PLANT BREEDING AND THE THEORY OF PHASIC DEVELOPMENT OF PLANTS
T. D. Lysenko in collaboration with I. I. Prezent

The Individual Development of the Hereditary Foundation of Plants

Plant breeding must be based on the science of genetics, the science of heredity. Moreover, it presents very definite demands to genetics, namely, to develop that department of this science which will make it possible consciously to direct the form-building of varieties and breeds along economically valuable lines, to work out the theoretical principles of determining the properties and characters of varieties, breeds, etc. Important as many of the achievements of genetics may be for breeding (methods of inducing mutations, the theories of pure lines, of homozygosity and heterozygosity, establishment of the fact of dominance, establishment of the fact of the segregation of the properties of hybrids in a series of generations, etc.), this science has completely divorced itself from the study of the laws governing the individual development of plants. As a result the branch of genetics that deals with the law governing the hereditary determination of characters has been largely converted into one advocating a theory of the simple transmission, combination and segregation of the rudiments of characters and of the characters themselves, over a number of generations. It is along these lines that genetics seeks to establish the laws of the inheritance of characters, drawing a direct, in no way mediated, mental projection [66] from characters and groups of characters to the rudiments, the "genes," and establishing a similarly unmediated correlation between sections of chromosomes, their location and interrelation, and the characters of organisms. In this, genetics has, as it were, unbiologized itself, has divorced itself from the Darwinian biological study of the hereditary "factors." Genetics takes no part whatever, and its official representatives are not interested, in the study of the law of development of characters but tries to discover the law governing their simple presence or absence on the basis of the abstract mathematical probability of factors "meeting."

But "characters," including those of economic importance that interest the plant breeder, such as drought resistance, frost hardiness, surplus moisture resistance, resistance to various pests, duration of vegetative period, size of grain, vitreousness and farinaceousness, crown the edifice. They are the most concrete and complex formations in the plant organism. These "characters" are only the final result of the organism's development. The development of organs and characters is linked with the conditions they require, with the concomitant influence of varied factors upon the form-building of organs and their characters. Moreover, the development of organs, groups of organs and their characters and properties proceeds on the basis of separate phases of development (biologically necessary stages in the life of the organism). The latter, in their turn, develop in interaction with the special conditions of existence which they biologically need. Unable, however, to declare that development is concrete and full of contradictions, present-day bourgeois genetics evades the complex laws governing the formation of characters and groups of characters and tries to deduce their presence or absence directly from the genotype. Precisely here we find proof that the science of genetics reflects the general anarchy prevailing in the development of bourgeois science and, consequently, has divorced itself from the study of the laws of individual development (leaving this study to a special science, the "mechanics of development," divorced in its turn from the laws of heredity and from philogenesis); that it has mapped out for itself a historical path which takes it far away from the inherent dialectical logic of cognition, a logic objectively dictated by its subject. Instead of proceeding from the establishment of the laws of development of the hereditary foundation into the general law of ontogenesis, into phases, and only of the 'latter into organs and characters; instead of proceeding only in the final analysis to the ascertainment of the laws governing the most complex result of development, namely characters, genetics in its course of development has gone straight to find out the laws governing the correlation of characters and rudiments (genes). It is but natural that, following this path, the science of genetics should become largely formal as regards its chief theoretical constructions and should be unable, in an adequate degree, to be for plant breeding what it necessarily must be—the theoretical basis of a guide to action. Failing to receive concrete guidance to action from genetics, plant [67] breeding was obliged to solve many of its problems as if the science of genetics did not exist.

To produce a variety, plant breeding must choose a parental pair for crossing. By what should it be guided in this? Genetics is silent on this score, and plant breeding is obliged to grope in the dark in the endeavour, empirically, in the lottery of crossings, to stumble upon the needed result. As we shall show later on, breeders ought to know beforehand, before the crossing, which of the parents' characters will dominate, in the offspring, but geneticists can tell us nothing about this.

Incidentally, genetics is not always silent. Sometimes it reacts to these fundamental requirements of plant breeding. Which characters will be dominant in the offspring? We will tell you, but only after we have made the crossing and see what the offspring looks like. What pairs should be taken for crossing? Take as many as possible with the particular characters in which the plant breeder is interested, in the hope that, by chance, the needed combination may result.

