development of theoretical questions of the doctrine of plant immunity, begun by N. I. Vavilov, was continued in our country in subsequent years. Research was carried out in various directions, which was reflected in various explanations of the nature of plant immunity. Thus, the hypothesis of B. A. Rubin, based on the teachings of A. N. Bach, links plant resistance to infectious diseases with the activity of plant oxidative systems, mainly peroxidases, as well as a number of flavone enzymes. The activation of plant oxidative systems leads, on the one hand, to an increase in the energy efficiency of respiration, and, on the other hand, to disruption of its normal course, which is accompanied by the formation of various compounds that play the role of chemical barriers. E. A. Artsikhovskaya, V. A. Aksenova and others also participated in the development of this hypothesis.

Phytoncide theory, developed in 1928 by B.P. Tokin on the basis of the discovery of bactericidal substances in plants - phytoncides, was developed by D.D. Verderevsky (1904-1974), as well as employees of the Moldavian Plant Protection Station and the Chisinau Agricultural Institute (1944-1976 ).

In the 80s of the last century, L. V. Metlitsky, O. L. Ozeretskovskaya, and others developed a theory of immunity associated with the formation in plants of special substances - phytoalexins, which arise in response to infection by incompatible species or races of pathogens. They discovered a new potato phytoalexin - lyubin.

A number of interesting provisions of the theory of immunity were developed by K. T. Sukhorukoy, who worked in the Main Botanical Garden of the Academy of Sciences of the USSR, as well as a group of employees led by L. N. Andreev, engaged in the development of various aspects of the doctrine of plant immunity to rust diseases, peronosporosis and verticillium wilt.

In 1935 T.I. Fedotova (VIZR) discovered for the first time the affinity of host and pathogen proteins. All the previously listed hypotheses about the nature of plant immunity associated it with only one or a group of related protective properties plants. However, N. I. Vavilov emphasized that the nature of immunity is complex and cannot be associated with any one group of factors, because the nature of the relationship of plants with different categories of pathogens is too diverse.

In the first half of the XX century. in our country, only an assessment was made of the resistance of plant varieties and species to diseases and parasites (cereal crops to rust and smut, sunflower to broomrape, etc.). Later, they began to conduct selection for immunity. This is how sunflower varieties bred by E. M. Pluchek (Saratovsky 169 and others), resistant to broomrape (Orobanche sitapa) of race A and sunflower moth, appeared. The problem of combating broomrape race B "Evil" was removed for many years thanks to the work of V. S. Pustovoit, who created a series of varieties resistant to broomrape and moths. V. S. Pustovoit developed a seed production system that allows long time maintain the stability of sunflower at the proper level. In the same period, varieties of oats resistant to crown rust were created (Verkhnyachsky 339, Lgovsky, etc.), which have retained resistance to this disease to this day. From the mid-1930s, P.P. Lukyanenko and others began breeding for wheat resistance to leaf rust, M.F. Ternovsky began work on creating tobacco varieties resistant to a complex of diseases. Using interspecific hybridization, he developed tobacco varieties resistant to tobacco mosaic, powdery mildew and downy mildew. Successfully conducted selection for the immunity of sugar beets to a number of diseases.

Varieties resistant to powdery mildew (Hybrid 18, Kirghizskaya odnosemyanka, etc.), cercosporosis (Pervomaisky polyhybrid, Kuban polyhybrid 9), downy mildew (MO 80, MO 70), root beetle and clamp rot (Verkhneyachskaya 031, Belotserkovskaya TsG 19) were obtained.

A. R. Rogash and others successfully worked on the selection of flax for immunity. Varieties P 39, Orshansky 2, Tvertsa with increased resistance to Fusarium and rust were created.

In the mid-1930s, K. N. Yatsynina obtained tomato varieties resistant to bacterial canker.

A number of interesting and important works for the creation of varieties vegetable crops, resistant to carina and vascular bacteriosis, were carried out under the guidance of B. V. Kvasnikov and N. I. Karganova.

