The effect of reciprocal translocations on segregation and multivalent formation in autotetraploids of rye,Secale cereale

Chromosomal segregation, and the frequency of large multivalents in Secale cereale were studied in autotetraploid duplex translocation heterozygotes. Models for estimating expected segregations and frequencies of multivalents were developed incorporating the probabilities of different chromosomal segments being bound by chiasmata. It appeared that the segregation of the two translocations tested fitted quite well the expected corrected segregation ratio of approximately 1: 11.5: 1, suggesting that induced preferential pairing was not strong enough to enhance preferential segregation resulting from random translocation segregation. Interspecific hybrids with S. montanum carrying the same translocations showed strong preferential pairing, i.e. significant deviation from the expected ratios.Three translocations tested (two not tested for segregation) showed a decrease in multivalent frequency mainly attributable to preferential pairing, especially in cases where the breakpoint was near one chromosome end. Possible reasons why preferential pairing is expressed here and not in the segregations are discussed.     

Absence of qualitative genes controlling interspecific pairing in rye B chromosomes

Summary The meiotic behaviour of hybrids between Secale cereale carrying B chromosomes and S. vavilovii has been studied in order to estimate the effects of B chromosomes on hybrid meiotic pairing. The possible effect of Bs on the meiotic pairing of the offspring from backcrosses with S. vavilovii has been studied also. The results obtained clearly indicate that no detectable differences existed in chromosome pairing of hybrids with or without B chromosomes. The hypothetical existence of epistatic genes on cereale genome masking the effect of Bs has been rejected after the results obtained in backcrosses. Therefore, lack of qualitative genes controlling interspecific pairing on rye B chromosomes has been concluded. A quantitative effect of B chromosomes was detected only when they were in alien cytoplasm.     

Intergeneric hybridization and C-banding patterns inHordelymus (Triticeae,Poaceae)

Crosses ofHordelymus europaeus (2n = 4x = 28) with four genera in theTriticeae were attempted. Adult hybrids were obtained in combinations withHordeum bogdanii (2x),Hordeum depressum (4x), andSecale cereale (2x). The meiotic pairing was very low in the hybrids withH. bogdanii andSecale cereale (0.12 and 0.30 chiasmata/cell, respectively), whereas high pairing (9.90 chiasmata/cell) was found in hybrids withH. depressum due to autosyndetic pairing ofH. depressum chromosomes. The chromosome complement ofHordelymus europaeus comprised 16 metacentrics, 8 submetacentrics, and 4 SAT-chromosomes. The Giemsa C-banding patterns of the chromosomes were characterized by small to minute bands at no preferential positions. It is hypothesized thatHordelymus europaeus may genomically be closest related toTaeniatherum andPsathyrostachys spp.     

Interaction between rye B-chromosomes and wheat genetic systems controlling homoeologous pairing

The interactive effect on homoeologous pairing of rye B-chromosomes with the absence of both pairing suppressor (3A, 3D, 5B) and promotor (3B, 5A, 5D) chromosomes of common wheat (Triticum aestivum L.) is analyzed by comparison of pairing at Metaphase I of 27-, 27+2B, 28- and 28+2B-chromosome plants. These plants were obtained from crosses between the respective wheat monosomics (2n=41) and rye plants (Secale cereale L.) carrying or not carrying two B-chromosomes (2n=14 or 14+2Bs). —The effect of rye B-chromosomes on pairing depends on the function of the wheat chromosome which is absent in the appropriate hybrids, i.e., rye B-chromosomes have a suppressor effect on pairing when the pairing suppressing wheat chromosomes 3A, 3D or 5B are absent, while they behave as promotors when the pairing promoting chromosomes 3B, 5A or 5D are absent.     

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     

<Emphasis Type="Italic">Aegilops-Secale</Emphasis> amphiploids: chromosome categorisation,pollen viability and identification of fungal disease resistance genes

