T. D. Lysenko
CAUSES OF THE DEGENERATION OF POTATO PLANTING MATERIAL IN THE SOUTH
Under the conditions prevailing in the South where the summers are hot the potato fares badly. It quickly loses its nature, its fine hereditary qualities.
The first year of planting, with good agrotechnique, a fairly good crop (10-15 tons per ha.) will be obtained from sowing material brought from the North. But if you take tubers from this crop and plant them the next year again in the same southern area, the new crop, as a rule, will be considerably smaller than the preceding one. If you plant material grown twice in the South (in two generations) the crop will drop to half or a third. When early varieties of potatoes were reproduced three or four years in the South (and in the South alone could they be cultivated) things reached such a pass that from a ton or somewhat over a ton of seed potatoes per hectare used in spring a harvest of somewhat less than a ton would be received, i.e., the crop would not even return the planting material expended. In practical farming this behaviour of potatoes in areas where the summers are hot was termed degeneration.
In order to maintain potato growing in the South, planting material had to be brought in annually from the more northern or the upland districts.
Before the revolution planned deliveries of planting material to the South were not feasible. For that reason the potato was almost unknown in the steppes of the Ukraine and the Northern Caucasus as well as in the cotton regions of Central Asia and the Transcaucasian republics. The urban food supply of potatoes was brought in from the North or the upland districts.
In our time, after the October Revolution, seed potatoes began to be delivered to the southern regions every year. But it was rather difficult to develop potato growing to any considerable extent in these regions by the use of outside seed material.
The rapid decline of southern potato crops when planting tubers bred under southern conditions was attributed by the old scientists to disease and not to a change in the nature (heredity) of the potato. For to admit a change in the nature of the potato when cultivated in the South would mean to admit a change in the heredity of an organism due to conditions of life, and it was not to the advantage of the bourgeois science of heredity to admit such a dependence. It does not recognize it to this day.
The swift and readily detected change in the behaviour of potato varieties when reproduced in the South was called by scientists a specific southern potato disease. But since the pathogenic, i.e., the contagious, element could not be discovered, this disease was included' among the diseases caused by filterable viruses, and virus diseases are known to be infectious. In this connection it was the established rule that in the South seed potatoes were not to be planted at a distance of less than two or three kilometres from virus-infected potatoes, regardless of the percentage of infection.
Every year carloads of good planting material were brought to seed-potato farms in the South from the northern regions. It was planted in isolation, far away from degenerate potato fields. But there was not a single case of a seed-potato farm in the South producing even one ton of good, sound planting material for farms growing potatoes for consumption. Sound potatoes brought in from the North degenerated in the course of one or two years during the process of reproduction.
Little success attended also the efforts of plant breeders in the southern regions who for decades tried to produce a variety of potato that would resist degeneration, resist the so-called virus diseases.
True, by sowing seeds instead of tubers, plant breeders quite easily, succeeded in obtaining tubers which when sown the following year produced a crop qualitatively and quantitatively superior to that of any variety brought in from the North. But three or, four years later, when this new, variety (new strain) had increased to, say, 20-30 c., it usually proved to be already degenerating and yielding small crops.
Today it can be said with certainty that people in the South suffered reverses in their efforts to grow potatoes because the accepted "scientific" explanation of the degeneration of potatoes in the South was incorrect, was at variance with the facts. Scientists did not approach the potato from the angle of the interrelation of the organism and its environment. This was the basic mistake of science in explaining the question of potato degeneration in the South.
When in our research work we decide particular questions of agrobiology we begin, as a rule, with an analysis of the interrelations of the given organisms with the environment that surrounds them. Such an analysis must, of course, not fail to take into account the various diseases and the conditions under which they develop.
Let us try, as far as possible, to recall and briefly recapitulate the course of our argumentation in 1933 when at the Odessa Institute of Selection and Genetics we for the first time undertook to solve the problem of combating potato degeneration in the South.
