MOLECULAR ANALYSIS OF THE GENETIC DIVERSITY OF POPULATIONS OF SWEET CLOVER (Melilotus dentatus Pers.)

Abstract

S u m m a r yIn the studies of Melilotus dentatus Pers. populations from different geographically remote areas (North Caucasus and Kazakhstan), a compex approach of intra-and inter-population analysis of taxonomically important molecular markers (ITS) was used. The analysis of receptor gene nfr5 was also made. It is shown that the Melilotus dentatus Pers. plants differ at both intra-and inter-population levels. A consolidation of sweet clover's populations to clusters is observed according to their geographic location. An independent distribution of populations on receptor part of nfr5 gene concerning cluster structure of ITS region is determined.Keywords: Melilotus dentatus Pers., genetic diversity, nfr5 gene.In global agriculture, sweet clover is a fodder plant less important than other leguminous forage grasses. At the same time, detailed recent studies show a number of valuable economical properties of Melilotus dentatus Pers.: high drought resistance, winter hardiness, along with better immunity against pests and diseases compared with other legumes (1), and better consumption by animals due to lower content of coumarin (2). Its ability to grow on saline lands allows using sweet clover in soil recultivation through the creation of saline-resistant legume-rhizobial complex. Such programs require the plants with improved symbiotic efficiency, which is largely determined by the genotype.The peculiarity of legume-rhizobium symbiosis is a signal exchange between both partners whose signaling molecules trigger the mechanism of formation of a specialized new organ -nodule. In response to the specific inducers -flavonoids released in soil by a host plant, nitrogen-fixing bacteria start the production of signaling molecules (Nod-factors) that initiate the formation of root nodules in leguminous plants (3). All Nod-factors are lypochytho-oligosaccharides. Legume plants have seven genes presumably involved in signaling recognition and interaction with symbiotic rhizobia (4). The family of LYK genes is of particular interest, which include nfr1 and nfr5 first identified in Lotus japonicus (3, 5), Sym10 and Sym2 in Pisum sativum (3), as well as NFP gene in diploid alfalfa (6, 7). These genes encode LysM-containing receptor kinase, and they have domain structure typical for plants: extracellular LysM-domains -probable participants in the reception of Nod-factor, a transmembrane domain, and an intracellular domain of serine / threonine kinase.The genes containing LysM-encoding regions (LysM-motifs) belong to an ancient and quite diverse group widespread in all kingdoms except Archaea (7). Phylogenetic analysis has shown that some sequences of bacterial LysM-motifs have common roots with nucleotide sequences of fungi, plants, insects and animals. This allowed suggesting that one group of these genes had been formed before the divergence of plants and animals, while the other group is the result of convergent evolution. A structural resemblance of LysM-containing protein kinase and the peptidogycan component of bacterial ce...