THEORETICAL BASIS OF OUR RESEARSHES

THEORETICAL BASIS OF OUR RESEARSHES

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B.S. Kurlovich, S.I. Repyev and L.T. Kartuzova

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Theoretically, our research is founded on the works of Prof. N.I.Vavilov. Nikolai I. Vavilov is recognized as the foremost plant geographer, botanist and geneticist of this age. In the early 20th century, the world was yet unaware of the urgent necessity to protect the environments, and scientists thought little about gradual extinction of plant species. In fact, N.I. Vavilov was the first who understood the imperative of intensive plant collecting, studying and preservation, in spite of the hardest times he experienced in his life. In order to explore the major agricultural regions over the world, Vavilov organized and took part in over 100 collecting missions. During these expeditions, he always focused special attention on leguminous crops in general, and to lupin in particular, regarding it as a source of protein and means of increasing of soils fertility (Синская,1991). He considered this problem as the highest priority in biological and agricultural science and in the attempts to develop sustainable agricultural production. Collecting activities of N.I. Vavilov were started in 1916 with his foreign trip to Iran (Hamadan and Khorasan) and Pamir (Shungan, Rushan, Khorog), and never ceased until the end of his life. All expeditions undertaken by Vavilov and his followers were inspired with the idea of learning about the best plant resources of the world and placing them at the disposal of agricultural practice, thus enriching it with new valuable crops or varieties. As a result of these efforts, by 1940 about 200 thousand accessions had been stored in Vavilov’s collection. Such a rich diversity was thoroughly analyzed in various eco-geographic conditions, systematized and preserved. Vavilov’s foresight concerning possibility of quick disappearance of many valuable plant forms under the influence of human activity proved prophetic. Only for the last 20 years, dozens of plant species and forms have vanished from earth, but many species and forms were saved thanks to the collecting efforts of Vavilov and his followers. During our expeditions abroad, we were repeatedly addressed by the scientists of many countries (Brazil, Israel, Portugal, etc.) with requests to supply germplasm samples collected earlier in their countries by N.I. Vavilov. Such need was evoked by the situation when the requested plant forms with many valuable properties did not exist any more in natural or agricultural environments in these countries. Thanks to Vavilov, they were saved only in the collections of VIR, and are now freely available for everybody. In order to know the great diversity of plants, they ought to be systematized and put in order. Therefore, since the first years of its establishment and study, the plant collection has been used as basic material for working out vital laws and regularities of general biological nature, as well as theoretical fundamentals of plant breeding. The concept of global genetic diversity of cultivated plants remained the keystone of Vavilov’s work throughout his whole life. It incorporated a number of major theoretical conclusions, which played an important role in the development of botany, genetics and plant breeding. The law of homologous series in hereditary variation, idea of the species as a system, differential systematic and geographical method of crop research, botanical and geographical aspects of breeding, and the theory of the centers of origin of cultivated plants formed the core of these studies (Вавилов, 1920, 1926, 1935, 1940; Vavilov, 1997). Vavilov’s theory of plant introduction was developed on the basis of studying the earth’s vegetation. He identified a number of areas distinguished by exceptional diversity and richness of plant species and forms (Вавилов, 1965). Over 70 years ago (Vavilov, 1926), he substantiated the selection of five ancient foci of origin of cultural plants from local flora. Later (1935), he introduced additions and amendments to the decoding of these foci and outlined 6 foci and 2 centers of origin of cultivated plants. It is necessary to note that Vavilov always used to analyze his works in a critical way, developing and deepening their main conclusions in his subsequent publication. In 1940 (Вавилов, 1940), as well as in his Five Continents (published for the first time in Russian in 1962, and translated in English in 1997), Vavilov already named seven main primary centers of origin, placing foci within some of them. The Indian and Indo-Malaysian focus earlier described by him was, therefore, attributed to the South Asiatic tropical center (1940), which in 1962 was renamed Tropical. The Asia Minor and the Central Asian foci were attributed to the southwestern Asiatic center, and the South American center (1935) was renamed Andean (Вавилов, 1940, 1962, 1987). Finally, Vavilov offered the following seven centers: Tropical, East Asiatic, Southwestern Asiatic, Mediterranean, Abyssinian, Central American and Andean. Within the limits of some of these centers, specific geographical foci were also distinguished. According to Vavilov, a center of origin of cultural flora is determined by two prerequisite conditions: abundance of plants suitable for domestication in the local flora, and availability of an ancient agricultural civilization. The work on localization of the centers and foci of origin of cultivated plants was continued by Sinskaya (Синская, 1969), Zhukovsky (Жуковский, 1971), and other scientists from many countries. Sinskaja (1969), in her efforts to expand geographical connections and reciprocal interaction of cultural florae, suggested a broader notion of a historical-geographic area. She identified five areas and considerably updated the list of cultivated crops in each area. Zhukovsky (1971) accepted the theory of Vavilov’s centers, but increased their number to 12 and named them gene centers.