How are we to explain the fact that potatoes shipped south, for instance, from Gorky Region to Odessa Region, yield a good crop the first: year but a considerably smaller crop the second year? Why, from what external causes does planting material deteriorate after reproduction in the South? After all, the preceding year, when it was brought south from the more northern regions, its breed qualities, i.e., its seed qualities, were good. It follows that here in the South, certain conditions must exist which differ from conditions elsewhere and which rapidly deteriorate the breed qualities of the potato, its seed qualities.
At first the idea may occur to one's mind that the length of the day is to blame. For in summer the days are shorter in our southern districts than in the northern districts, and scientists know that the length of the day frequently plays no small part in the development of plant organisms. One need only compare the results obtained by growing, for instance, certain varieties of millet under conditions of different lengths of the day for different plant behaviours to be easily observed. Plants which at the inception of their development were given even only 10 short days of 10-12 hours each (and correspondingly long nights) sharply reduced their vegetative period.
But the supposition that the length of the day has any bearing on the change in the property of the potato we are discussing must be rejected. In any district of the South the potato develops splendidly and does not deteriorate in breed if planted on foothills or in the uplands. Contrariwise, potatoes degenerate in the South if planted in valleys where the day lasts about as long as in the mountains. Hence, the length of the day is not a cause of the potato's degeneration.
|1However, generally speaking, in a plant organism everything depends on food, in its wider sense, on metabolism, on the interconnection with the environment.|
Again one might assume that the soil was the most important factor in the degeneration phenomenon. We know that in the South the potato thrives better in vegetable gardens near brooks or on sandy soils, and there holds out somewhat longer, i.e., its degeneration is slighter than in the ordinary soils of fields. Yet in the more northern and upland regions with their diversity of soils the potato does not deteriorate as it does in hot regions. Hence it is clear that neither the soil nor, consequently, the nutriment of the plants in the direct sense was the chief cause of the degeneration of the potato.1
Only environmental differences in temperature explained, and that quite easily, why in the extreme South, for instance, in the Azerbaijan Soviet Socialist Republic, the potato could not hold out more than a year in the valleys, whereas 30-40 km. away, in the foothills and upland districts, it grew better than in the more northern districts, for instance, in the Ukraine (before the introduction of summer planting there).
It would be incorrect to assume that a high temperature has a bad effect on the potato plant during the entire process of its development. High temperatures occur alike in Moscow Region and in the southern highlands during certain periods of the potato's vegetation, yet, as is known, the potato grows well in these localities. Consequently, a high temperature does not run counter to the numerous biological requirements of the potato. It is therefore not at all a question of the action of high temperatures on all processes of development of the potato plant but a question of the action of high temperatures at particular moments in the development of its separate organs. The fairly large number of experiments performed by that time in the domain of what is known as the phasic development of plant organisms helped us to find our bearings in this question.
At that time we already knew that if you take, for instance, a seed-grown annual plant which can be propagated by cuttings, cut up its stem lengthwise and root the cuttings under identical conditions, it will be readily observed that plants derived from cuttings taken from the crown and a little below it will, as a rule, produce flowers earlier than plants derived from cuttings taken from the part of the stem near the roots. The latter cuttings will flower almost simultaneously with plants obtained from seeds sown when the cuttings were rooted. Plants obtained from cuttings near the stem's roots prove to be as young, as near to the commencement of individual life and as far from its end as organisms which start life from the seed. Conversely, cuttings taken from the top, i.e., above the part of the stem where there have been buds or flowers, yield buds and flowers early. Annual plants grown from such cuttings are at the very beginning near the end of their individual lives, near the formation of seeds.
Hence, we arrived at the conclusion that the cell tissue along the stem of a plant organism is qualitatively heterogeneous in the sense of phasic development, in the sense of the stages of individual life of the organism.
The older in growth a tissue is (the lower down the stem, i.e., the nearer the root it is), the younger is it in development, the more ways remain for the various complicated and largely still unstudied transformations and modifications through which plant organisms normally pass before completing their lives.
Conversely, the nearer to the top of the plant the cell tissue is—it usually is the youngest tissue—the fewer possibilities there are for vital transformations. The individual life, the general cycle of development, approaches its normal end, old age. When a plant starts from the seed, life begins anew (with a repetition of the phasic stages). In cases of propagation by cutting, tuber, etc., the life of the organism does not begin de novo. It is in direct form a continuation of the life of the previous organism, or, to be more exact, of the cell tissue which was taken for propagation.