With varying success, cotton was selected for immunity to verticillium wilt. The variety 108 f, bred in the mid-30s of the last century, retained stability for about 30 years, but then lost it. The varieties of the Tashkent series that replaced it also began to lose resistance to wilt due to the emergence of new races of Verticillium dahliae (0, 1, 2, etc.).

In 1973, a decision was made to establish laboratories and departments for plant immunity to diseases and pests at breeding centers and institutes for plant protection. An important role in the search for sources of sustainability was played by the Institute of Plant Industry. N. I. Vavilov. The world collections of cultivated plant specimens collected at this institute still serve as a fund of resistance donors of various crops necessary for breeding for immunity.

After the discovery by E. Stekman of physiological races in the causative agent of stem rust of cereals, similar work was launched in our country. Since 1930, the VIZR (V. F. Rashevskaya et al.), the Moscow Agricultural Experimental Station (A. N. Bukhgeim et al.), and the All-Union Breeding and Genetic Institute (E. E. Geshele) began to study physiological races brown and stem rust, smut. In the postwar years, the All-Russian Research Institute of Phytopathology began to deal with this problem. Back in the 1930s, A.S. Burmenkov, using a standard set of differentiating varieties, showed the heterogeneity of races of rust fungi. In subsequent years, especially in the 1960s, these works began to develop intensively (A. A. Voronkova, M. P. Lesovoi, and others), which made it possible to reveal the reasons for the loss of resistance by some varieties with a seemingly unchanged racial composition of the fungus. Thus, it was found that race 77 of the causative agent of wheat leaf rust, which prevailed in the 70s of the XX century. in the North Caucasus and southern Ukraine, consists of a series of biotypes differing in virulence, formed not on wheat, but on susceptible cereals. The studies of smut fungus races, begun at VIZR by S.P. Zybina and L.S. Gutner, as well as by K.E. Murashkinsky in Omsk, were continued at VIR by V.I. Tymchenko at the Institute of Agriculture of the Non-Chernozem Zone.

N. A. Dorozhkin, Z. I. Remneva, Yu. V. Vorob’eva, and K. V. Popkova were very productive in studying the races of Phytophthora infestans. In 1973 Yu.T.Dyakov together with T.A. Kuzovnikova et al. discovered the phenomenon of heterokaryosis and parasexual process in Ph. infestans, allowing to some extent to explain the mechanism of variability of this fungus.

In 1962 P.A.Khizhnyak and V.I. Yakovlev discovered aggressive races of the causative agent of potato cancer Synchythrium endobioticum. It was found that at least three races of S. endobioticum are distributed on the territory of our country, affecting potato varieties resistant to the common race.

In the late 70s - early 80s of the last century, A. G. Kasyanenko studied the physiological races of the fungus Verticillium dahliae; tobacco - A. A. Babayan.

Thus, the study of plant immunity to infectious diseases was carried out in our country in three main areas:

The study of race formation of pathogens and analysis of the structure of populations. This led to the need to study the population composition within species, the mobility of the population, the patterns of appearance, disappearance or regrouping of individual members of the population. The doctrine of races arose: accounting for races, forecasting and regularities in the appearance of some races and (or) the disappearance of others;

assessment of disease resistance of existing varieties, search for resistance donors and, finally, the development of resistant varieties.

Innate, or natural, immunity is the property of plants not to be affected (not damaged) by a particular disease (pest). Innate immunity is inherited from generation to generation.

Innate immunity is divided into passive and active immunity. However, the results of numerous studies lead to the conclusion that the division of plant immunity into active and passive is very conditional. At one time, this was emphasized by N.I. Vavilov (1935).

The increase in plant resistance under the influence of external factors, which occurs without changing the genome, is called acquired or induced resistance. Factors whose effect on seeds or plants leads to an increase in plant resistance are called inducers.

Acquired immunity is the ability of plants not to be affected by one or another pathogen that arose in plants after the transfer of a disease or under the influence of external influences, especially plant cultivation conditions.

