Features of crossability, haploidy and polyembryony in hybrid combinations between common barley Hordeum vulgare L. (2n = 14) and wheat-rye substitution lines Triticum aestivum L., cultivar Saratovskaya 29/Secale cereale L., cultivar Onokhoiskaya

The role of individual chromosomes of rye in the manifestation of crossability and seedling development in hybrid combinations between common barley Hordeum vulgare L., cultivar Nepolegayushchii (2n = 14) and five wheat-rye substitution lines Triticum aestivum L., cultivar Saratovskaya 29/Secale cereale L., cultivar Onokhoiskaya (2n = 40 wheat + 2 rye chromosomes). Crossability, which was measured by two parameters--frequency of set grains and frequency of grains with embryos--was shown to be significantly affected by each of the five rye chromosomes examined: 1R, 2R, 3R, 5R, and 6R; the development of barley haploids was affected by rye chromosomes 1 R, 3R, and 5R. We were the first to demonstrate that polyembryony could be induced by mutual effects of barley cytoplasm and rye chromosome 1R. Possible mechanisms controlling the development of haploids and twins in hybrid combinations H. vulgare x T. aestivum/S. cereale are discussed. The conclusion is drawn that hybrid combinations between common barley and wheat-rye substitution lines can serve as new models for studying incompatibility mechanisms in distant crosses and genetic control of parthenogenesis.     

Hybrid dwarfness in crosses between wheat (Triticum aestivum L.) and rye (Secale cereale L.): a new look at an old phenomenon

The existence of hybrid dwarfs from intraspecific crosses in wheat (Triticum aestivum) was described 100 years ago, and the genetics underlying hybrid dwarfness are well understood. In this study, we report a dwarf phenotype in interspecific hybrids between wheat and rye (Secale cereale). We identified two rye lines that produce hybrid dwarfs with wheat and have none of the hitherto known hybrid dwarfing genes. Genetic analyses revealed that both rye lines carry a single allelic gene responsible for the dwarf phenotype. This gene was designated Hdw‐R1 (Hybrid dwarf‐R1). Application of gibberellic acid (GA₃) to both intraspecific (wheat–wheat) and interspecific (wheat–rye) hybrids showed that hybrid dwarfness cannot be overcome by treatment with this phytohormone. Histological analysis of shoot apices showed that wheat–rye hybrids with the dwarf phenotype at 21 and 45 days after germination failed to develop further. Shoot apices of dwarf plants did not elongate, did not form new primordia and had a dome‐shaped appearance in the seed. The possible relationship between hybrid dwarfness and the genes responsible for the transition from vegetative to generative growth stage is discussed.     

Comparative molecular-genetic mapping of genomes of rye (Secale cereale L.) and other cereals

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.     

Molecular markers in management of ex situ PGR – A case study

Worldwide germplasm collections contain about 7.4 million accessions of plant genetic resources for food and agriculture. One of the 10 largest ex situ genebanks of our globe is located at the Leibniz Institute of Plant Genetics and Crop Plant Research in Gatersleben, Germany. Molecular tools have been used for various gene bank management practices including characterization and utilization of the germplasm. The results on genetic integrity of long-term-stored gene bank accessions of wheat (self-pollinating) and rye (open-pollinating) cereal crops revealed a high degree of identity for wheat. In contrast, the out-pollinating accessions of rye exhibited shifts in allele frequencies. The genetic diversity of wheat and barley germplasm collected at intervals of 40 to 50?years in comparable geographical regions showed qualitative rather than a quantitative change in diversity. The inter- and intraspecific variation of seed longevity was analysed and differences were detected. Genetic studies in barley, wheat and oilseed rape revealed numerous QTL, indicating the complex and quantitative nature of seed longevity. Some of the loci identified were in genomic regions that co-localize with genes determining agronomic traits such as spike architecture or biotic and abiotic stress response. Finally, a genome-wide association mapping analysis of a core collection of wheat for flowering time was performed using diversity array technology (DArT) markers. Maker trait associations were detected in genomic regions where major genes or QTL have been described earlier. In addition, new loci were also detected, providing opportunities to monitor genetic variation for crop improvement.     