This gave rise to the thought that the rapid degeneration of the potato in the South is, basically, a result of the phasic aging of the potato as a flowering seed plant. But how can this be proved?
In 1933 E. P. Melnik, a researcher of the Institute of Selection and Genetics, at our suggestion prepared cuttings from Ella variety potato stems. These cuttings produced plants which yielded tubers. The tubers were picked and kept until the spring of 1934, when they were planted. It was found that the tubers which in the experiment came from upper-stem cuttings produced approximately half as big a crop as the tubers derived from cuttings taken at the base of the stem, i.e., from the place where tubers usually form under the ground. The former yielded an average crop of 120 gr. per plant, the latter—250 gr. Tubers from top cuttings produced potato plants similar in appearance to those which in the South are called degenerated, while tubers from cuttings taken from the lowest parts of the stalk produced considerably better plants.
We now began to understand why the potato, a flowering annual plant, propagated year after year not by seeds but by tubers, in many localities neither degenerates nor ages in decades. The explanation is that year after year the tubers get their start from the phasically youngest cells, from cells of the lower, underground part of the stem. By that time it had already been ascertained that phasic changes in seed plants take place in the cells of the growing points of stems.
It was assumed that if high temperatures act sufficiently upon the germinating eyes of the tubers, i.e., on the growing points of the future stems, the tissue of these eyes will become decrepit and the tubers having such eyes will, when planted, yield degenerated plants. The stems will originate from decrepit eye tissue. The new tubers will likewise develop from decrepit tissue and therefore will possess little vitality, will be degenerate.
This phenomenon was tested experimentally in the following manner. Absolutely healthy, undegenerated tubers were taken and cut in half. Some of these halves were placed in a basement, the others in a thermostat at a temperature of 30°-40°C. and kept under these conditions for 25-30 days. Then they planted all the halves (from both the basement and the thermostat). The potato plants obtained from the basement halves were healthy while the thermostat halves were suffering from the southern disease.
When early-maturing varieties of potatoes are cultivated in hot southern districts the eyes on newly-formed tubers frequently begin to sprout even before the crop is picked. On the basis of all this it was assumed that the action of high temperatures on even slightly stimulated eyes, eyes which had just about started to sprout, was the principal cause of the rapid mass degeneration of potato planting material in the South.
Such, briefly, was the line of reasoning and the minor experimentation which in 1933 and 1934 enabled us to ascertain why potatoes quickly degenerate in the South and to map out the course to be taken in order to combat this phenomenon.
The question arose of what to do to prevent high temperatures from affecting the eyes of tubers of one year's crop intended to be used as planting material for the following year's crop.
Let the high temperatures act on the stems and foliage of the potato plant. The higher (to a certain extent) the temperature the faster is the progress of the life of the potato plant, the formation of the crop, the normal aging of the stem and leaves. All this constitutes the normal course of life of the potato plant. Only do not let the decrepit, aged parts be used the following spring as the basis for the new offspring, for planting purposes. High temperatures must not be allowed to affect for any great length of time the stimulated eyes of tubers from which the new plants will begin to grow after the planting.
Thus originated the idea, in 1933, of trying to plant seed potatoes in summer instead of in spring, so that the tubers might develop in the cooler autumn weather. On the other hand, since the young tubers obtained from such a crop would not be ripe by harvest time and would therefore fail for a long time to stimulate the sprouting of their eyes, they would not, in winter, be subject to aging or decrepitude under the rather warm conditions of the South. It has already been ascertained that as long as the eyes of the tubers are not stimulated to sprout they cannot be affected by high temperatures in the sense of changing the nature of the potato.