Plant resistance can be increased by various methods: the introduction of microfertilizers, changing the timing of planting (sowing), seeding depth, etc. Methods for gaining resistance depend on the type of inductors, which can be biotic or abiotic in nature. Techniques that promote the manifestation of acquired resistance are widely used in agricultural practice. So, the resistance of cereal crops to root rot can be increased by sowing spring crops at the optimum early, and winter crops at the optimum late dates; resistance of wheat to smut, which affects plants during seed germination, can be increased by observing optimal timing sowing.

Plant immunity may be due to the inability of the pathogen to infect plants of this species. So, grain crops are not affected by late blight and potato scab, cabbage - by smut diseases, potatoes - by rust diseases of cereal crops, etc. In this case, immunity is manifested by the plant species as a whole. Immunity based on the inability of pathogens to cause infection of plants of a certain species is called non-specific.

In some cases, immunity may not be manifested by the plant species as a whole, but only by a particular variety within this species. In this case, some varieties are immune and are not affected by the disease, while others are susceptible and are affected to a great extent by it. So, the causative agent of potato cancer Synchytrium endobioticum infects the Solanum species, however, there are varieties inside it (Kameraz, Stoilovy 19, etc.) that are not affected by this disease. Such immunity is called varietal specific. It is of great importance in breeding resistant varieties of agricultural plants.

In some cases, plants may be immune to pathogens of various diseases. For example, sort winter wheat may be immune to both powdery mildew and brown stem rust. The resistance of a plant variety or species to several pathogens is called complex or group immunity. The creation of varieties with complex immunity is the most promising way to reduce crop losses from diseases. For example, wheat Triticum timophevi is immune to smut, rust, and powdery mildew. Tobacco varieties are known that are resistant to the tobacco mosaic virus and the downy mildew pathogen. By zoning such varieties in production, it is possible to solve the problem of protecting a particular crop from major diseases.

Immunity is the body's resistance to infectious disease upon contact with its pathogen and the presence of conditions necessary for infection.
Particular manifestations of immunity are stability (resistance) and endurance. Sustainability It consists in the fact that plants of a variety (sometimes a species) are not affected by a disease or pests, or are affected less intensively than other varieties (or species). Endurance called the ability of diseased or damaged plants to maintain their productivity (the quantity and quality of the crop).
Plants can have absolute immunity, which is explained by the inability of the pathogen to penetrate into the plant and develop in it even under the most favorable external conditions for this. For example, coniferous plants are not affected by powdery mildew, and deciduous - by shute. In addition to absolute immunity, plants may have relative resistance to other diseases, which depends on the individual properties of the plant and its anatomical-morphological or physiological-biochemical characteristics.
Distinguish between innate (natural) and acquired (artificial) immunity. innate immunity - this is a hereditary immunity to the disease, formed as a result of directed selection or long-term joint evolution (phylogenesis) of the host plant and the pathogen. acquired immunity - this is resistance to a disease acquired by a plant in the process of its individual development (ontogenesis) under the influence of certain external factors or as a result of the transfer of this disease. Acquired immunity is not inherited.
Innate immunity can be passive or active. Under passive immunity understand resistance to a disease, which is provided by properties that manifest themselves in plants regardless of the threat of infection, i.e. these properties are not defensive reactions of a plant to a pathogen attack. Passive immunity is associated with the features of the form and anatomical structure plants (crown shape, stomata structure, the presence of pubescence, cuticle or wax coating) or with their functional, physiological and biochemical characteristics (the content of compounds in the cell sap that are toxic to the pathogen, or the absence of substances necessary for its nutrition, the release of phytoncides).
active immunity - this is resistance to a disease, which is provided by the properties of plants that appear in them only in the event of a pathogen attack, i.e. in the form of defensive reactions of the host plant. A prime example An anti-infective defense reaction can be a hypersensitivity reaction, which consists in the rapid death of resistant plant cells around the site of pathogen introduction. A kind of protective barrier is formed, the pathogen is localized, deprived of nutrition and dies. In response to infection, the plant can also release special volatile substances - phytoalexins, which have an antibiotic effect, delaying the development of pathogens or suppressing the synthesis of enzymes and toxins by them. There are also a number of antitoxic protective reactions aimed at neutralizing enzymes, toxins and other harmful waste products of pathogens (restructuring of the oxidative system, etc.).
There are such concepts as vertical and horizontal stability. The vertical one is understood as the high resistance of a plant (variety) only to certain races of a given pathogen, and the horizontal one is a certain degree of resistance to all races of a given pathogen.
The resistance of plants to diseases depends on the age of the plant itself, the physiological state of its organs. For example, seedlings can only lodging at an early age and then become resistant to lodging. Powdery mildew affects only young leaves of plants, and old ones, covered with a thicker cuticle, are not affected or are affected to a lesser extent.
Environmental factors also significantly affect the resistance and hardiness of plants. For example, dry weather during the summer reduces resistance to powdery mildew, and mineral fertilizers make plants more resistant to many diseases.

