N.I. Vavilov with his wife E.N. Barulina, 1926 (before their expedition to  the Mediterranean).   E.N. Barulina  was the leading scientist  in the field of genetic resources of Leguminous crops.

This example has become a classic illustration of Vavilov’s law of homologous series in hereditary variability (Sinskaja 1969; Makasheva 1973, 1979; Vavilov 1987a, 1987b). Forms of legumes with various seed and flower colours, obeying the law of homologous series, are demonstrated by many species of lupin, peas, mung bean, string bean and fodder beans. In 1924, Vavilov organized an expedition to Afghanistan together with V.N. Lebedev and D.D. Bukinich (to Herat, Afghan Turkestan, Gaimag, Bamian, Hindu Kush, Ba Kafiristan, Jalalabad, Kabul, Kandahar, Baquia, Helmang, Farakh and Sehistan). The findings from this expedition supported the conclusions about southwest Asia as a centre of origin of many plants. It was established that Afghanistan was a major primary focus of formation where there existed a large diversity of many major Eurasian crops, representing an inexhaustible source of initial material for selection (especially for drought resistance). Following this hazardous and very fruitful expedition to Afghanistan, Vavilov was awarded the N.M. Przevalski Gold Medal of the Russian Geographic Society, of which Vavilov was president from 1931 to 1940.

Vavilov had a special interest in the Khoresm oasis, whose proximity to Afghanistan and Iran supported the hypothesis that this territory was also a focus of formation. Vavilov inspected area around the Amu Darya River (Khiva, Urgench, Gurlen and Tashauz) in 1925. Whereas there were signs in Iran and Afghanistan that cultivated plants had developed locally, Khoresm showed signs of connections with northeast Africa and Egypt that influenced the features of cultivated plants. White-seeded forms of peas, haricot bean and fodder bean were found in Khoresm, together with particular forms of groundnuts and alfalfa. Khoresm oasis was characterized by an abundance of many recessive forms of cultivated plants (Vavilov 1926; Bazilevskaya and Bakhareva 1991).
In 1921 Vavilov organized a trip to Canada (Ontario) and the USA. The official purpose was to search for sources of resistance to drought, necessary for restoring Russian agriculture after a severe drought in 1921. Vavilov understood from his first visit to North America that the continent was not a focus of intensive formation of plants and agriculture (Vavilov 1965b, 1987b). The main foci of plant diversity were to the south, in southern Mexico, and Central and South America. Vavilov visited a number of European countries (Britain, France, Germany, Poland, Holland and Sweden) on his return from America in 1922. As a result of these and his subsequent travels to Germany in 1927, the USA in 1930, Canada and other American countries in 1932-33, he added commercial varieties and a selection of legumes from many countries to the collection of VIR.
Vavilov visited Mediterranean countries in 1926: northern Africa, the islands of Cyprus, Crete, Sicily and Sardinia, and southern Europe (Portugal, Spain, France and Greece). He noted the role of leguminous crops (particularly chickpea) in supplying both people and livestock with protein and as a means of increasing soil fertility (especially lupin) (Vavilov 1997; Loskutov 1999). He found that the activities of people had little effect on plant diversity in any of the coastal zones of the Mediterranean. However, a different picture emerged in inland areas, oases and southern slopes of mountains, where the influence of European civilization was apparent (Vavilov 1997). Vavilov’s special interest in early agrarian cultures led to an expedition to Syria, Palestine and Jordan, where there were traces of ancient agriculture. In Palestine in particular, he found useful forms of white lupins (going under the local name Tel Karam). These are distinguished by early maturity and are now widely used in breeding (Golovchenko et al. 1984). Plant collection in Sudan and Ethiopia yielded about 2000 accessions of local varieties. In Sudan, Vavilov found valuable forms of white lupin, and in Ethiopia found endemic forms of everlasting pea, chickpea, lentil and beans. The flora of Ethiopia is in many respects unique and Vavilov considered it to be an independent primary Abyssinian focus (Vavilov 1926), and later the Abyssinian Centre of diversity (Vavilov 1962).
In 1929 Vavilov organized an expedition to China (Xinjiang–Kashgar, Uch Turfan, Aksu, Kucha, Urumchi, Kulja and Hotan), Japan (Honshu, Kyushu and Hokkaido) and Korea. The purpose of his trip to northern and western China was to determine the role of Central Asia (within the limits of China) in the origin of cultivated plants of eastern Asia. Returning from northern and western China, he inspected the area close to the Chinese border around Lake Issyk-Kul and the Syr Darya river basin. Vavilov concluded from the results of this trip that Central Asia does not have the features of an independent focus of ancient agriculture: all that was cultivated there had been introduced from the east. His investigations in Japan, however, confirmed it as one of the centres of cultivated plants (the East Asiatic centre). He found that, while Japan had ‘borrowed’ some cultivated plants from China, its geographical isolation, its span in latitude, and its diversity of climate and ecology generated unique features in the cultivated flora. Wild species and cultivated forms of soybean were added to the collection following these expeditions.
Vavilov was interested for a long time in plant genetic resources of Latin America. In 1932, an invitation to the VI International Genetic Congress in the USA gave him an opportunity to inspect these regions. Vavilov visited Cuba, Mexico, Ecuador, Peru, Bolivia, Chile, Brazil, Argentina and Uruguay after the congress. Vavilov detected specific and varietal structures in cultivated plants, and received information about their history, origin and wild relatives. He collected valuable forms of kidney bean, peanuts and American species of lupin. This was Vavilov’s last overseas trip.
Vavilov also traveled widely in the territory of the former Soviet Union. He paid special attention to the mountain regions of the Caucasus and Central Asia, in which there were unique cultures and wild species, whose role in the creation of cultivated plants is not doubted. The direct connection of the Caucasus with Iran, Central Asia and Turkmenistan has resulted in some similarities with the Southwest Asiatic Centre of origin of cultivated plants. Vavilov personally participated in expeditions to more than 50 countries. In 1938–1940, he wrote essays on his journeys under the title "Five Continents”. The existing pages of this manuscript were published in 1962 and 1987 in Russian (Vavilov 1962, 1987a), and later in English by IPGRI (Vavilov 1997).

