[Cytogenetic analysis of hybrids resistant to yellow rust and powdery mildew obtained by crossing common wheat (Triticum aestivum L., AABBDD) with wheat of the Timopheevi group (AtAtGG)]. / Tsitogeneticheskii analiz ustoichivykh k buroi rzhavchine i muchnistoi rose gibridov, poluchennykh ot skreshshivaniia miagkoi pshenitsy (Triticum aestivum L., AABBDD) s pshenitsami gruppy Timopheevi (AtAtGG).

The karyotypes of 47 hybrid lines obtained from crosses of common wheat Triticum aestivum L. (cv. Rodina and line 353) with Triticum timopheevii Zhuk, (AtAtGG) and related species T. militinae Zhuk. et Migusch. (AtAtGG) and T. kiharae Dorof. et Migusch. (AtAtGGDsqDsq) were analyzed by C-banding. Most lines were resistant to yellow rust and powdery mildew. The introgression of alien genetic material to the common wheat genome was realized via substitutions of complete At-, G-, and D-genome chromosomes, chromosome arms, or their fragments. The pattern of chromosome substitutions in resistant lines differed from that in introgressive hybrids selected for other traits. Substitutions of chromosomes 6G, 2At, 2G, and 5G were revealed in 31, 23, 18, and 13 lines, respectively. Substitutions of chromosomes 4G-, 4At, and 6At were not observed. In 15 lines, a 5BS. 5BL-5GL translocation was identified. High frequency of substitutions of chromosomes 2At, 2G, 5G, and 6G indicate that they may carry the resistance genes and that they are closely related to the respective homoeologous chromosomes of common wheat that determines their high compensation ability.

The nature of unstable insertion mutations and reversions in the locus cut of Drosophila melanogaster: molecular mechanism of transposition memory.

The segment of the locus cut containing the mobile genetic element mdg4 (gypsy) insertions which induce unstable ct and ct mutations has been cloned. Both mutations depend on the insertion of mdg4 into the same sequence, which coincides with that in ct allele. The ct mutation differs from ct by additional insertion of a novel mobile element jockey into mdg4. Jockey is 2.8 kb long, represented by 2-100 copies per genome, very homogeneous and lacks long terminal repeats (LTRs). The excision of mdg4 takes place in stable ct reversions. On the other hand, a complete single LTR is retained in the case of unstable ct reversions characterized by a high level of reverse directed transpositions of mdg4 into the locus cut. The LTR serves as a guide for reinsertion of mdg4 itself or mdg4 with jockey into the same site of the genome. A possible mechanism of transposition memory (homologous recombination with extrachromosomal circular DNA) is discussed.