The aim of this study was to assess the potential breeding value of goatgrass-rye amphiploids, which we are using as a “bridge” in a transfer of Aegilops chromatin (containing, e.g. leaf rust resistance genes) into triticale. We analysed the chromosomal constitution (by genomic in situ hybridisation, GISH), fertility (by pollen viability tests) and the presence of leaf rust and eyespot resistance genes (by molecular and endopeptidase assays) in a collection of 6× and 4× amphiploids originating from crosses between five Aegilops species and Secale cereale. In the five hexaploid amphiploids Aegilops kotschyi × Secale cereale (genome UUSSRR), Ae. variabilis × S. cereale (UUSSRR), Ae. biuncialis × S. cereale (UUMMRR; two lines) and Ae. ovata × S. cereale (UUMMRR), 28 Aegilops chromosomes were recognised, while in the Ae. tauschii × S. cereale amphiploid (4×; DDRR), only 14 such chromosomes were identified. In the materials, the number of rye chromosomes varied from 14 to 16. In one line of Ae. ovata × S. cereale, the U-R translocation was found. Pollen viability varied from 24.4 to 75.4%. The leaf rust resistance genes Lr22, Lr39 and Lr41 were identified in Ae. tauschii and the 4× amphiploid Ae. tauschii × S. cereale. For the first time, the leaf rust resistance gene Lr37 was found in Ae. kotschyi, Ae. ovata, Ae. biuncialis and amphiploids derived from those parental species. No eyespot resistance gene Pch1 was found in the amphiploids.     

CYTOGENETIC AND EVOLUTIONARY STUDIES IN SECALE. I. SOME NEW DATA ON THE ANCESTRY OF S. CEREALE

Khush , G. S., and G. L. Stebbins . (U. California, Davis.) Cytogenetic and evolutionary studies in Secale. I. Some new data on the ancestry of S. cereale. Amer. Jour. Bot. 48(8): 723–730. Illus. 1961.—Cultivated rye, Secale cereale, was crossed with all 4 wild species of the genus. It crosses readily with S. montanum, S. africanum, and S. vavilovii, but crossability of S. cereale and S. silvestre is extremely low. Meiosis in the hybrid S. cereale × silvestre is characterized by high frequency of univalents at metaphase I, reduced chiasma frequency at metaphase I, high frequency of PMC's with unequal separations and laggards at anaphase I and II, high frequency of microspores with micronuclei, and extremely low pollen fertility. These abnormalities occurred less frequently in other hybrids, and consequently the pollen fertility is fairly high: 19.1% in the hybrid S. cereale × vavilovii and 31.3% and 31.8%, respectively, in the hybrids S. cereale × montanum and S. cereale × africanum. An interesting cytogenetic feature of all these hybrids, however, was the formation of a translocation configuration of 6 chromosomes at metaphase I of meiosis. In the hybrid, S. cereale × silvestre, a translocation configuration of 8 chromosomes was observed in a few cells. It is evident, therefore, that the genome of S. cereale differs from the genomes of wild species by 2 translocations. Another small translocation may differentiate S. cereale and S. silvestre, in addition. Thus, on the basis of chromosome arrangements, no particular wild species is most likely to be ancestral to S. cereale. Similarly, Stutz's hypothesis of hybrid origin of S. cereale seems highly improbable. After considering ecological preferences, breeding habits, geographical distribution, morphological and cytological affinities of wild species and cultivated rye, it is concluded that S. cereale evolved from S. montanum as a result of progressive cytological and morphological differentiation and that this differentiation was facilitated, probably, by adaptive superiority of translocation heterozygotes and rearrangement homozygotes.     

Study of a translocation in tetraploid rye

Colchicine induced tetraploids (4x=28) from diploidSecale cereale heterozygous for a translocation showed a strong tendency of non-preferential pairing for the interchanged chromosomes. The normal chromosomes associated in configurations up to quadrivalents, and the translocation complex formed multivalents up to octavalents. Most of the interchanged chromosome associations were characterized by their heteromorphic nature. The percentage of the chromosomes in the interchange complex forming multivalent associations was far higher than that of the remaining twenty chromosomes. Abnormalities were observed at anaphase I and II in the pollen mother cells. The tetraploids appeared to be completely sterile. It is suggested that the high frequency of multivalent formation may be explained on the basis that the interchange might have involved a region of localized chiasmata. The absence of polyploidy in the genusSecale as against its widespread occurrence in the related grass genera may be accounted for, in part, on the basis of non-preferential pairing.     

Chromosomal location of genes encoding low molecular weight prolamins from rye endosperm

Summary A group of proteins with similar Mr, isoelectric points and amino acid composition to those previously described for the low molecular weight prolamins (LMWP) of wheat and barley were isolated from the endosperm of rye (Secale cereale L.). Genes controlling four components of this protein group have been assigned to chromosome arm 4RL, through the two-dimensional electrophoretic analysis of T. aestivum-S. cereale disomic and ditelosomic addition lines. This observation, together with the previous assignment of LMWP genes in wheat to chromosome groups 4 and 7, is discussed in relation to the proposed 4R/7R chromosomes translocation in S. cereale.     