In contrast to medicine and veterinary medicine, where acquired immunity is of decisive importance in the protection of humans and animals, acquired immunity has been used very little in practical phytopathology until recently.

In plants there is a significant circulation of juices, although not in closed vessels. When solutions of mineral salts or other substances are applied to parts of a plant, after some time these substances can be found in other places of the same plant. Based on this principle, the Russian scientists I. Ya. Shevyrev and SA Mokrzhetsky developed the method of foliar plant nutrition (1903), which is widely used in agricultural production. The presence of sap circulation in plants can explain the appearance of root cancer tumors far from the place of introduction of the causative agent of this disease - Pseudomonas tumefaciens Stevens. This fact also indicates that the formation of tumors is not only a local disease, but the whole plant as a whole responds to the disease.

Acquired immunity can be created in various ways. In particular, it can be created by vaccination and chemical immunization of plants, by treating them with antibiotics, as well as by some methods of agricultural technology.

In animals and humans, the phenomena of acquired immunity resulting from past illness and vaccination with weakened cultures of the pathogen are well known and studied in detail.

The great successes achieved in this area served as a stimulus for the search for similar phenomena in the field of phytoimmunology. However, the very possibility of the existence of acquired immunity in plants was at one time called into question on the grounds that plants do not have a circulatory system, and this excludes the possibility of immunization of the entire organism. The acquired immunity of plants was considered as an intracellular phenomenon, excluding the possibility of diffusion of the substances formed in the affected cells into neighboring tissues.

It can be considered established that in some cases the resistance of plants to infection increases both after the disease and as a result of vaccination. As a vaccine, waste products of pathogens (culture medium), weakened cultures and preparations from microorganisms killed by anesthesia or heating can be used. In addition, bacteriophage prepared in the usual way, as well as serum from animals immunized with a microorganism pathogenic for plants, can be used for immunization. Immunizing substances are administered primarily through the root system. It is also possible to spray into the stems, apply as a lotion, spray on the leaves, etc.

Methods of artificial immunization, widely used in medicine and veterinary medicine, are not very promising in plant growing practice, since both the preparation of immunizing agents and their use are very laborious and expensive. If we take into account that immunization is not always sufficiently effective and its action is very short-lived, and also that the immunization process, as a rule, depresses the plant, it becomes clear why the results of work in the field of acquired immunity are not yet used in agricultural practice.

There are isolated cases of plant immunization as a result of the transferred viral infection. In 1952, Canadian scientists Gilpatrick and Weintraub showed that if the leaves of Dianthus borbatus are infected with the necrosis virus, then uninfected leaves become resistant. Subsequently, similar observations were made by other researchers on many plants infected with various viruses. At present, facts of this kind are considered as phenomena of immunity acquired as a result of a disease.

In search of a protective factor arising in the tissues of virus-resistant forms of plants, researchers first of all turned to the hypersensitivity reaction, attributing a protective role to the polyphenol-polyphenol oxidase system. However, experimental data on this issue did not give definite results.