But this needed combination will result (if it results at all) only in one case out of many thousands. To obtain an economically valuable variety, one better than any now extant in a given district, it is necessary to combine in it quite a large number of favourable characters: required vegetative period, resistance to frost, to excessive moisture, to drought and to various pests, no lodging, no shattering, etc.

On what scale must work be conducted in order to obtain the needed combination in the course of segregation? True, we are able to enlarge the scale of our work; but only up to a certain limit. One must not lose one's sense of proportion. In order to add only 10 genes to Kooperatorka, for example, it is necessary, according to Academician Sapegin, to grow hundreds of thousands of plants: only in that case will there be a chance of one desirable combination being obtained among the segregates. But is there any guarantee that this combination will be detected among the millions? It is highly probable that this slightly probable combination (one chance in hundreds of thousands) will be overlooked.

Does this give profound theoretical guidance to quick and precise practical action? Empirical plant breeding can "work" in this way even without genetics. And, unfortunately, it is obliged to work in this way, only very, very rarely producing varieties which after being tested are found to be useful in some districts, but in most cases only promising to produce a variety in the more or less distant future.

In many cases, under these circumstances, the State Cereal Variety Trial Commission has to serve as the real "plant breeder" and to locate a suitable district for a variety that was found unsuitable for the district to which it was originally assigned. For example, the winter wheat Kooperatorka, raised by the Odessa station, is now grown in an extremely limited area in the Ukrainian S.S.R., but is extensively grown in the Caucasus and Trans-Caucasus. The winter wheat Stepnyachka, likewise raised by the Odessa [68] station, is not grown in the Ukrainian S.S.R., but thrives in some of the districts in the North Caucasus. Hordeiforme 010, raised by the Dniepropetrovsk station, finds no place among the crops of the Ukrainian S.S.R., but occupies a considerable area in the Trans-Urals. The winter wheat Dürabl, raised by the Ivanovskaya station and intended for the eastern forest-steppe region of the Ukrainian S.S.R., was found to be unsuitable here, but suitable for the northern regions (Kirov). The spring wheat Melanopus 069, raised by the Krasnokutsk station, is extensively grown in the steppe region of the Ukrainian S.S.R. Milturum 162, raised by the Kharkov station for the forest-steppe region of the Ukrainian S.S.R., is recommended for the Odessa Region. Numerous other cases could be cited to show that most of the varieties raised by plant-breeding institutions for the districts they serve are found to be unsuitable for the particular district, but are extensively grown in quite another, often sharply differing district, i.e., are "sent out into the world" not by the plant breeders, but by the State Cereal Variety Trial Commission. All this is because plant breeding lacks a sufficiently firm theoretical basis for its activities.

Here we must emphasize that plant breeding has been responsible for a large number of good varieties of different crops. But in many cases these varieties have been raised by breeders who have made a deep study of plant life and are guided by their own long years of experience, which quite often is at variance with the rules laid down by official science. Of these plant breeders, however, only a few, like I. V. Michurin, built up and developed a theory of plant breeding on the basis of their many years of experience.

In most cases, the experience which has enabled veteran plant breeders to raise different varieties has not been analyzed or generalized theoretically, has been kept outside the realm of science, as it were, has remained the local, personal knowledge of individual plant breeders.

Falling to analyze the process of plant breeding, or confining this analysis to a calculation of segregation, failing to obtain sufficiently effective advice from genetics, plant breeding is proceeding along empirical lines. As regards genetics "forecasting" dominant properties, this too is done after empirical crossing, and thus remains simply an empirically-inductive statement of fact.

Failure to analyze observed phenomena makes it impossible actually to predict before crossing what will dominate and to ascertain the levers that control this process.

We cannot keep marking time on the old genetic plant-breeding positions. A bold and determined change in the very methods of research is needed here.

Of course, we must assimilate the legacy of the whole of the preceding development of science. At the same time, however, we must firmly bear in mind the methodologically metaphysical line of thought of the protagonists of bourgeois science. We must fight uncompromisingly for the reconstruction of the genetic plant-breeding theory, for the building of our own genetic [69] plant-breeding theory on the basis of the materialist principles of development, which actually reflect the dialectics of heredity. Only by consciously building such a theory can the breeding process be provided with real guidance suitable for the requirements of socialist production.

