The effectiveness of molecular markers for the identification of leaf rust resistance genes Lr28, Lr35 and Lr47 transferred to common wheat from Ae. speltoides was assessed using samples of Triticum spp. and Aegilops spp. The markers Sr39F2/R3, BCD260F1/35R2 of the gene Lr35 and PS10 of the Lr47 gene were characterized by high efficiency and were revealed in the lines of common wheat containing these genes, and samples of Ae. speltoides species, the donor of these genes. The marker SCS421 of the Lr28 gene and the markers Sr39#22r, Sr39#50s, BE500705 of the Lr35/Sr39 genes turned out to be less specific. The marker SCS421 was amplified in the samples of the T. timopheevii species, line KS90WRC010 (Lr41), the cultivar of common wheat Pamyati Maystrenko, obtained using synthetic hexaploid T. timopheevii × Ae. tauschii and introgressive lines obtained using Ae. speltoides. The marker BE500705, which indicates the absence of the Lr35/Sr39 genes, was not revealed in the lines TcLr35 and MqSr39, in Ae. speltoides, Ae. tauschii and T. boeoticum (kk-61034, 61038). Analysis of the nucleotide sequences of amplification products obtained with the markers SCS421 and Sr39#22r indicated their low homology with TcLr28 and TcLr35. Using molecular markers, a different distribution of the Lr28 (77%), Lr35 (100%) and Lr47 (15%) genes in 13 studied samples of Ae. speltoides was shown. In introgressive lines derived from Ae. speltoides, contemporary Russian cultivars of common wheat and triticale the Lr28, Lr35, Lr47 genes were not revealed.

: Different hypotheses concerning durable plant resistance against different pest were tested: 1) resistance is weak and polygenetically controlled; 2) resistance depends on "residual effect" of oligogenes that were overcome by pests. Contrast pair of plants and pests were used in experiments: wheat, barley--facultative parasite Bipolaris sorokiniana Shoem., wheat--obligate parasite Puccinia recondita Rob. ex Desm., sorghum--greenbug Schizaphis graminum Rond. Differential interaction between parasite and host plant resulted in their increased compatibility under long reproduction of parasite on resistant varieties were regarded as criteria of quick overcoming of resistance. The results did not support any hypothesis. The rate of adaptation of B. sorokiniana to the resistant varieties of wheat and barley did not depend on the level of resistance expression (weak, moderate or strong) and genetic control (oligogenic, polygenic or cytoplasmatic). It was shown by hybridological analysis that "residual effect" of oligogenes of sorghum resistance against greenbug depended on small resistance genes, that can be independent or weakly connected with marker oligogene. These data allows to doubt in phenomenon of "residual effect" of oligogenes. It was shown that non specific pathogenicity of parasitic fungi increased during their reproductions on sensitive varieties of plants. Thus, cultivation of sensitive varieties causes damage of crop culture non only because of their own losses, but also by increasing the infection of moderately resistant varieties.

Combined inheritance of oligogenes (Sgr1, Sgr4, Sgr5, and Sgr6) and a weakly expressed resistance to infestation with virulent greenbug clones was studied in sorghum. Under these conditions, the resistance was shown to depend on the interaction between minor resistance genes of the host plant and the virulence genes of the pest rather than on the "residual effect" of oligogenes. The minor genes can be independent of or weakly linked to the major resistance gene. They differentially interact with phytophage genotypes and, contrary to Van der Plank's postulates, are not responsible for the long-term (horizontal) resistance. The possibility of rapidly overcoming the effect of minor genes was confirmed by observation of seasonal dynamics of a natural aphid population on a resistant variety.