Genetic control of embryo lethality in crosses between common wheat and rye

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.     

Features of Crossability, Haploidy and Polyembryony in Hybrid Combinations between Cultivated Barley Hordeum vulgare L. (2n = 14) and Wheat-Rye Substitution Lines Triticum aestivum L., Cultivar Saratovskaya 29/Secale cereale L., Cultivar Onokhoiskaya

The role of individual chromosomes of rye in the manifestation of crossability and seedling development in hybrid combinations between cultivated barley Hordeum vulgare L., cultivar Nepolegayushchii (2n = 14) and five wheat-rye substitution lines Triticum aestivum L., cultivar Saratovskaya 29/Secale cereale L., cultivar Onokhoiskaya (2n = 40 wheat + 2 rye chromosomes). Crossability, which was measured by two parameters—frequency of set grains and frequency of grains with embryos—was shown to be significantly affected by each of the five rye chromosomes examined: 1R, 2R, 3R, 5R, and 6R; the development of barley haploids was affected by rye chromosomes 1R, 3R, and 5R. We were the first to demonstrate that polyembryony could be induced by mutual effects of barley cytoplasm and rye chromosome 1R. Possible mechanisms controlling the development of haploids and twins in hybrid combinations H. vulgare × T. aestivum/S. cereale are discussed. The conclusion is drawn that hybrid combinations between cultivated barley and wheat-rye substitution lines can serve as new models for studying incompatibility mechanisms in distant crosses and genetic control of parthenogenesis.__________Translated from Genetika, Vol. 41, No. 6, 2005, pp. 784–792.Original Russian Text Copyright © 2005 by Pershina, Belova, Devyatkina, Rakovtseva, Kravtsova, Shchapova.     

Features of recombination of nuclear genome in back crossed offspring of barley-wheat hybrids Hordeum vulgare L. (2n=14) x Triticum aestivum L. (2n+42) with the use of SSR-analysis

The backcross progenies of the barley-wheat hybrids Hordeum vulgare L. (2n = 14) x Triticum aestivum L. (2n = 42) and two alloplasmic lines derived from them were studied using microsatellite markers of barley and wheat. The F1 hybrids and first backcross plants BC1 contained the genetic material of both cultivated barley and the cultivars of common wheat involved in developing of these hybrid genotypes. The genomes of BC3, BC4, and alloplasmic lines contained no microsatellite markers of the cultivated barley, whereas chromosomes of each homeologous group of common wheat were identified. In chromosomes of backcross progenies BC3, BC4, and alloplasmic lines yielded by backcrosses of hybrids and various common wheat cultivars, microsatellite markers of the parental wheat cultivars were shown to undergo recombination.     

Polymorphism of heterochromatin C-blocks of rye genome chromosomes in rye-wheat amphidiploids and their chromosome substitution lines

Polymorphism of heterochromatin C-blocks in chromosomes of rye genome has been studied in the F1BC1 hybrids and the D/A substitution lines of rye-wheat amphidiploids (Verasen x L374, Novosibirskaya x x L246)--secalotriticum for revealing cytogenetic markers of rye chromosomes. An increase in polymorphism for the presence and value of heterochromatin blocks in chromosomes of rye genome was shown in the F1BC1 hybrids ((Verasen x L374) x L145 x L145) and unstable genotypes of the F6BC1 chromosome substitution lines (line 118 (Novosibirskaya x L246) x Reso x Reso), line 104 ((Verasen x x L374) x Garmoniya x Garmoniya) that was related to activation of mobile genetic elements present in cereals. Heterochromatin markers of all seven chromosomes in rye genome were revealed. The polymorphism system of heterochromatin blocks may serve as a marker for specificity of the linear chromosome structure during reconstruction of synthetic cereal genomes, and as a test for cytological and morphogenetic stability of hybrid polygenomes in a series of generations.     