Fig. 2.  N.I. Vavilov’s centers of origin of cultivated plants (Вавилов, 1962, 1987a).

I –  The Tropical center, II – The East Asiatic center, III – The Southwest Asiatic center, IV – The Mediterranean center, V – Abyssinia, VI – The Central American center, VII – The Andean center.

In our opinion (Kurlovich, 1998), there are centers of formation of wild plant species in the places of their origin after the last ice age, and also centers of origin (diversity) of cultivated plants in the places of their introduction into cultivation practice (domestication). Among the supporters of the existence of N.I. Vavilov’s centers there are many scientists from different countries (Kurth, 1957; Harris, 1967; Harlan, 1971; Брежнев and Коровина, 1981; Mathon, 1981). Some critics argue that it is very difficult to determine the very first geographical origin of a species. With this in view, they consider as more proper the term “centers of diversity” in lieu of Vavilov’s “centers of origin”. The term “centers of diversity” is regarded as a safer one (Pistorius, 1997). Thus, Vavilov’s theory of the centers of origin or diversity of cultivated plants has constantly been updated, improved, and even, in some respects, criticized, but it is nevertheless still used as a theoretical basis for collecting, study and utilization of crop genetic resources. So far as lupin is concerned, Vavilov considered the Mediterranean region and mountainous areas of Mexico, Peru and others American countries as native lands for this genus (Вавилов, 1926). Reviews performed on the basis of the approach offered by Vavilov helped to attain more precision in identifying centers of formation and origin for separate lupin species (L. albus L., L. luteus L. and L. angustifolius L.). Their centers were determined by applying the criterion of the greatest diversity of forms in a definite locality with primitive dominant characters. Distribution of lupins as crop plants also resulted in formation of their secondary centers in the areas of intensive cultivation. These findings made it possible to specify places of primary importance for collecting missions and obtain lupin samples valuable for future breeding for resistance to diseases, unfavorable conditions of cultivation, etc. Any plant species when studied in a wide range of geographical conditions, involving inbreeding, segregates into a wide range of hereditary forms, which is difficult to comprehend at first sight. Yet, in studying intraspecific diversity one can observe certain regularities and reveal similarities in accordance with to N.I. Vavilov’s law of homologous series in hereditary variation. The essence of this law may be described as follows. Species and genera more or less closely related to each other manifest similar series of variability lined up with such regularity that, knowing the succession of varieties in one species, one could forecast the existence of similar forms in other species or genera. The closer is the alliance between the species or genera within the general system, the more complete is their similarity in the series of variation. Whole plant families are in general characterized by a definite cycle of variability, which goes similarly through all genera and species of a given family. The laws discovered Vavilov help to put in order extensive materials of cultivated and wild vegetation. N.I. Vavilov marked out the congruity of variability in his description of the whole family of Fabaceae Lindl. The tables with the data and figures on this section are here. Proceeding from the study of separate genera within this family, he established the laws of their differentiation into varieties observable in the sets of characters displayed in seed, fruit, flowers, and vegetative organs. He provided detailed analysis of the variability of characters in the representatives of sections Vicieae, Trifolieae, Loteae, Galegae and Phaseoleae (Вавилов, 1920; 1987). It is clearly visible from his materials that, in spite of the differences existing between the above-mentioned sections, they demonstrate similar variability of characters, mandatory for all genera of the family. Although he presented no data as for the genus Lupinus L., subsequent investigations have shown, that Lupinus illustrates Vavilov’s law of homologous series in variation even better than any other genus of the Leguminosae family. Thus, conducting regular studies of the major lupin species one can observe not only immense diversity in many thousands of plant forms, but also parallel series even in pathological, mutagene and hybrid variability of a given plant. Describing the materials supporting his law of homologous series in hereditary variation, Vavilov paid considerable attention to the feature of plant color. Since various coloring of plants is an approved hereditary character transferred from generation to generation, it was introduced into systematic at a distinctive characteristic of separate species, varieties, subvarieties and smaller taxonomic units. Presently available data show that lupin has a correlation between the colors of seed, inflorescence, carina’s edge, and vegetative parts. These factors facilitate the task of making up intra - and interspecific systematics of plants (Вавилов, 1935). Combination of the coloring of seed, vegetative parts, inflorescence and carina’s edge in various species of lupin from both hemispheres, and complete parallelism in their age variability and in morphological and biological characters doubtlessly witness to their genetic closeness. Application of the above-mentioned laws allowed us to locate and describe several new forms so far unknown in different lupin species, and develop their intraspecific classification. The law of homologous series in hereditary variation gives an answer to the question what material should be looked for, while the theory of the centers of origin of cultivated plants provides an answer to the question where it could be found. To study intraspecific diversity and to determine the centers of origin of cultivated plants, Vavilov and his followers used a differential systematic and geographical method of crop studies (Вавилов, 1931), which meant as follows: · differentiation of a genus into species and intraspecific diversity with the help of morphological, hybridlogical, cytological and others methods; · determination of the genotypic composition of a species; · geographical localization of hereditary forms of a species as well as the centers of their diversity. Of great theoretical and practical importance and subject to further development is Vavilov’s concept of the species as a system (Вавилов, 1931,1965a). Previously, in the science prevailed the notion of Acad. Komarov about monotypic species. According to it, the species cannot include any systematic units of a lower rank (Комаров, 1931,1944). Also widely known was the concept of biological species which postulated impossibility of crossing between species (Grant, 1981,1984). Vavilov made a presentation of one of his fundamental concepts "Linnaean Species as a System". Practical study of several hundreds of species showed the absence of monotypic species, i.e. the species represented by one certain race alone or a certain form alone.