SUMMER PLANTING TESTS AT THE INSTITUTE OF SELECTION AND GENETICS AND ON COLLECTIVE FARMS
On July 6, 1933, at the Odessa Institute of Selection and Genetics, 0.25 ha. of land were planted with potatoes of the Ella variety after a crop of young potatoes had been gathered in that field early in the spring. The summer was rainy that year. The Institute therefore succeeded in obtaining potato sprouts on a section where one crop had already been raised, which in ordinary years cannot be done under southern conditions on unirrigated plots.
In the autumn the July planting of 0.25 ha. yielded approximately 2.5 tons of potatoes. The tubers of this crop weighed the usual 100-150 gr. on the average.
In the spring of 1934, 1.5 ha. were planted with tubers from the summer-planted potatoes. Part of the tubers were left for a second planting in the summer of 1934. Alongside of the potatoes planted in spring from the crop yielded by the summer planting were planted tubers of the Ella variety obtained from normal, spring-planted crop. It was difficult to detect any difference between these two plantations; nothing in particular distinguished the behaviour of the plants obtained from the tubers of summer-planted crop. When I recall the behaviour in 1934 of the plants obtained from the tubers of the first summer planting in 1933 I believe hardly anybody could have anticipated how effective, in the sense of improving the planting material, summer plantings would subsequently he under southern conditions.
One might think the behaviour of the plants in the above experiment of planting in the spring of 1934 tubers obtained from Ella plantations of the preceding summer and spring did not bear out our above-expounded assumption that summer plantings would stop the deterioration of potato planting material when reproduced in the South. It is difficult to say today whether in view of the results of this first experiment we would have ventured to propose that the collective farms plant potatoes in summer. I think we would have. What actually happened was the following. In the winter of 1933-34, i.e., before the above experiment was performed for the purpose of testing the seed quality of the planting material obtained from the 1933 summer plantation, A. D. Rodionov, a specialist of the Institute of Selection and Genetics (now its director), ordered a carload each of potatoes of the Epicure and the Early Rose varieties to be shipped from Gorky Region to 16 Odessa district collective farms for the purpose of testing the idea of planting potatoes in summer.
To plant potatoes in summer under the conditions of the arid south of the Ukrainian S.S.R. on unirrigated land necessitates the careful retention of the winter and spring moisture in the soil. To this end it was suggested to the collective farms that they leave the autumn-ploughed sections untilled and in early spring begin to till them in the way good bare fallow is tilled under the conditions obtaining in arid districts. The planting was done at the end of June, i.e., when the grain was being harvested. The summer of 1934 (particularly the first half) was hot and exceedingly dry. Many collective-farm members, men and women, as well as a number of agronomists, looked upon the proposal to sow potatoes in summer with distrust. That was quite a normal reaction. In these regions potatoes, as we have already stated, had been faring rather poorly even when planted early in spring. To plant them at the driest and hottest time of the year, when gathering in the grain, seemed of course impractical and uncalled for. Owing to the distrustful attitude to this proposition the collective-farm experimenters, who had undertaken to summer-plant 1-2 ha. of potatoes on each collective farm, encountered great difficulty in securing assistance for the proper preparation of the fields and for the planting. In the autumn, when picking the crop, all the doubts of the collective-farm members were dissipated. Despite the dry summer the potato tubers obtained from the summer-planted crop were on the whole of a size beyond all precedent in the South—400-500 gr. each. The tubers were considerably bigger than in our first summer-planting experiment, in 1933, which had not been performed on land left fallow since spring, but on a plot on which an early-spring potato crop had already been picked. I shall dwell below on the causes responsible for the considerably greater size of the tubers obtained in 1934 as compared with 1933. I shall only note now that we had not expected an increase in the size of the tubers as a result of the summer planting of potatoes.
Tubers which the collective-farm experimenters obtained from the summer plantings were planted in the spring of 1935 on the same collective farms. Alongside were planted potatoes obtained from the ordinary spring plantings.
The collective farmers performed these experiments not on small plots but on whole hectares, for the practical purpose of obtaining potato crops.