To overcome the formalism of direct projection from "characters" to "genes" and vice versa, it is necessary to discover and reveal the path of development of an organism's properties, to analyze them according to degree of concretization, to ascertain the law of development of the hereditary foundation in a series of generations, and not go out in search of a simple transmission of factors and characters over a series of generations. This work of bridging the gulf between the study of the hereditary foundation and the study of the individual development of this foundation was undertaken by the Laboratory of the Physiology of Plant Development of the Institute of Selection and Genetics (Odessa), which began to breed varieties in a new way. We proceeded from the following theoretical propositions.

1This, of course, does not mean that it is impossible consciously to influence the building up of the hereditary basis. The very opposite is the case, but we are not discussing this now.

The development of present-day plant organisms always starts from some structural foundation—the hereditary basis (genotype) which bears the "impress" of all preceding phylogenetic history. This "impress" serves as the general background and determines the progress of the necessary stages of individual development, relatively sets the general tone of the entire cycle of the organism's development (in plants, from seed to seed). Being the starting point of the plant organism's development, the hereditary basis (genotype) accordingly determines the necessity within the frame of which the entire subsequent individual development proceeds. The organism is not free to choose its hereditary basis. It begins its development from this basis as something already given.1

The organism's hereditary foundation, created by the fusion of two ancestral bases-maternal and paternal-which differ in some degree (heterozygote), is made complex by the union of the two lines of the phylogenetic history of its ancestors. Thus, this complex hereditary foundation (heterozygote) is richer in aspects and, consequently, in potentialities of development, than either of the parent homozygotes.

The zygote thus formed (by the fusion of two gametes) contains a wealth of potentialities for the development of the organism's properties in the shape of an impress of the phylogenetic line. The heterozygote combines the potentialities of both the maternal and paternal lines, with all the wealth of aspects of their hereditary bases, which they contributed to the heterozygote.

How will development proceed? What will determine and condition it? Will all the aspects of the complex (heterozygote) hereditary foundation make themselves equally felt in the individual history of the first generation (F1), and what will determine the actual development of the different aspects [70] of the hereditary foundation? All this must be ascertained in order to become proficient in the knowledge of the law of genetics and place it at the service of socialist, planned breeding of varieties.

The hereditary foundation (zygote) contains in its multifarious aspects only the possibility of a plant's development from one phase to another. True, this possibility is absolutely real: not just any organic form, of any nature and sequence of phases, can develop from a given hereditary foundation. The hereditary foundation contains the general regularities of a plant's varietal nature only as a real possibility. For this possibility to develop into actuality, into the plant's developmental phases (and for the latter to lead to the formation of organs and characters), conditions of existence suitable to the nature of the plant are required.

When speaking of "conditions of existence" and acting accordingly in practice, we distinguish the "conditions of existence" of the process of development from the plant's "habitat" as well as from the external "influencing factors." Not everything in the plant's "habitat" is a factor that really influences the organism's course of development. And not every "influencing factor" is a "condition of existence" of the organism's development.

The "conditions of existence" of a plant's cycle of development are those essential conditions without which there is no development of phases, organs and characters in the plant's progress towards reproduction. The "conditions of existence" of a plant's cycle of development are the result of natural selection in the course of the many thousand years' history of organisms. The organism's interrelation with the conditions of existence of a plant's stages of development includes the organism's relative adaptedness to these conditions created by natural selection and, consequently, includes the requirement of these conditions by the organism as an indispensable premise for the stages of its individual development. Only complete disregard of Darwin's scientific legacy can explain why Klebs and other "mechanists of development" reject the adaptive requirements of plants in the process of form-building, and are unable to distinguish, in their theory and scientific experimental practice, "conditions of existence" from "factors that influence" form-building.

In the process of development of a plant's hereditary foundation and the formation of the phases of its cycle, organs and characters (from seed to seed), the plant can be influenced by various factors: electricity, ionization, temperature, water, etc. But by no means all these factors are necessary conditions of existence of a plant's development from its hereditary foundation to reproduction; not all are essential conditions called for by the very nature of the plant organism as a result of the adaptation of its varietal, specific, etc., nature to these conditions of its development.