Each species appeared to incorporate a larger or smaller number of forms (genotypes). Vavilov regarded a species as a flexible isolated complex morpho-physiological system linked in its genesis to a certain environment and area of distribution (Вавилов, 1931, 1965a). The research on several hundreds of cultivated species performed by a great number of scientists according to a strictly regulated program lead him to the understanding of the Linnaean species as a definite complex system, i.e. an integrity consisting of closely interlinked components, where the whole and the parts are merged with each other (Вавилов, 1965a, Агаев, 1987, Коровина, 1987). Therefore, in the study of species on the basis of Vavilov’s theories (concept of the species as a system, and differential systematic and geographical method of crop studies) attention was focused not only on morphological characters, but also on geographical and ecological differentiation and other properties of plants. Such approach supported by the development of different intraspecific classifications helped to accomplish profound and comprehensive analysis of intraspecific and varietal diversity of cultivated plants, and find ways of efficient utilization. In this respect, the International Code of botanical nomenclature fixed such categories as subspecies (subspecies), varieties (varietas), subvarieties (subvarietas) and form (forma).

Besides, Vavilov gave special heed to eco-geographical differentiation of the species into ecotypes, geotypes, concultivars, etc. (Вавилов, 1931, 1965a). The postulate of the species as a complex multilateral phenomenon would urge a researcher to use diverse methods for identifying differences between intraspecific categories. In addition to the main morphological method, the scientists of the Vavilov Institute have widely used anatomic, cytological, caryological, paleobotanical, ontogenetic, biochemical, physiological, geographical, genetic and other methods. Such comprehensive approach is especially efficient when the intraspecific diversity of cultivated lupin forms is concerned. This Vavilov’s differential systematic and geographical method of crop studies is interconnected with other findings of N.I. Vavilov and is based on his law of homologous series in hereditary variation, his theory of the centers of origin (diversity) of cultivated plants, and his concept of the species as a system (Вавилов, 1920, 1926, 1935, 1987b). All Vavilov’s fundamental ideas interconnected among themselves and represent a complex doctrine about global genetic diversity of cultivated plants. On the basis of this doctrine, the experts of VIR have developed intraspecific classifications practically for all leguminous crops, including peas (Говоров, 1937; Макашева, 1979), mung bean (Попова, 1937), soybean (Корсаков, 1971, Теплякова, 1997), chickpea (Сеферова, 1997), and vetch (Станкевич and Репьев, 1999). These classifications make it possible to disclose completely the potential of leguminous crops, and they are widely used in breeding practice and plant science. We have also reviewed the system of Lupinus L. using Vavilov’s concept of the species as a system, and applied his differential systematic and geographical method in our studies. On this basis, we offer intraspecific and eco-geographical classifications for three cultivated annual species of lupin (L. albus L., L. luteus L. and L. angustifolius L.). This approach provided a possibility to perform a targeted search of genetic resources of lupins to solve problems of their evolution and selection. It enabled us not only to cast light on the diversity of lupin forms, but also to reveal a series of regularities in their variation depending on the degree of cultivation, geographic environments and soil conditions. Such outcome, in its turn, helped in finding and