The characteristics of the principal legume accessions collected by Vavilov

Mung bean (Vigna radiata (L.) R.Wilczek)

Doctor Sofia I.Stepanova and assistant Elena I. Kazanskaya study the accessions of white lupin collected by Nikolay Vavilov

Vavilov not only collected and organized research on the assembled material, but also attempted to establish new methodologies. He was particularly keen to develop simpler and more accessible methods for determining alkaloid content in lupin. This was important in 1928-1929 as von Sengbusch, in Germany, had developed such a method but it was kept secret and the sweet strains of lupin were sold to a private firm. Under the management of N.N. Ivanov, and further elaborated by M. I. Smirnova and others, an efficient expression method was developed and adopted in VIR. In 1932, Vavilov wrote the foreword to a work by Ivanov et al. (1932) that was central to the initiation of breeding fodder (sweet) low alkaloid lupin.

Continuing Vavilov’s work

Vavilov’s work in collecting and studying genetic resources of leguminous plants has been continued by VIR scientists. The department of leguminous crops of VIR was established in 1924. Vavilov invited his friend L.I. Govorov to manage the department, and he recruited experts in leguminous plants to the staff. Govorov developed intraspecific classification for peas (Govorov 1937), organized breeding work with leguminous crops in the former USSR and created many pea cultivars. Like Vavilov, Govorov had a tragic destiny; he was arrested and disappeared. P.M. Zhukovsky was invited to manage the lupin collection. He developed and published important works on interspecific and intraspecific diversity (Zhukovsky 1929). Research on the genetic resources of lentil was done by E.I. Barulina (Vavilov’s wife). She took part in many expeditions, e.g. to Crimea, Georgia and other regions (Barulina 1930). During the Second World War the department of leguminous crops was managed by N.R. Ivanov, who made a substantial contribution to preserving the collection during the seige of Leningrad.