Accordingly, every phase of a plant's development calls for special conditions of existence during the whole period of the given phase. A plant cannot pass through the first phase (vernalization) unless the just slightly-sprouted seed or the green plant is given a suitable dosage (specific for [71] each variety) of thermic and moisture conditions (together with the other components: access of air, etc.). The second phase requires other conditions of existence, including without fail light in doses suitable for the given variety. During the first phase of development (vernalization), there may or may not be light or darkness, although, of course, they will always be present, for it is impossible to avoid keeping the just slightly-sprouted seeds either in light (of some degree) or in darkness. But neither light nor darkness are essential conditions for the whole of this phase of a plant's development. As regards the second phase (the "photo" phase), suitable light (in specified doses for each variety and species) is an essential condition of its existence. Of course a definite degree of moisture, thermic factors, light, and many other elements not needed at all, or not needed at the given moment for a plant's development, may sometimes, instead of being inactive elements of the habitat, become really active factors, influencing some of the processes in a plant when going through a given phase. But if the plant's nature does not require these factors, the plant can pass through that phase without them. However, without the conditions of existence to which the given phase is adapted, the phase will not develop at all. "Winter" varieties are such only because in the spring their vernalization phase does not find in the fields the conditions of development required by their varietal nature.

Absolute proof and documentary confirmation of this is found in numerous experiments conducted in our laboratory for the purpose of ascertaining the conditions of existence of various plant phases. Seeds of the winter wheat Stepnyachka, which usually does not fruit in one period of vegetation, were kept with 55% moisture content at 0º-2ºC. temperature for 45 days (the conditions of vernalization for this variety) and subsequently, when sown, they were kept under a 9-hour day. As a result, the plants failed to ear and, consequently, did not go through their whole cycle of development from seed to seed (Fig. 23, second pot, left to right). When, however, seeds of the same variety were kept under the same moisture and thermal conditions and for the same length of time as those in the first case, and then, after being sown, were kept in continuous light for 30 days, the plants eared and ripened, i.e., they passed through the whole cycle of development nature had assigned for them (Fig. 23, first pot on right). When seeds of the same variety of winter wheat were kept in continuous light for the same length of time as those mentioned above, without providing them, before sowing, with moisture (55%) and thermal conditions (0º-2º C.), i.e., without creating the conditions for passing through the vernalization phase, the plants failed to ear. The records of these and similar experiments (Fig. 24) serve as indisputable documentary proof that there are phases, stages, in the development of plants which call for their own specific conditions of existence.

To offer these conditions to another phase (Fig. 24, first pot on left, and Fig. 23) means ignoring the plant's biological adaptational [72] requirements and, at best, converting "conditions of existence" into simple "influencing factors," and even into mere elements of an indifferent environment.


Fig. 23. In each pair of pots, the plants in the left pots are from unvernalized seeds and in the right pots from vernalized seeds
The plants in the two pots on the left were grown under short-day conditions, those in the two pots on the right were grown in continuous light. Only the plants grown from vernalized seeds in continuous light eared (pot on extreme right). This experiment shows that continuous light cannot serve as a substitute for the low temperature needed for passage through the vernalization phase. The experiment also shows that alter passing through the vernalization phase, wheat plants need the long day for passing the photo phase

1The methodological mistakes made in experiments in "vernalization", by means of light were examined by Lysenko in the paper he read at the All-Union Conference on Winter Hardiness on June 24, 1934, and at a scientific conference of the Institute of Genetics of the Academy of Sciences of the U.S.S.R. on January 6, 1935.

Therefore, all attempts to force a plant to go through a given phase of development by substituting any other conditions for those the plant requires, for example, by substituting light for temperature in the first phase (vernalization), as the "repudiators" of the phasic development of plants try to do, are misguided and methodologically fallacious in their very conception.1

[73]


Fig. 24. Winter wheat Novokryrnka 0204
This experiment shows the same as was shown in the case of Stepnyachka. The plants in the first pot on the left (from ordinary seeds) were grown in continuous light. The plants in the second pot from the left (from vernalized seeds) were grown in continuous light. The plants in the third pot from the left (from vernalized seeds) were grown in continuous light for the first seventeen days and under 10-hour-day conditions for the next 32 days The plants in the fourth pot from the left (from ordinary seeds) were grown under 10-hour-day conditions. The plants in the fifth pot (from vernalized seeds) were grown under 10-hour-day conditions

[74]