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.     

<Emphasis Type="Italic">Secale cereale</Emphasis> inter-microsatellites (SCIMs): chromosomal location and genetic inheritance

The polymerase chain reaction (PCR) was used to locate Secale cereale (inter-simple sequence repeat ISSR) or Secale cereale inter-microsatellite (SCIM) markers using wheat–rye addition lines in order to develop a set of molecular markers distributed on the seven rye chromosomes. The number of SCIM markers located on 1R, 2R, 3R, 4R, 5R, 6R and 7R chromosomes were 4, 3, 12, 3, 2, 9 and 8, respectively. Therefore, a total of 41 new SCIMs were located on the seven rye chromosomes. The segregation of the 63 different SCIM markers in three different F₂ was studied. The observed ISSR segregations were the 3:1 (50.7%), the 15:1 (12.7%) and the 1:1 (14.2%). The linkage analysis carried out indicated that seven of the segregating SCIMs were linked to chromosome 7R and two were linked to chromosome 4R. The use of the SCIM markers as a source of molecular markers that could be linked to interesting genes or other important agronomic traits is discussed.     

End-to-end chromosome attachments in mitotic interphase and their possible significance to meiotic chromosome pairing

Cytological studies on telophase and early prophase in roottip cells of several plant species (Allium cepa, 2n=16; four Crepis species, including Crepis capillaris, 2n=6; Callitriche hermaphroditica, 2n=6; Nigella arvensis, 2n=12; Secale cereale, 2n=14) revealed that chromosome ends are attached two by two forming chains of chromosomes (interphase associations). In these chains homologous chromosomes are presumably located adjacent to each other. In Crepis capillaris it was observed that the two nucleolar chromosomes form a separate ring one end attached to the ring of the four remaining chromosomes and the other end attached to the nucleolus. It is proposed that these end-to-end attachments have significance for chromosome pairing in meiosis. The adjacent location of homologous chromosomes in the interphase associations would facilitate rapid and regular synapsis.     

Biochemical evidence of a translocation between 6 RL/7 RL chromosome arms in rye (Secale cereale L.). A genetic map of 6R chromosome

Summary The segregation of different isozymic loci was investigated in backcrosses and F₂s in rye. The leucin aminopeptidase-1 (Lap-1), Aconitase-1 (Aco-1), Esterase-6 (Est-6), Esterase-8 (Est-8), and Endopeptidase-1 (Ep-1) loci were linked. The Aco-1, Est-6, and Est-8 loci have been previously located on the 6RL chromosome arm. The Lap-1 locus has been located on the 6RS chromosome arm. The results favor the gene order: Lap-1... (centromere)... Aco-1... Est-8... Est-6... Ep-1. The isoelectric focusing separations of aqueous extracts from mature embryo tissue of wheat-rye addition and substitution lines involving the chromosomes of cereal rye Secale cereale L. confirmed the gene location of locus Ep-1 on the 6RL chromosome arm. Screening of wheat-rye addition lines involving the chromosomes of Secale montanum revealed that Ep-1 locus is not located on chromosome 6R of S. montanum. These results are the first biochemical evidence of the translocation between chromosome arms 6RL/7RL in the evolution of S. cereale from S. montanum.     

Meiotic behaviour of Un,D and R genomes in the amphiploid Aegilops ventricosa -Secale cereale and the parental species

Summary Meiotic pairing frequencies of the Un and D genomes of Ae. ventricosa and the R of S. cereale could be easily established at metaphase I in Aegilops ventricosa — Secale cereale amphiploid plants as well as in its parental species by using the C-banding technique procedure. The results show a high diminution of chromosome pairing for all genomes in the amphiploid with respect to its parental species probably due to C-heterochromatin content and/or genotypic or cryptic interactions between the three genomes.     

Pairing Competition between Identical and Homologous Chromosomes in Rye and Grasshoppers

Meiotic pairing preferences between identical and homologous but not identical chromosomes were analyzed in spontaneous tetraploid/diploid chimeras of three male grasshoppers (Eyprepocnemis plorans) whose chromosome pair 11 were heterozygous for C-banding pattern and in four induced tetraploid/diploid chimaeral rye plants (Secale cereale) heterozygous for telomeric heterochromatin C-bands in chromosomes 1R and 2R. In the grasshoppers, a preference for identical over homologous pairing was observed, whereas in rye both a preference for homologous rather than identical pairing and random pairing between the four chromosomes of the set was found. From the results in rye, it can be deduced that pairing preferences do not depend exclusively on the similarities between chromosomes involved. It is suggested that genotypic or cryptic structural differences between the homologous chromosomes of each pair analyzed might be responsible for the pairing preferences found. This hypothesis can also explain the results obtained in grasshoppers, although the possibility of premeiotic association cannot be excluded in this material.     

