Search

The recessive spontaneous sy18 mutation with nonhomologous synapsis was mapped in rye. The sy18 gene was located in the centromeric region of chromosome 2R in relation to three rye SSR (simple sequence repeats) loci, i.e., Xrems1130, Xrems1203, and Xscm43, and one wheat SSR locus Xgwm132. The desynaptic sy18 gene is located in the interval between Xrems1130 and Xrems1203 markers at a distance of 0.5 cM and 3.1 cM, respectively. The possible evolutionary relationships of the mapped gene with homologous loci of the related species are discussed.

A study was made of the expression and inheritance of the sy11 mutation, which alters homologous chromosome synapsis in meiotic prophase I of rye. The abnormal phenotype proved to be determined by a recessive allele of a single sy11 gene. Univalents and multivalents were observed in homozygotes for the mutant allele. Analysis of the synaptonemal complex revealed a combination of homologous and nonhomologous synapsis in the mutant. The nonhomologous synapsis frequency significantly decreased in the course of meiotic prophase I in the mutant. The number of chiasmata per bivalent in metaphase I was 1.1 x 0.01 versus 1.8 x 0.01 in wild-type plants, and the number of univalents was 2.7 x 0.06 versus 0.5 x 0.05 in wild-type plants. As a result, a broad range of abnormalities was observed at subsequent stages of meiosis and led to the formation of defective microspores. Mutant plants were semisterile.

Studies of phenotypical expression of synaptic mutations in combination with the localization of corresponding genes on a genetic map permit individual stages of the meiotic process to be differentiated. Two rye asynaptic genes, sy1 and sy9, were mapped with the use of microsatellite markers (SSR) in the pericentromeric regions of the long chromosome arms 7R and 2R, respectively. The sy9 gene cosegregated with two SSR markers Xscm43 and Xgwm132. The asynaptic gene sy1 was mapped within the interval between the isozyme locus Aat2 and two cosegregating loci Xrems1188 and Xrems1135 that are located at a distance of 0.4 cM proximally and 0.1 cM distally with respect to the gene lous. Possible evolutionary relationships of the mapped genes with homeological loci of the Triticeae species and more distant cereal species, such as maize and rice, are discussed.

AExpression and inheritance of the sy18 mutation causing impairment of synapsis homology were studied. It was established that the abnormal phenotype is determined by a recessive allele of the sy18 gene. Univalents and multivalents are observed in homozygotes for this mutant allele. According to the electron microscopic analysis of synaptonemal complexes in mutants, homologous synapsis occurs together with nonhomologous synapsis. The sy18 gene was found to have no allelism with asynaptic genes sy1 and sy9 and with genes sy10 and sy19 causing, like sy18, disturbances in synapsis homology.

Postzygotic reproductive isolation, based on negative interactions of genes, is a key aspect of divergent speciation in plants and animals. The effect of the interaction manifests as a drastic reduction in fitness of hybrids of the first and subsequent generations, which is expressed as hybrid lethality, weakness or sterility. Both simple genetic control of genetic incompatibility, which includes interallelic negative complementation or epistatic interactions of a limited number of genes, and more complex control, based on epistatic interactions of many genes, have been described in plants. It is thought that genes for reproductive isolation are nonuniformly distributed over the genome and are related to differential adaptation. The mosaic organization of the genomes in this respect provides restoration of their structural and functional integrity upon interspecies hybridization in natural conditions. Many cultured and wild plant species, in contrast to animals, were found to be polymorphic at genes controlling interspecies incompatibility. This fact facilitates genetic analysis of incompatibility and broadens perspectives in studying the structure, functions, and molecular evolution of the genes controlling postzygotic reproductive isolation, in view of the possible leading role of these genes in adaptive speciation.

The advances in rye hybrid breeding are due to the use of self-fertile forms. Rye self-fertility is determined by mutations in one of the three gametophytic loci (S, Z, and T), which control the reaction of incompatibility. Attempts to construct synthetic populations by combining self-fertile forms selected by general combining ability failed because of high-rate selfing. A breeding scheme was proposed to include crosses of a line carrying a self-fertility mutation in the S locus with the population subject to improvement, selfing of the resulting hybrids, selection and intermating of the best inbred progenies, and subsequent elimination of the self-fertility mutation from the breeding material with the use of the Prx7 allozyme marker. The scheme can be employed in improvement of the existing rye varieties, their differentiation into populations differing in end use, and construction and improvement of complementary gene pools in hybrid breeding. To facilitate the implementation of the scheme, an original instrument was designed for high-throughput isozyme analysis.