After the appearance of shoots a sharp difference was observed between the plants of the fields on which summer-planted tubers and ordinary spring-planted tubers had respectively been used. The early variety plants (Epicure and Early Rose) obtained from summer-planted tubers of southern reproduction were in no way inferior in vigour and healthiness to the plants of the same varieties obtained from tubers brought in from northern districts in the year they were planted, i.e., in the spring of 1935. Conversely, the plants of these same varieties obtained from tubers that had gone through one year's spring reproduction in the South were weak, degenerate. The fields under summer-planted tubers yielded crops about twice as big as the fields with spring-planted tubers of southern reproduction.
In the spring of the same year (1935) Ella variety potatoes were planted at the Institute of Selection and Genetics to compare the results of the new second-year summer reproduction with those of the ordinary spring reproduction. In 1935 the experiment with the Ella variety, after two years of summer reproduction, also showed good results for material obtained from summer-planted crops. It was found that only 8.8% of the plants obtained from the previous summer planting was degenerate. But the potatoes obtained from the former, spring-planted tubers contained 58.9% of degenerate plants.
How are we to explain the fact that the potatoes from the 1933 summer planting produced no difference in the quality of the planting material when planted in the spring of 1934 and that a difference was found only in 1935?
Today it is quite easy to explain this.
The Ella variety, being a plant of medium maturity, degenerates more slowly when reproduced in the South than early-maturing varieties. The material taken for the experiment was brought to the Institute from Kiev Region in 1931 and in 1933 did not yet have time to degenerate to any considerable extent. The summer of 1933 was cool and rainy. Therefore the spring plantings of that year likewise deteriorated the planting material only a little. As a result, in the spring planting of 1934 the plants derived from former summer- and spring-planted tubers proved to be almost alike.
At that time we suggested the summer-planting method for the sole purpose of stopping the degeneration of potato planting material in the South. We had as yet no idea of what is now well known to us, namely, that seed potatoes can be improved by summer planting.
Different results were obtained in experimenting with summer planting in 1934. It was a hot and dry year, particularly, as has already been stated, during the first half of the summer. Under these conditions the potato crop obtained from the spring planting showed great degeneration. But when planted in summer the potatoes not only did not degenerate or deteriorate but exhibited considerable improvement compared with what they had been when brought from the North.
In order to show how much better summer-planted seed potatoes are than those spring-planted under southern conditions I shall refer to an experiment performed by A. F. Kotov, a specialist of the Odessa Institute of Selection and Genetics.
In the autumn of 1935 he selected 300 of the best plants from the Early Rose summer-planted potato section. He did not mix the tubers taken from these plants but stored them separate in a basement till the spring of 1936 when half of the tubers obtained from each plant were planted in the field and half were left in the basement till the end of June. The latter were then planted in the field in beds alongside of the early-spring plantations. The beds were so arranged that the progeny of the tubers of each summer-planted plant, picked out in the autumn of 1935, grew next to the spring-planted progeny of the same plant. The total crop was harvested in the autumn, simultaneously. Until the summer planting the field had been kept in a clean friable state.
It could readily be noted that in the progeny of every plant selected in the autumn of 1935 the crop from the summer planting was bigger than from the spring planting. The tubers of the summer-planted part of the crop were several times as big as the tubers of the spring planting. The crop picked from each clone (the progeny of the separate plants) of the summer as well as the spring plantings was kept separately in a basement. In the spring of 1937 about half the tubers from the crop of the preceding year, both of the spring and the summer plantings of each clone, were planted for the purpose of comparing the quality of the seed potatoes obtained from the former spring and the former summer planting. The other half of the tubers from each clone was left for planting in summer. On the whole 4 variants were obtained from the progeny of each plant selected in 1935:
|1See present volume, pp. 202-04—Ed.|
On examining the spring plantings of this experiment it became strikingly apparent that the plots of all the clones planted with tubers from the previous summer plantations were superior to the plots planted with tubers obtained from the previous spring plantings. I have already published the results of this experiment ("Collective-Farm Laboratories and Agronomic Science," in the journal Yarovizatsia, No. 5, 1937).1 I shall therefore not deal with them in detail. I shall only point out that the crops of plants derived from tubers of prior summer planting are in many cases two or three times as big, and even more, as the crops picked from plants obtained from prior spring plantings. Thus, for instance, clone No. 59 from tubers spring-planted in 1936 on being spring-planted in 1937 produced an average crop of 153 gr. per plant. Tubers of the same clone planted in the spring of 1937 alongside of the tubers mentioned above but which in 1936 had been obtained from a crop planted in summer and not in spring produced an average crop of 315 gr. per plant instead of 153 gr. Clone No. 232 from tubers spring-planted in 1936 on being planted in the spring of 1937 yielded 80 gr. per plant on the average, whereas the same clone derived from summer-planted tubers produced an average crop of 413 gr. per plant. There was not a single case of a crop of any one of the 300 different clones obtained by planting tubers reproduced in summer being smaller or only equal to the crop from plants derived from tubers of a prior spring planting.
