Composition of the collection of wild apple-tree species and its prospects for use in breeding

Background. Wild apple-tree species (Malus Mill., Rosaceae) are an important reserve of sources of economically valuable traits for the needs of present and future breeding. Particular attention was paid to the immunological characteristics of the gene pool. The main genes of disease resistance contained in wild species contribute to the dominance of this feature and its fixation in the progeny. However, constantly evolving virulence of pathogens poses the need to search for sources of new non-identical genes of disease resistance and use them in breeding practice. In addition, the task of developing late flowering cultivars is quite urgent because in recent years late spring frosts have become more and more frequent and caused significant damage to the yield of apple-trees and other fruit crops. Therefore, the need to mobilize, preserve and study the genetic diversity of wild apple-tree species is a necessary condition for the selection of valuable forms and their use in breeding practice.Materials and methods. The collection of wild apple-tree species maintained at Maikop Experiment Station of VIR was established thanks to the efforts of numerous collecting teams launched by the Station and VIR to the various centers of crop origin. At present, the collection comprises 319 species, varieties and forms representing the sections Docyniopsis (C.K. Schneid.) Langenf., Sorbomalus Zabel., Gymnomeles Koehne., Chloromeles (Decne) Rehd. and Malus on the systematics of V. Langenfelds. Economic and biological features of the species' accessions have been studied according to the guidelines of VIR.Results and conclusions. The long-term study of the collection resulted in identifying species, forms and interspecific hybrids with such valuable features as high yield, resistance to diseases, late flowering period as well as early fruiting, short stem, ornamentality and others. The most promising are the species with a set of valuable features. For example, within the Sorbomalus section, high annual yield, disease resistance and ornamental qualities were observed in M. sieboldii (Rehd.) Langenf. (k-43201), M. x sargentii Rehd. (k-2428), M. x floribunda Siebold (k-2346) as well as in the hybrids M. sieboldii х Spartan (k- 41289) and M. xfloribunda х Renet Simirenko (k-41285); within the Gymnomeles section, in M. baccata (L.) Borkh. (k-2316, k-2317, k- 2327, etc.), M. hupehensis (Pamp.) Rehd. (k-14945), M. mandshurica (Maxim.) Kom. subsp. sachalinesis (Kom.) Likh. (k-890A); within the Malus section, in M. xprunifolia (Willd.) Borkh. (k-2444, k-2430). In addition, late flowering and disease resistance characterize some forms of M. orientalis (Ugl.) Juz. (k-14953, k- 17979, k-29483, etc.) and M. pumila Mill. (k-2383 and k-2385). Some forms of M. x purpurea (Barb.) Rechd. (k- 2393, k-2396) and M. spectabilis (Ait.) Borkh. (k- 2416, k-24995) are distinguished by their exceptional ornamental effec