Genetic collection of meiotic mutants of winter rye Secale cereale L. (2n = 14) was created. Mutations were detected in inbred F2 generations after self-fertilization of the F1 hybrids, obtained by individual crossing of rye plants (cultivar Vyatka) or weedy rye with plants from autofertile lines. The mutations cause partial or complete plant sterility and are maintained in collection in a heterozygous state. Genetic analysis accompanied by cytogenetic study of meiosis has revealed six mutation types. (1) Nonallelic asynaptic mutations sy1 and sy9 caused the formation of only axial chromosome elements in prophase and anaphase. The synaptonemal complexes (SCs) were absent, the formation of the chromosome "bouquet" was impaired, and all chromosomes were univalent in meiotic metaphase I in 96% (sy1) and 67% (sy2) of cells. (2) Weak asynaptic mutation sy3, which hindered complete termination of synapsis in prophase II. Subterminal asynaptic segments were always observed in the SC, and at least one pair of univalents was present in metaphase I, but the number of cells with univalents did not exceed 2%. (3) Mutations sy2, sy6, sy7, sy8, sy10, and sy19, which caused partially nonhomologous synapsis: change in pairing partners and fold-back chromosome synapsis in prophase I. In metaphase I, the number of univalents varied and multivalents were observed. (4) Mutation mei6, which causes the formation of ultrastructural protrusions on the lateral SC elements, gaps and branching of these elements. (5) Allelic mutations mei8 and mei10, which caused irregular chromatin condensation along chromosomes in prophase I, sticking and fragmentation of chromosomes in metaphase I. (6) Allelic mutations mei5 and mei10, which caused chromosome hypercondensation, defects of the division spindle formation, and random arrest of cells at different meiotic stages. However, these mutations did not affect the formation of microspore envelopes even around the cells, whose development was blocked at prophase I. Analysis of cytological pictures of meiosis in double rye mutants reveled epistatic interaction in the mutation series sy9 > sy1 > sy3 > sy19, which reflects the order of switching these genes in the course of meiosis. The expression of genes sy2 and sy19 was shown to be controlled by modifier genes. Most meiotic mutations found in rye have analogs in other plant species.

The phenotypic manifestation and genetic control of embryo lethality observed in crosses between common wheat and rye were studied. It was found that crosses between common wheat and inbred self-fertile rye lines L2 and 535 gave rise to ungerminating grains, in which the development and differentiation of the hybrid embryo are arrested. Study of the degree of embryo development in the hybrid grains obtained by crossing common wheat varieties with inbred rye lines L2 and 535 showed that genotypes of the parents affected the ratio between undifferentiated embryos of various sizes. Analysis of this trait was performed by test crosses according to a novel pedigree program with the use of interlinear hybrids and a set of fourth-generation hybrid recombinant inbred lines. Rye line L2 was shown to bear the Eml (Embryo lethality) gene, which terminates the development of the hybrid embryo in amphihaploids. The suggestion of complementary interaction between wheat and rye genes during formation of a "n ew" character in wheat-rye F1 hybrids is discussed. A method of detecting an allele not complementary to the rye Eml allele in wheat is proposed. The proposed test program allows appropriate study of the system of wheat and rye genes involved in complementary interaction in the genotype of a distant hybrid.

Data on linkage of 12 rye genes controlling morphological traits (el, Vs, ln, w, np, ct2, Hs, Ddw, cb, mn, vil, mp) with one or several isozyme markers of individual rye chromosomes (2R-7R) are presented. Linkage of the following gene pairs was established: chromosome 2R: Est3/5-el, el-beta-Glu, Sod2-el, Sod2-Vs; chromosome 3R: ln-Got4; chromosome 4R: w-Got1, np-Got1; chromosome 5R: Est4-ct2, Est6/9-ct2, ct2-Est2, ct2-Aco2, Est2-Hs, Aco2-Hs, Est2-Ddw, Aco2-Ddw; chromosome 6R: Lap2-cb, cb-Aco1, Est10-mn; chromosome 7R: Acph2/3-vi1, Got2-vi1, mp-Acph2/3. The reasons for mapping a very small number of genes in rye in spite of high intraspecific variability of this species are discussed. An approach is suggested to improve this situation by simultaneous identification and mapping of all diverse spontaneous mutations maintained in heterozygous state in various rye cultivars.