The same results were observed in the variant of the 1937 experiment with summer instead of spring planting, the only difference being that in the case of summer planting a considerably bigger crop was obtained regardless of whether the tubers were planted in spring or in summer the preceding year.
From 1935 on an increasing number of collective farms (at first hundreds, then thousands and tens of thousands) in the southern regions of the Ukrainian S.S.R., and later also in the southern districts of the Russian Federation, began to participate in the practical farming experiment of planting potatoes in summer for the purpose of stopping potato degeneration under southern conditions.
The spring planting of potatoes on collective farms with tubers from crops planted the previous summer strongly influenced the South in favour of planting seed potatoes in summer.
After extensive practical and experimental testing it can be said that our above-mentioned assumption relative to the causes of potato degeneration under the conditions of heat prevailing in the South seemed to have been splendidly confirmed. I say "seemed."
Although the above assumption as to what causes potatoes to degenerate in the South is relatively true (it can be tested experimentally any year) the practical results of summer planting have shown this explanation to be narrow and one-sided. As a matter of fact, it has been palpably plain for several years now that the summer-planting of potatoes in the South is a method not only of stopping the degeneration of potato planting material brought from northern districts for reproduction under the conditions prevailing in the southern districts but a method of considerably improving this planting material. This, after all, does not follow from the above explanation. The entire explanation was built on a divorcement of the individual development (ontogenesis) of plants from the development of the breed (phylogenesis). This mistake, of major importance to science, was easily and quickly discovered in practical farming. The grain of truth in the assumption was made use of by the practical farmers, while practice supplied theory with a splendid series of facts that demonstrated the unity of ontogenesis and phylogenesis.
It was noticed that in the mass, with each new reproduction brought about by summer planting, the tubers increased in size. I shall point out at least the following general observation we made. Whereas in the first year (1934) that potatoes were summer-planted in collective farms tubers weighing 300-500 gr. could be found, in subsequent years some tubers weighed as much as 1 kg. and later 1.5 kg. There were rare cases of their weighing even 2 kg. This alone was sufficient to warrant the conclusion that if potatoes shipped to the South from northern districts are planted in summer, they not only do not deteriorate, do not degenerate, but may even improve the breed, i.e., their seed properties, from year to year.
It turned out that in summer planting the seed qualities of potatoes are as liable to change as in spring planting, however with this essential difference that when planted in spring in the South the potatoes deteriorated, degenerated with each reproduction, but when planted in summer their quality on the contrary improved with each reproduction.
It used to be generally accepted that if planting material of, for instance, the Early Rose variety obtained from Moscow Region crops and planting material of the same variety obtained from Odessa Region crops are planted under comparable conditions, the yield of the Moscow Region planting material will almost always be considerably greater than that of the Odessa Region planting material. Now a multiplicity of experimental data points the other way. Last year, too, in 1940, I. E. Glushchenko (a researcher of the Institute of Genetics, Academy of Sciences of the U.S.S.R.) in his experiments performed on a plot of land near Moscow obtained a potato crop of the Early Rose variety from southern tubers reproduced in summer at the Odessa Institute of Selection and Genetics amounting to 480.5 c. per ha., while under the same conditions the same variety of local origin (the Potato Institute, Moscow Region) produced a crop of 219.5 c. per ha.
All this argues in favour of the proposition that in the South planting potatoes in summer is a method of improving potato breeds and not merely of stopping their degeneration.