The transfer of a powdery mildew resistance gene from Hordeum bulbosum L to barley (H. vulgare L.) chromosome 2 (2I)

Hordeum bulbosum L. is a source of disease resistance genes that would be worthwhile transferring to barley (H. vulgare L.). To achieve this objective, selfed seed from a tetraploid H. vulgare x H. bulbosum hybrid was irradiated. Subsequently, a powdery mildew-resistant selection of barley phenotype (81882/83) was identified among field-grown progeny. Using molecular analyses, we have established that the H. bulbosum DNA containing the powdery mildew resistance gene had been introgressed into 81882/83 and is located on chromosome 2 (2I). Resistant plants have been backcrossed to barley to remove the adverse effects of a linked factor conditioning triploid seed formation, but there remains an association between powdery mildew resistance and non-pathogenic necrotic leaf blotching. The dominant resistance gene is allelic to a gene transferred from H. bulbosum by co-workers in Germany, but non-allelic to all other known powdery mildew resistance genes in barley. We propose Mlhb as a gene symbol for this resistance.     

Cytogenetics of the trigeneric hybrid, (Hordeum vulgare ×Triticum aestivum) ×Secale cereale

Summary Chromosome pairing was studied in hybrids of (Hordeum vulgare ×Triticum aestivum) ×Secale cereale. Chiasma frequency per cell varied from 1.94 to 3.16 between the different hybrids. This variation was attributed to genetic variability in rye parents which affected homoeologous pairing. The pairing of rye chromosomes as revealed by Giemsa C-banding was a combination of nonhomologous association between rye chromosomes and associations with chromosomes of wheat and barley. Contribution No. 634 Ottawa Research Station     

Fitness estimation through performance comparison of F1 hybrids with their parental species Oryza rufipogon and O. sativa

BACKGROUND AND AIMS: Introgression of crop genes into populations of wild relatives has important implications for germplasm conservation as well as for the persistence of novel transgenes in wild populations. Studies of hybrid fitness can be used to evaluate the potential for introgression to occur following episodes of interspecific hybridization. METHODS: This study estimated relative fitness of interspecific hybrids through performance comparison of F(1) hybrids with their parental species, a cultivated rice (Oryza sativa) Minghui-63 and perennial common wild rice (O. rufipogon) under the cultivation conditions. KEY RESULTS: Compared with their parents, the hybrids had the lowest values of seedling survival ability, pollen viability and seed production; intermediate values of seed germination, spikelet production and flag leaf areas; and the highest values of plant height, number of tillers and panicles. The hybrids performed poorly at the stage of sexual reproduction, although they had a slightly higher hybrid vigour at the vegetative growth stage and better tillering ability than their wild parent. There were no significant differences in composite fitness across the whole life-history between the hybrids and their wild parental species. CONCLUSIONS: Rice genes, including transgenes, might persist in wild rice populations through vegetative and sexual reproduction. Further studies are needed to examine whether the extent of gene flow from rice is sufficiently significant to influence genetic diversity in wild populations of O. rufipogon, a species that has become endangered in some regions of south-east Asia.     

Genetic Control of Embryo Lethality in Crosses between Common Wheat and Rye

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 “new” 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.__________Translated from Genetika, Vol. 41, No. 8, 2005, pp. 1075–1083.Original Russian Text Copyright © 2005 by Tikhenko, Tsvetkova, Voylokov.     

Effects of Parental Embryo and Endosperm Mitotic Cycle Times on Development of Hybrids Between Barley and Rye

Seven different barley/rye crosses were made using genotypeshaving close (predicted compatible) or dissimilar (predictedincompatible) mean cell doubling times. The relative successof the crosses was determined by a cytological study of earlyhybrid seed development and by the yield of 16-day-old hybridembryos. The results support the hypothesis that parental developmentalrates must be similar for successful hybridization. The degenerationof the hybrid endosperm occurred earlier in the predicted incompatiblecrosses than in the more compatible ones. Fewer hybrid embryoswere harvested at day 16 from predicted incompatible crossesthan from compatible crosses. We conclude that development ofhybrid embryos depends on the early stages of endosperm developmentand that mitotic rates in parental endosperms are more importantthan in embryos. Hordeum vulgare L., Secale cereale L., barley, rye, hybrid, mean cell doubling time, embryo, endosperm     

Molecular marker analysis of hypoploid regenerants from cultures of barley x Canada wild rye.