Meiotic behaviour of telo-tertiary compensating trisomics of rye: evaluation for use in hybrid varieties

Summary Meiosis of four telocentric-tertiary compensating trisomics of rye (Secale cereale L.) was studied with the purpose of evaluating their suitability for use in maintaining genic male-sterile lines applied in hybrid varieties. They had been constructed from four different reciprocal translocations and three different telocentrics. In one trisomic a slight, but significant tendency was demonstrated for preferential pairing of the two normal chromosomes associated with the compensating complex. This promotes the desired segregation into one normal and one compensating karyotype. In all trisomies, however, too high a frequency of failure of chiasma formation in a critical segment of the complex was evident. This is correlated with the ease of recovery of the trisomics, but results in undesired segregational products. Interstitial chiasmata leading to the formation of branched configurations were also present, more in some trisomics than in others. These also result in undesired segregations. The behaviour at meiosis was so closely correlated with the length of the chromosome segments involved that a prediction of the most favourable combination of telocentric and translocation can be made. The telocentric should be large, the corresponding translocated segment large and the interstitial segment small. The non-translocated arm of the translocated chromosome should be large and the second translocated segment small. The combinations of translocations and telocentrics had not been selected for these criteria and did not meet the requirements for practical application.     

Genome-specific control of meiotic pairing evidenced in mutant Aegilops ventricosa-Secale cereale amphidiploids

Summary The Ae. ventricosa and S. cereale genomes were distinguished at meiosis by the C-banding procedure. Only two plants of the amphiploid Ae. ventricosa-S. cereale were found to exhibit the high degree of asynapsis limited to Aegilops ventricosa genomes. In addition, these genomes showed higher homoeologous pairing than homologous pairing frequencies. These results can be explained by the existence of separate genome-specific control of meiotic pairing between the chromosomes of both species in these synaptic mutant plants.     

Further insights on chromosomal pairing of autopolyploids: a triploid and tetraploids of rye

Chromosomal pairing of one triploid and three tetraploid plants of rye, Secale cereale, was analyzed by electron microscopy in surface-spread prophase I nuclei and compared with light microscopic observations of metaphase I cells. Prophase I is characterized by: (i) the weak alignment showed by the three or four unsynapsed or partially homologous synapsed axes; (ii) the low number ber of pairing partner switches (PPSs) displayed by both trivalents and quadrivalents; and (iii) the existence of complex multivalents in which up to 13 chromosomes in the triploid and 22 chromosomes in the tetraploids were involved. However, only few heterologous chromosomal associations were maintained at metaphase I. The results obtained are discussed under the assumptions of the random end pairing model with some modifications.     

Comparisons of the hybrids Hordeum chilensexH. vulgare,H. chilensexH. bulbosum,H. chilensexSecale cereale and the amphidiploid of H. chilensexH. vulgare

Summary Diploid hybrids between Hordeum chilense and three other species, namely H. vulgare, H. bulbosum and Secale cereale, are described together with the amphidiploid of H. chilensexH. vulgare. Both the diploid hybrid and the amphidiploid of H. chilensexH. vulgare were chromosomally unstable, H. chilensexH. bulbosum was less so, while H. chilensexS. cereale was stable. Differential amphiplasty was found in all combinations. No homoeologous pairing was found in the Hordeum hybrids but in H. chilensexS. cereale there was chromosome pairing both within the two genomes and between the genomes.     

Pairing Competition between Identical and Homologous Chromosomes in Autotetraploid Rye. I. Submetacentric Chromosomes

Meiotic pairing preferences between identical and homologous but not identical chromosomes were analyzed in ten induced tetraploid/diploid chimaeral rye plants (Secale cereale) heterozygous for telomeric heerochromatin C-bands in both arms of chromosome 1R. These plants were the progeny of two crosses between only one plant of cv. Petkus, used as male, and two plants of the inbred lines E and R, respectively. Different pairing preferences for chromosome 1R were found: (1) between plants, (2) between chromosome arms within the same plant and (3) between bivalents and multivalents within the same plant. The possible influence in the preferences of several factors such as differences in C-heterochromatin content in the chromosomes analyzed, specific genetic control and independence in pairing behavior between both arms and partner exchange is discussed.