In some works, it is noted that the juice from the cells of the immune zone that forms around the necrosis, as well as from tissues that have acquired immunity, has the ability to inactivate the virus. The isolation and study of this antiviral factor showed that it has a number of properties similar to animal interferon. Interferon-like protein, like animal interferon, is found only in virus-infected resistant tissues, easily diffuses from infected cells to uninfected ones, and does not have antiviral specificity. It inhibits the infectivity of various plant-specific viruses from different families. The antiviral factor is active against viruses both in vitro, i.e. when mixed with an extract from virus-infected leaves, and in vivo, i.e. when it is introduced into the leaves of a plant. It is believed that it can act either directly on the particles of the virus, or on the process of its reproduction, suppressing metabolic processes, as a result of which new viral particles are synthesized.

The phenomena of acquired immunity may include an increase in resistance to diseases caused by chemicals. Soaking seeds in solutions of various chemical compounds increases the resistance of plants to diseases. The properties of immunizers are macro- and microelements, insecticides and fungicides, growth substances and antibiotics. Pre-sowing soaking of seeds in solutions of trace elements also increases the resistance of plants to diseases. The healing effect of microelements on the plant was preserved in some cases for the next year.

Phenolic compounds are effective as chemical plant immunizers. Soaking seeds in solutions of hydroquinone, paranitrophenol, orthonitrophenol, etc., can significantly reduce the susceptibility of millet to smut, watermelons, eggplant and pepper - withering, oats - crown rust, etc.

Resilience caused by various chemical compounds, as well as natural, genetically determined, can be active and passive. For example, chemical treatment of seeds and plants can increase their mechanical resistance (increase the thickness of the cuticle or epidermis, affect the number of stomata, lead to the formation of internal mechanical barriers to the path of the pathogen, etc.). In addition, most chemical plant immunizers are substances of intraplant action, i.e., penetrating into the plant, they affect its metabolism, thereby creating unfavorable conditions for the nutrition of the parasite. Finally, some chemical immunizers can act as agents that neutralize the action of pathogen toxins. In particular, ferulic acid, being an antimetabolite of pyricularin, a toxin of Piricularia oryzae, increases rice resistance to this pathogen.

The term "immunity" (means "liberation" from something) - complete immunity of the body to an infectious disease.

At present, the concept of plant immunity is formulated as the immunity to diseases manifested by them in the case of direct contact of them (plants) with pathogens that can cause this disease if the conditions necessary for infection exist.

Along with complete immunity (immunity), there are also very similar concepts - stability or resistance and endurance or tolerance.

Resistant (resistant) consider those plants (species, varieties) that are affected by the disease, but to a very weak extent.

Endurance (tolerance) call the ability of diseased plants not to reduce their productivity (the quantity and quality of the crop, or to reduce it so slightly that it is practically not felt)

Susceptibility ( susceptibility) – the inability of plants to resist the infection and spread of the pathogen in its tissues, i.e. the ability to become infected upon contact with a sufficient amount of an infectious agent under appropriate external conditions.

Plants have all of the listed types of manifestation of immunity.

Immunity (immunity) of plants to diseases can be congenital and be inherited. Such immunity is called natural.

Innate immunity can be active or passive.

Along with natural immunity, plants may be characterized by acquired (artificial) immunity - the property of plants not to be affected by one or another pathogen, acquired by the plant in the process of ontogenesis.

Acquired immunity can be infectious if it occurs in a plant as a result of recovery from a disease.

Non-infectious acquired immunity can be created with the help of special techniques under the influence of the treatment of plants or seeds with immunizing agents. This type of immunity is of great importance in the practice of agricultural protection. plants from disease.

Increasing the resistance of plants to diseases using artificial techniques is called immunization which can be chemical or biological.

Chemical immunization is to use different chemical substances capable of increasing plant resistance to diseases. Fertilizers, trace elements, antimetabolites are used as chemical immunizers. Acquired non-infectious immunity can be created through the use of fertilizers. Thus, an increase in the dose of potash fertilizers increases the keeping quality of root crops during storage.

Biological immunization consists in using other living organisms or their metabolic products as immunizers (antibiotics, weakened or killed cultures of phytopathogenic organisms, etc.).