Canada wild rye (CWR, Elymus canadensis L., 2n = 4x = 28) is a potential source of genes for disease resistance and environmental tolerance in barley (Hordeum vulgare L., 2n = 2x = 14). Tissue cultures were initiated from immature inflorescences of CWR x 'Betzes' barley hybrids to promote CWR introgression into barley through possible tissue culture induced chromosome breakage and exchange. Among the plants regenerated, some were missing one (2n = 20) or part of one (2n = 20 + telo) chromosome. The objective of this study was to identify the missing chromosome or chromosome arm in these regenerants through the analysis of molecular (RFLP) markers that previously had been mapped in barley. Forty-six hypoploid regenerants that traced to 30 separate explants obtained from 10 interspecific hybrid plants were evaluated. DNA was digested with the restriction enzyme HindIII, Southern blotted, and probed with 39 genomic and cDNA barley clones that identified sequences polymorphic between barley and CWR. Eight of these probes identified band loss patterns that separated the regenerants into two groups. One group, all with barley cytoplasm, were missing a CWR chromosome homoeologous to barley chromosome 3; a second group, all with CWR cytoplasm, were missing a CWR chromosome homoelogous to barley chromosome 7. These results indicated that chromosome elimination in culture was not random. The two cytoplasm groups were further differentiated by probes that identified band shifts. These band shifts were caused by differences in DNA methylation. Key words : Hordeum vulgare, aneuploidy, Elymus canadensis, tissue culture.     

Genetic variation and self-incompatibility within and outside a Rorippa hybrid zone (Brassicaceae)

Rorippa amphibia and R. sylvestris are both self-incompatible, perennial species. In northern Germany they show a geographic pattern of interspecific gene flow: R. amphibia and R. sylvestris form a hybrid zone at the river Elbe but do not hybridise elsewhere in northern Germany. In the present paper we analyse the relationship between molecular diversity, seed set and seed germination within and outside the hybrid zone. In both species we observed high genetic variation and high seed set in the hybrid zone, and low genetic variation and low seed set outside the hybrid zone. In R. amphibia, high genetic variation is correlated with high seed set, but with low germination rates of the seeds. The results of an isolation experiment show that self-incompatibility is maintained in the parental species and their hybrids. The impact of genetic self-incompatibility on hybrid zone formation and hybrid fitness is discussed.     

Variable modes of inheritance of morphometrical traits in hybrids between Drosophila melanogaster and Drosophila simulans.

We investigated body-size inheritance in interspecific sterile hybrids by crossing a Drosophila simulans strain with 13 strains of Drosophila melanogaster, which were of various origins and chosen for their broad range of genetic variation. A highly significant parent-offspring correlation was observed, showing that the D. melanogaster genes for size are still expressed in a hybrid background. Superimposed on to this additive inheritance, the size of hybrids was always less than the mid-parent value. This phenomenon, which at first sight might be described as dominance or overdominance, is more precisely interpreted as a consequence of a hybrid breakdown, that is, a dysfunction of the parental genes for size when put to work together. This interpretation is enforced by the fact that phenotypic variability was much more prevalent in hybrids than in parents. We also analysed body pigmentation inheritance in the same crosses and got a very different picture. There was no increase in the phenotypic variance of F(1) hybrids and only a low parent-offspring correlation. Apparent overdominance could be observed but in opposite directions, with no evidence of hybrid breakdown. Our data point to the possibility of analysing a diversity of quantitative traits in interspecific hybrids, and indicate that breakdown might be restricted to some traits only.     