While finding a solution for the special and practically important problem we have discussed—the problem of combating the degeneration of seed potatoes under southern conditions—it seems to me there have been clearly revealed a number of regularities which in some measure or other have a bearing on numerous plant and, I think, also animal organisms. Thus, for instance, unimpeachable experimental proof was supplied on small and big plots of summer-planted potatoes in support of one of the most important and fundamental propositions of agrobiological science, which holds, in substance, that the environmental conditions which are conducive to good development of particular organs of plants, for instance potato tubers, also improve the breed of plants in the same direction.
Practice has shown that in the South seed potatoes obtained from summer plantings are considerably better in point of breeding qualities than those secured from spring plantings. That this breed improvement takes place as the result of good environmental conditions during the period of development of summer-planted tubers is borne out by the fact that tubers from summer-planted crops are on the whole considerably bigger than tubers of the same variety derived from plants planted in spring. And it goes without saying that big tubers are obtained as a result of good environmental conditions at the time they develop.
It must also be stressed that the fact that tubers of various sizes are taken for comparative plantings—bigger ones from summer planting and smaller ones from spring planting—is not the reason why the yield of seed potatoes of summer reproduction is considerably higher than that of planting material derived from spring reproduction. In the South, at the Odessa Institute of Selection and Genetics, numerous experiments were made in which the smallest tubers, weighing 10-20 gr.—tubers which fail to develop by the time the autumn frosts set in—were taken from a summer-planted crop to compare breed qualities. These tubers were planted alongside of the considerably bigger ones (50-100 gr.) derived from spring-planted southern crops. Nevertheless the yield of plants from tubers of summer-planted parentage was, as a rule (and in the case of early varieties in the South without exception), considerably higher than the yield of plants from tubers of spring-planted parentage. This goes to show that the breed of potato tubers derived from summer plantings is changing. If planted in summer good conditions are established for the development of potato tubers. Owing to this the tubers obtained are big and at the same time the potato breed is improved, changed in the direction of large-sized tuber production.
The proposition that efficient agrotechnique and zootechnique improve the quality of plant varieties and animal breeds, and that inefficient agrotechnique and zootechnique cause even the existing good plant varieties and animal breeds to deteriorate—a proposition generally recognized in practice and, contrarily, rejected by bourgeois genetics—is thus easily corroborated experimentally. This conception of the breed (heredity) of organisms naturally leads to the following practical conclusion: seed plots must be spared bad agrotechnique since bad agrotechnique deteriorates the breed of plants. Good agrotechnique must be taken to mean the creation of conditions that will facilitate the development of desired qualities and quantities of seed or planting material.
Why do good environmental conditions result in the South if potatoes are planted in summer; why do these conditions cause big potato tubers to develop and at the same time the potato breed to improve? In my opinion this phenomenon is to be explained as follows.
In the arid districts of the South it is absolutely necessary, in order to obtain potato shoots when planting between the end of June and the middle of July, to take a section of land deep-ploughed in autumn, to keep this land from early spring up to the time of planting like the best bare fallow, i.e., clear of weeds and with a loose upper layer of mulch. Under these conditions the supply of winter and spring moisture is well retained. Simultaneously, about the middle of summer, as is shown by the extensive data in possession of experimental stations, a great quantity of soluble nutritive substances accumulates on this land. The accumulation of nutrient nitrates alone amounts to 50-60 poods a ha.
When summer-planted in the South potatoes in a good and properly tilled field enjoy what I should call exceedingly good food conditions. During the latter half of summer—in the beginning of autumn when the temperature is no longer too high and a large quantity of easily assimilated nutritive substances is available—stems and leaves develop luxuriantly and in two or three weeks large tubers begin to develop.
In general we assert even today that the principal cause of potato degeneration in the South under spring planting is the action of high temperatures on the potato eyes that are being stimulated to sprout at the time they are under the vines, or after the harvest while in storage. On the other hand, improvement of planting material derived from summer planting is caused by good food conditions, good conditions for the development of potato tubers.