Plant resistance can be achieved by treating them with vaccines - weakened cultures of pathogens or extracts from them.

Lecture 5

Developmental biology of insects

Peculiarities external structure insects.

2. Development of insects. Postembryonic development:

a) larval phase;

b) pupal phase;

C) the phase of an adult insect.

Development cycles of insects.

1. Features of the external structure (morphology) of insects.

Entomology is the science of insects ("entomon" - insect, "logos" - doctrine, science).

The body of insects, like all arthropods, is covered on the outside with a dense cuticle. Forming a kind of shell, the cuticle is the outer skeleton of the insect and serves as a good defense against the adverse effects of the external environment. The internal skeleton of the insect is poorly developed, in the form of outgrowths of the external skeleton. A dense chitinous cover is slightly permeable and protects the body of insects from water loss and, consequently, from drying out. The external skeleton of insects is also of mechanical importance. In addition, internal organs are attached to it.

The body of an adult insect is subdivided into a head, thorax, and abdomen and has three pairs of jointed legs.

The head consists of approximately five to six segments fused to one another; chest - out of three; the abdomen can have up to 12 segments. The ratio of sizes between the head, chest and abdomen can be different.

Head and its appendages

The head bears a pair of compound eyes, often one to three simple eyes, or ocelli; mobile appendages - antennae and mouth organs.

The shape of the head of insects is diverse: rounded (flies), laterally compressed (locust, grasshopper), elongated in the form of a ready-made tube (weevils).

Eyes. The organs of vision are represented by complex and simple eyes. Complex or faceted, the eyes in one pair are located on the sides of the head and consist of many (up to several hundred and thousands) visual units, or facets. In this regard, in some insects (dragonflies, male flies and bees), the eyes are so large that they occupy most of the head. Compound eyes are present in most adult insects and in larvae with no complete transformation.

Simple dorsal eyes, or ocelli, in a typical case among three, are located in the form of a triangle on the forehead and crown between the compound eyes. As a rule, ocelli are found in adult, well-flying insects.

Simple lateral eyes, or stemmas, form two pairs of groups located on the sides of the head. The number of eyes varies from 6 to 30. Inherent mainly in insect larvae with complete transformation, less common in adult insects lacking compound eyes (fleas, etc.).

Antennae, or antennae represented by one pair of jointed formations located on the sides of the forehead between or in front of the eyes in the antennal fossae. They serve as organs of touch and smell.

Mouth organs have undergone significant changes from the gnawing type when eating solid food to various modifications of the sucking type when taking liquid food (nectar, plant sap, blood, etc.). There are: a) gnawing-licking; b) piercing-sucking; c) sucking and d) licking types of mouth organs.

The type of damage to the plant depends on the method of nutrition and the structure of the oral organs, by which it is possible to diagnose pests and select a group of insecticides to combat them.

Breast and its appendages

Breast structure. The thoracic region of the insect consists of three segments: 1) anterior, 2) middle, and 3) metathorax. Each segment, in turn, is subdivided into an upper half-ring-back, a lower half-ring-breast and side walls - barrels. Half rings are called: pronotum, prothorax, etc.

Each segment of the thorax bears a pair of legs, and in winged insects, the mesothorax and metathorax bear a pair of wings.

The structure and types of legs. The leg of an insect consists of: a coxa, a trochanter, a thigh, a lower leg and a paw.

According to the way of life and the level of specialization of certain groups of insects, they have Various types legs. So running legs, with elongated thin segments, are characteristic of cockroaches, bedbugs, ground beetles and other fast-running insects; walking legs with shorter segments and extended tarsi are most typical of leaf beetles, barbels, and weevils.

Adaptation to the conditions of life or to the methods of movement contributed to the specialization of the front or hind legs. So the bear, which most of life cycle carried out in the soil, digging forelegs arose with a shortened and widened femur and tibia, and an underdeveloped tarsus.

The hind legs of acridoids, grasshoppers, and crickets have been transformed into jumping ones, characterized by strong thickened femurs and the absence of a trochanter.