Development of new cytoplasmic-genetic male-sterile lines in pigeonpea from crosses betweenCajanus cajan (L. Millsp. andC. scarabaeoides (L.) Thouars

Exploitation of hybrid vigour is quite possible in cross-pollinated crops. However, pigeonpea is a grain legume crop with a moderate level of cross-pollination (20-70%), which is mainly aided by insect pollinators. As a first step, hybrids based on genetic male sterility (GMS) were developed in pigeonpea, but the hybrid seed production technique is not farmer-friendly, because in the hybrid seed production plot 50% of the population, which are male-fertile in the female rows, have to be eliminated in time before contamination. This requires skilled labour and is a time-consuming process, which increases the cost of hybrid seed production. Therefore, the objective of this study was to develop cytoplasmic-genetic male-sterile (CGMS) lines in pigeonpea through wide hybridization, which would be very suitable for hybrid seed production. Two CGMS lines, viz. CORG 990052 A and CORG 990047, were developed by interspecific hybridization of Cajanus cajan and C. scarabaeoides. Restorers were identified and three CGMS-based pigeonpea hybrids were developed. The hybrid COPH 3 is found to be promising in Tamil Nadu State, India.     

Heterosis for chiasma frequency and quantitative traits in common beans (Phaseolus vulgaris L.)

Summary Ten genotypes, including inbreds, hybrids, and advanced populations, were examined in order to elucidate the relationship between position and frequency distribution of chiasmata and quantitative traits, including yield heterosis in common beans. The hybrid and advanced population groups were determined to possess 83% and 54% increased chiasma frequency, respectively in contrast to inbred lines. The increase in chiasma frequency of these populations was further manifested in a high number of interstitial chiasmata. The regular and superior chromosome behaviour of the hybrids was found to be positively associated with quantitative measures on bean yield, harvest index and bean yield efficiency. The results were discussed from the point of view that: a) increased interstitial chiasmata may provide an effective mechanism for maintaining genetic diversity and heterosis in hybrid populations; and b) heterosis for chiasma frequency and quantitative traits may be due to dispersed genes on the chromosomes having combined intra-and interallelic interactions. The data provide evidence for the existence of positive associations between interstitially localized chiasmata with its recombination potential and regular chromosome behaviour to bean yield heterosis. The role of enhanced interstitial chiasmata to promote higher levels of genetic variation and heterozygous advantage is discussed.     

Genomic diversity in aneudiploid (2n = 38) and diploid (2n = 40) Glycine tomentella revealed by cytogenetic and biochemical methods.

Of the 15 perennial species of the subgenus Glycine Willd., G. tomentella Hayata is unique in that it has four cytotypes (2n = 38, 40, 78, and 80) and a wide range of geographical distributions. The objective of this study was to uncover the genomic diversity among accessions of aneudiploid (2n = 38) and diploid (2n = 40) G. tomentella based on crossability rate, hybrid seed and seedling viability, meiotic chromosome pairing of F1 hybrids, and seed protein and protease inhibitor profiles. Aneudiploid and diploid G. tomentella accessions were divided into two (D1 and D2) and three [D3(A,B,C), D4, and D5] groups, respectively, based on previous isozyme studies. Crossability rate, intergenomic hybrid viability, degree of chromosome pairing, total seed protein profiles, and trypsin and chymotrypsin inhibitor banding patterns confirmed the isozyme grouping with minor disagreements. A consistent variation was not observed among the aneudiploid accessions in any method of analysis used in this study. Similarly, cytogenetic analysis and the total seed protein profiles did not show dissimilarity among the accessions from Papua New Guinea (PNG; the D3 group) and north of Mitchell River in Northern Queensland [N.Qld(n)]. However, trypsin and chymotrypsin inhibitor analysis revealed that the PNG accessions were distinctly different from N.Qld(n) accessions. The D4 and D5 group accessions were clearly distinguishable by both cytogenetic and biochemical methods. Thus, this study indicates the presence of four genomic groups among G. tomentella (2n = 38, 40) accessions, including the aneudiploids D1 and D2 in one group and diploids in three groups (D3, D4, and D5). These findings will be useful in further genome analysis and add to our present understanding of the biosystematics of the genus Glycine.