This explanation makes it intelligible why in the first year of our experiments with the summer planting of potatoes, in 1933, no improvement in the planting material was achieved. I have already said that in comparable plantings in the spring of 1934 we discovered no difference in the behaviour of the plants, whether they were obtained from tubers of the preceding year's spring planting or summer planting.
The medium-maturing Ella variety, when planted in the spring of the cool, rainy year 1933, did not degenerate, nor did summer planting improve its breed, because it was produced on a plot poor in assimilable nutrient substances, on land from which a potato crop planted in early spring had been harvested. This explains the lack of difference in the case adduced between seed potatoes obtained from spring and from summer planting.
The practice of planting potatoes in summer has brought up a question of profound interest to agrobiology: not only the body of an organism but also its nature, its heredity builds itself from food. Many Soviet investigators have substantially confirmed this by experiments, first, with potatoes and then with many other plants. In the given case I have in mind experiments in vegetative hybridization.
In his splendid teaching on mentors I. V. Michurin showed how the nature of plants can be changed by means of grafting. Until quite recently the high priests of science did not want to recognize this. Now when vegetative hybrids have been obtained literally in masses this can no longer be denied.
First published in 1943
It is interesting to compare the above discussion of experiments that preceded the large scale practice of summer-planting with Joravsky's odd claim (The Lysenko Affair, 1986):
"Plant breeders had been told to develop varieties of potatoes immune to the degenerative diseases that inhibited potato growing in regions with hot dry summers and forced upon the overstrained railroads constant shipments of potatoes from north to south. In 1935 Lysenko announced that breeding new varieties was unnecessary. Southern farmers could solve the problem immediately by planting potatoes in the middle of the summer. They would mature in the cool fall, thereby escaping degenerative diseases. With this snap judgement, somehow vaguely connected with his theory of stages, Lysenko fell into conflict with plant pathologists and virologists, who had proved that the degenerative diseases are contagions rather than physiological disorders caused by heat."
The only "proof" that the degeneration was caused by a virus was that no fungus or bacterium could be found. To the contrary, research begun in 1933 had demonstrated that heat did cause degeneration.
Joravsky made another amusing blunder in regards to Lysenko's recommendations on potato culture.
"Far more daringly he announced that potato tubers can be vernalized, though they are not true seed, if they are sprouted in warmth and light. Thus he renamed and advertised as his discovery what was actually an ancient technique of potato growers — sprouting the tubers before planting in order to give the crop a head start. In this case "vernalization" usually does increase yield, if it is done the ordinary way instead of Lysenko's. He urged farmers to string up the seed tubers on wire or cord, which would have increased labor costs and the dangers of infections."
Lysenko, in fact, warned, "High temperatures must not be allowed to affect for any great length of time the stimulated eyes of tubers from which the new plants will begin to grow after the planting."
Chouard (1960) knew that Lysenko recommended low temperatures.
"As an example, chilling potatoes to increase tuber yield, though commonly but wrongly named 'vernalization,' merely utilizes an aftereffect of cold on vegetative vigour and has nothing to do with the specific aim of vernalization which is to induce the capacity for flowering."
Kubicki (1960) also knew about the benefits of low temperatures.
"Vernalization of these [potato] varieties took place under average farm conditions. The tubers were arranged in slat cases 55 x 45 cm to a height of three layers. The cases were stored in such buildings as barns, cattle sheds, pigsties, distilleries. The temperature in these buildings was maintained within a range of 4 to 20 C; daylight was sufficient."
Only poor Joravsky got it backwards.
As for stringing up tubers on wire or cord, this should be understood in the context of a specific project. Lysenko (1943):
"The cutting off, storing and planting of the tops of big food tubers is one of the measures that improve potato breeds and increase their yield. It is therefore extremely necessary at the present time that both scientific workers and agronomists pass on their practical experience in the planting of potato tuber tops, spreading this knowledge as widely as possible so as to ensure the practical application of this measure on a still larger scale in 1944."
One cannot toss the cut off potato tops into a bin and just hope that they do not rot. Hanging them on a cord or wire in a cool dry place until they can be planted is a perfectly reasonable practice.