recommending valuable initial material for breeding. N.I. Vavilov laid a foundation of the lupin collection in VIR. Valuable accessions of white lupin (Lupinus albus L.) were collected by Vavilov during his trip to the Mediterranean in 1926. In Palestine, he managed to find very early, thermally neutral and small-seeded forms relating to the Jordanian ecotype. In particular, the duration of growing period of the sample Tel Karam (k-290) in the conditions of the Ukraine was only 105 days. From Sudan Vavilov brought, on the contrary, very late, but highly productive and large-seeded forms belonging to the Sudanese ecotype (k-486, k-495). Of special value as sources for lupin breeding in Russia, Poland and the Ukraine were samples of the Jordanian ecotype from Palestine. Their hybridization with samples of the Georgian ecotype, and also their involvement in combinations with application of mutagenesis, allowed V.I. Golovchenko to create early and high productive cultivars of white lupin, Kievsky mutant, Horizont and Druzba, suitable for the condition of Russia and the Ukraine (Головченко et al, 1984).

Not only did Vavilov collect and organize studying of the assembled plant materials, but also he constantly strove to improve methods of these studies. He took the initiative, in particular, to develop a simpler and more widely accessible method of determining alkaloids in lupin. This effort of his was inspired by the fact that the technique of detecting and determination of lupin forms with low alkaloid content elaborated in 1928-1929 by v. Sengbusch in Germany was kept secret, since sweet strains of lupin were sold to a private firm. As a result, under the leadership of Prof. N.N. Ivanov, M.I. Smirnova and other experts of VIR worked out an efficient rapid method for determination of alkaloids by means of different chemical reagents. It was immediately published for the first time in the world with the Introduction by N.I Vavilov (Иванов et al., 1932). This publication, together with the know-how of German scientists, launched the breeding work with fodder (sweet) low-alkaloid lupin on a worldwide scale. Numerous scientists in many countries continue the traditions and methods of Vavilov. On the field of cultivated crops, especially legumes, ideas of Vavilov have been further developed in Australia (Gladstones, 1974, 1998; Sweetingham, 1986, 1989; Cowling, 1994; Clements and Cowling, 1990, 1991), Finland (Hovinen, 1994; Tigerstedt, 1994), Germany (Diederichsen and Hammer, 1996), Italy (Laghetti et al., 1996; Saccardo, 1996), Poland (Swęcicki W, 1988; Swęcicki W.K., 1996; Kazimierski and Kazimierska, 1992; 1994), Portugal (Mota, 1984; Gusmão, 1988 ; Gusmão et al., 1996; Tavares de Sousa et al., 1992; Neves Martins; 1994; Dordio, 1996), Sweden (Blixt, 1970, 1996), UK (Polhill, 1976, Bisby, 1981; Ambrose, 1996) and many others.

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N.I. Vavilov symbolizes the glory of Russian and world science and, at the same time, personifies its tragedy. In the stifling atmosphere of Stalin’s totalitarian rule, the Institute of Plant Industry headed by Vavilov turned into a bulwark of resistance against the pseudoscientific ideas of Lysenko. Because of this controversy, Vavilov was arrested and died in prison in 1943. Nevertheless, the memory of Nikolai Vavilov was honored by his followers, and preserved in his collections of plant genetic resources, ideas and books. This priceless heritage of Vavilov not long ago was chronicled in his posthumous book Five Continents (Вавилов, 1962, 1987a, Vavilov, 1997). Scientific accomplishments presented further in this publication represent physical realization of Vavilov’s ideas with reference to lupin. More than 2500 accessions of lupin stored in the collection founded by Vavilov were used as materials for our research!