Confusing "conditions of existence of development" with "influencing factors" also leads to confusing and identifying "vernalization" with "stimulation." It is possible and necessary to find numerous means of accelerating different processes in the life of plants. But to prove that it is correct to identify "vernalization" with "stimulation," the stimulators must force known winter wheats to fruit by methods of their own invention without introducing, and even directly eliminating, the established conditions of existence of the phases of development. Perhaps the adherents of stimulation will undertake to do this? Otherwise we have a right to demand that they and the "vernalizers" should not irresponsibly introduce confusion into the work of vernalization and into the principles underlying methods already being applied on hundreds of thousands of hectares of crop fields, where their soundness has been proved. Confusion in such a matter is far from being the private affair of this or that author.


Fig. 25. Winter wheat Ukrainka
This illustration shows the direct dependence of the characters "winter habit" and "spring habit" on the course of the vernalization phase. For the Ukrainka to pass through the vernalization phase, its hereditary foundation needs conditions which are usually absent in the spring in the localities where this variety is grown. As a result it turns out to be a winter plant since it cannot, under these conditions, pass through its cycle of development in the course of one summer. Under these conditions Ukrainka develops neither straw nor ears, i.e., is a "winter" plant (sheaf on left). The Ukrainka sheaf on the right passed through the vernalization phase (in the seed state, before sowing) and, finding in the field the conditions for the development of all succeeding phases, the tufts behaved like spring plants

A plant's phases of development and conditions of existence constitute a general law, a general type in its developmental cycle. But in each of these phases of its life the plant enters, and cannot avoid entering, into innumerable connections with many other factors of inorganic and organic nature. The latter always somewhat deflect and individualize the general scheme of development of a plant of a given variety, species, etc. A plant's different organs and characters that develop on the basis of definite phases, require in their turn, their own conditions of existence and are also inevitably subjected to the influence of particular factors. A plant's concrete characters are the result of this highly complex connection. Variations of these characters, however, always find their measure in the general phasic law. Therefore, to seek the law governing these characters outside of the organism's phases of development, to deduce them straight from the genotype (as the formal geneticists do) or from external factors (as the mechanists of the "mechanics of development" do) means completely disregarding the immediate basis of the laws governing the formation of characters.

Is it possible, for example, to ascertain the law governing the development of such economically important characters as the "vegetative period," "winter habit," and "spring habit," and accordingly to control their formation in a variety not on the basis of phases, but by deduction straight from the genotype? Notwithstanding all reservations concerning the "norm of reaction," which varies in different environments, it is impossible to understand the law governing the period of vegetation of any given variety without a prior phasic analysis.

The usual genetic methods may, perhaps, reveal that the vegetative period of a given variety is different when sown in different localities. But how are we to explain the presence of this difference in some and its absence in other cases of plants sown in different environments, and, in accordance with this, how are we to control the vegetative period? The usual genetic methods are powerless to explain this. At best, these methods can help us only to certify the presence or absence of such a difference (in the [75] norm of reaction), but they cannot help us to foresee the limits of this "norm," or the pattern of the "norm of reaction" of the genotype under different conditions, to forecast this pattern before the seeds are sown at any given point on the map. It is not surprising that, notwithstanding the immense wealth of knowledge accumulated by present-day genetics, varieties are still divided into "winter" and "spring" forms irrespective of the conditions of individual development of the genotype. At the same time the ordinary phenotypical indices of "spring habit" and "winter habit" are projected into the genotype, although different genotypes are merely different foundations for the development of spring habit and winter habit under definite conditions.

If, however, we understand that the characters "vegetative period," "spring habit" and "winter habit" are directly based on phases of development, we are able to really foresee the pattern of a variety's vegetative period under various conditions (to foresee the "norm of reaction" of the genotype). We are likewise able to control this period on the basis of a preliminary analysis of the conditions of existence of the phases of development, by directing the development of the hereditary foundation now along the channel of "spring habit," and now along the channel of "winter habit" (Figs. 25 and 26).