We characterized radish lines from a genetic collection on the basis of six enzyme systems, identified genes controlling these enzymes, and examined joint inheritance of some biochemical and morphological traits.

The genetic map of rye consisting of 149 RFLP, 20 isozyme and 12 microsatellite markers was developed. Using the collection of cross-hybridizing probes, the presence of multiple translocations in rye genome with respect to wheat and barley genomes was shown. However, within large regions of genome a strict collinearity of marker order was observed that allow us to use the method of comparative mapping for an introduction of new genes. In the developed genetic map 18 morphological and breeding-valuable genes mapped in different rye populations were integrated. The comparative analysis of homeological loci in genomes of Triticeae species as well as in genomes of rice and maize was carried out. The genes controlling a number of morphological traits, plant height, photoperiodic response and winter/spring growth habit were shown to be conserve among cereals and to form clear homoeologous rows.

The number of seeds and seed setting in the main spike were studied in primary octoploid triticale obtained from crosses between the common wheat cultivar Chinese Spring and 66 inbred rye lines. In some rye lines, the mutations of self-fertility were identified in the S, Z, or T incompatibility loci. The number of seeds was determined under controlled self-pollination of the main spike. In the set of triticale examined, each trait exhibited high variation. Hence, the rye lines were suggested to carry gene alleles both increasing and decreasing these traits in triticale. All the traits studied were significantly influenced by environmental conditions. Ten triticale lines were identified, which had the largest seed setting under self-pollination. Seven out of ten samples with the high number of seeds carried mutations in the T locus and in the three samples, the unidentified self-fertility mutations were present. The triticale lines with mutations in the S and Z loci displayed much lower self-fertility on average. The ways and means of identifying and mapping the rye gene responsible for distinctions between the triticale quantitative traits are discussed.

When breeding the primary spring octoploid triticale derived from crosses of various inbred rye lines to wheat Chinese Spring, the effects of the rye genotype and growth conditions on the plant height and proportion of the first, second, and final (pedicle) internodes to the entire stem length were studied. Two triticale groups were examined: homozygotes for the dominant (Ddw1) and recessive (ddw1) alleles of the gene responsible for short stem in rye. In the short stem triticale lines carrying the Ddw1 alleles, the plants were 20 cm shorter on average than those in the ddw1-carrying lines, and the distribution of the two triticale groups overlapped significantly. In both groups, the lines significantly differing in plant height could be differentiated, because of allelic diversity of the additional genes controlling this trait along with the Ddw gene. In most triticale lines, especially in the Ddw1-carrying ones, the plant height was much reduced under unfavorable growth conditions. At the same time, a short-stem line was isolated, which is characterized by ecological plasticity, like the maternal wheat cultivar. In the triticale studied, the stem structure depended on the short-stem rye genotype. The two-year study showed that in the triticale carrying the dominant allele of this gene, the first internode is significantly extended, whereas the upper (pedicle) internode is reduced, which increases plant lodging resistance. The differences revealed between the rye lines as well as their effect on the quantitative triticale traits are discussed in view of a variant of the hybridological analysis, which had been previously proposed for identification and mapping of the correspondent rye genes.

In F2 hybrids between self-sterile plants of the Volkhova cultivar and self-fertile lines with established self-fertility mutations (sf-mutations) at the major incompatibility loci S (1R), Z (2R), and T (5R), the effect of sf-mutations on the inheritance of secalin-encoding, isozyme, and morphological markers located on the same chromosomes was investigated. Linkage between loci Prx7 and S and locus Sec3 coding for high-molecular-weight secalins on chromosome 1R was shown for the first time The frequency of recombination between Prx7 and Sec3 and between S and Sec3 was 29.1 +/- 4.8% and 30.9 +/- 7.0%, respectively. Independent inheritance of locus Z and isozyme markers of chromosome 2R, Est3/5 and beta-Glu, from locus Sec2 encoding 75-kDa gamma-secalins was shown; in hybrids, the recombination frequency between Est3/5 and locus Z varied from 19.2 +/- 8.1 to 50%. Independent inheritance of morphological (Ddw and Hs) and isozyme markers (Est4, Est6/9, and Aco2) of chromosome 5R from locus T located on the same chromosome was demonstrated.