ISSN 1022-7954, Russian Journal of Genetics, 2011, Vol. 47, No. 6, pp. 791–802. © Pleiades Publishing, Inc., 2011. Original Russian Text © E.D. Badaeva, O.Yu. Shelukhina, O.S. Dedkova, I.G. Loskutov, V.A. Pukhalskiy, 2011, published in Genetika, 2011, Vol. 47, No. 6, pp. 783–795. 791 INTRODUCTION The hexaploid species Avena sativa (cultivated oat) and A. byzantina (red oat) are important crops culti- vated on a territory from the northern borders of agri- culture to the subtropics and highland regions [1, 2]. Oat is used in food industry (oatmeal, flakes, flour, etc.) and is of particular value for children’s and dietary nutrition. Oat has been used for a long time in medicine as a highly nutritious and therapeutic prod- uct. In addition, oat is a valuable forage product for horses and poultry, since it has a high content of indis- pensable amino acids in the protein, a rich diversity of vitamins and mineral substances, and by good ener- getic properties. Oat flour is also used in parfumery and in the production of medicinal soap. Cultivated oat A. sativa was among the main cereal crops of the traditional agriculture of the Old World being closely related to wheat and barley [3]. Plant remains of A. sativa or A. byzantina with nonshattering panicles and characteristic roundish seeds were found in archeological excavations in Europe dating the 2nd–1st centuries B. C. [4]. In Russia, the cultivation of oat was started presum- ably in the 7th century A. D. [5]. The cultivated hexaploid species of Avena show a close genetic and morphological similarity with a group of wild and weedy oats (A. sterilis, A. fatua, A. ludovici- ana, and A. occidentalis). Moreover, they are readily crossed with each other even in nature [1]. Therefore, some authors consider the wild and weedy species of hexaploid oat to be the wild forms of the cultivated spe- cies [6, 7]. The wild oat, A. sterilis, grows abundantly in different Near East and Mediterranean countries and is also found in the Caucasus, Crimea, and Turkmenistan [1, 8], often as a mix of wild wheat and barley. It is believed that A. sterilis was a progenitor of A. sativa and A. byzantina [9]. The group of weedy species includes A. occidentalis, A. ludoviciana, and A. fatua, which differ in a number of morphological traits and in the ranges. Most widely spread is A. fatua, or wild oat, which is distributed in nearly all agricultural zones of the globe. The main cen- ter of A. fatua diversity is in the mountains of Southwest Asia, especially in the Pamirs [7]. Avena occidentalis (western oat) is an endemic of Madeira, Azores, and Canary Islands, but it is also found in Portugal and Saudi Arabia. As compared to A. fatua, it is accustomed to warm climatic conditions [1, 8]. Avena ludoviciana grows in Ukraine and in the Crimea, in the Caucasus, in Central and Southwest Asia, Western Europe, and in the Mediterranean countries [8]. A close genetic rela- tionship of A. ludoviciana and A. fatua is also inferred from their morphological similarity and from the ability to readily cross with each other. At the same time, A. ludoviciana combines characteristics of other oat species (A. sativa and partly A. sterilis and A. byzantina) [10]. In connection with this, some authors regard it as Comparative Cytogenetic Analysis of Hexaploid Avena L. Species E. D. Badaeva a, b , O. Yu. Shelukhina a , O. S. Dedkova a , I. G. Loskutov c , and V. A. Pukhalskiy a a Vavilov Institute of General Genetics, Russian Academy of Sciences, Moscow, 119991 Russia e-mail: K_Badaeva@mail.ru b Engelhardt Institute of Molecular Biology, Russian Academy of Sciences, Moscow, 119991 Russia c Vavilov Institute of Plant Industry, Russian Academy of Agricultural Sciences, St. Petersburg, 190000 Russia Received November 26, 2010 Abstract—Using methods of differential C-banding of chromosomes and in situ hybridizatiion with the 45S and 5S rRNA gene probes, six hexaploid species of the genus Avena L. with the ACD genome constitution were studied to reveal evolutionary karyotypic changes. Similarity in the patterns of chromosomal C-banding and in the patterns of distribution of the rRNA gene families suggests a common origin of all hexaploid spe- cies. Avena fatua is characterized by the broadest intraspecific variation of the karyotype; this species displays chromosomal variants typical of other hexaploid species of Avena. For instance, a translocation with the involvement of chromosome 5C marking A. occidentalis was discovered in numerous A. fatua accessions, whereas in other representatives of this species this chromosome is highly similar to the chromosome of A. sterilis. Only A. fatua and A. sativa show slight changes in the morphology and in the pattern of C-banding of chromosome 2C. These results can be explained either by a hybrid origin of A. fatua or by the fact that this species is an intermediate evolutionary form of hexaploid oats. The 7C-17 translocation was identified in all studied accessions of wild and weedy species (A. sterilis, A. fatua, A. ludoviciana, and A. occidentalis) and in most A. sativa cultivars, but it was absent in A. byzantina and in two accessions of A. sativa. The origin and evolution of the Avena hexaploid species are discussed in context of the results. DOI: 10.1134/S1022795411060068 PLANT GENETICS