Today it is possible, and necessary, to speak of the plant organism's phases of development as the immediate basis for the development of numerous economically important characters. Passage through a given phase of development does not by itself guarantee the appearance of particular organs and characters, because both organs and characters, which develop on the basis of phases, are limited, like the latter, by their own conditions of existence. But if a plant does not go through a given phase, the very basis for the formation of organs and characters corresponding to that basis fails to come into existence, and the presence of the "external conditions of existence" of these organs and characters will not help to form them. Thus, if a plant is not [76] given the conditions of existence of the vernalization and photo phases, there will be no flowering or earing nor any development of the corresponding characters. The development of the size and weight of the grain may be different, depending on the time the plants pass through their phases. For example, in 1933 the absolute weight of the grains of the wheat Girka 0274, developed under Odessa conditions, was 17.8 gr. The grains from a Girka 0274 sown in the same field and on the same day as those previously mentioned, but which had passed the photo phase quicker (thanks to additional light provided after sunset) had an absolute. weight of 28 gr. The colour and shape of grains also depend on the time the plant passes through its phases.


Fig: 26. Millet
The plant does or does not form panicles, depending on the course of the photo phase of development. On the left is a sheaf grown from ordinary seeds. On the right is a sheaf grown from seeds which had undergone five days' treatment before sowing. The plants were grown under long-day conditions

The characters "farinaceousness" and "vitreousness" are also by no means predetermined entirely in the genotype, but develop in the field in different ways if the course of the phases is different. Immunity and nonimmunity [77] to fungi will likewise be different if the phases take a different course.

The character "frost hardiness" has been studied by geneticists and especially by many plant breeders. But no guidance to action can be obtained in this matter from the ordinary genetic analysis. No matter what analysis the chromosome set may be subjected to, it will not reveal the causes of plants' resistance or nonresistance to frost. From the standpoint of the theory of plant development, however, it was possible to foretell that the character "frost resistance" is also based on the differences in the natures of plants' developmental phases. (Lysenko's paper read at the All Union Conference on Winter Hardiness in 1933.)

On the basis of this forecast a number of investigators (Kuperman, Saltykovsky, Timofeyeva, Melnik) conducted extensive work and the soundness of the proposition was proved.

1The changes in the structure of the hereditary foundation (mutation), i.e., the changes in the ancestral basis, must be distinguished from the individual development of a given hereditary foundation, as being the reproduction in offspring of biological form-building processes similar to, but by no means identical with, those that took place in ancestors. The distinction laid down by Weismann, de Vries and others, between "inherited" and "acquired" characters must be purged of its metaphysical interpretation. Some of the changes that take place in the organism are hereditarily significant for future generations and some are not, but there is not a single purely "inherited" or purely "acquired" character. Every character is the result of a concrete path of individual development of the ancestral basis (hereditary foundation).

From all this it follows that genes, and the genotype as a whole, are by no means the direct cause of the concrete way in which the different characters are formed. Only if uniform conditions are maintained in the laboratory, where so-called "other equal conditions" can be eliminated is it possible to establish the correlation between "genes" and "characters" (which geneticists succeed in doing in a number of cases). If, however, the genotype is, so to speak, carried out to the field (when the seeds are sown), not a trace of these "other equal conditions" is left. Here, one must know the specific role these field conditions play in the development of the genotype. When that is known, it becomes clear that the nature of a given character is directly determined by the concrete course of the phases, or stages, of development, under the definite conditions of existence of these characters. Moreover, the action of most diverse factors not required by the cycle of development inevitably intrudes here and only the whole of this chain moulds the given concrete characters. The genotype is merely the inherited general foundation of the development of the species, variety, etc., which determines the general direction of a plant's development and the character of its varietal requirements of conditions of existence; it does not predetermine the concrete nature of characters. The hereditary foundation is the ancestral basis, which is relatively conservative and within definite limits preserves its specific structure.1 But it itself undergoes development [78] in the course of the plant's individual life, developing through phases and stages into the plant's characters.

The important thing for the practical plant breeder is neither the genotype as such nor phases as such, but characters; however to the latter, and, consequently, to their creation, there is no direct, immediate passage from the genotype. The path from the genotype to the characters runs through the phases of development and the conditions of existence of both the phases and the characters themselves.

Genetic investigations, however, being abstracted from the laws governing the individual development of the genotype into phases, and confined to the search for the "tele-action of the gene," cannot provide a concrete theoretical basis for plant-breeding work.

It is precisely on the established facts of such an absolutely definite sequence of connections in the development of the hereditary foundation into phases, and of the latter into organs and characters, that the work of the Institute of Selection and Genetics (Odessa) is based.

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