Monosomic Series Research Articles

Cultivar Identification of a Monosomic Common Wheat Series

Storage proteins (gliadins) were employed in cultivar identification of a monosomic series produced on the basis of a Swedish cultivar. The cultivar was identified as Diamant 2.

Formation of New Original Material Based on the Genetic Heterogeneity of the Disomic Offspring of Aneuploid Wheat Plants

A series of disomic lines of spring wheat Opal developed on the basis of monosomic lines of this cultivar has been studied. The lines have been tested for combining ability, and the heterosis effect has been studied in disomic lines of F1 hybrids obtained by topcrossing. The line have been demonstrated to differ both from one another and from cultivar Opal in the expression of quantitative traits, combining ability, and the degree of heterosis in F1. These data suggest that recombinations accompanying the formation of the monosomic series have changed their genetic program. To test this suggestion, intramolecular heterogeneity of 42-chromosome plants has been analyzed using polymerase chain reaction (PCR) and isoenzyme analysis. The results confirmed the differences at the DNA and protein levels. According to the results of molecular analyses, A-genome lines are the most polymorphic. Strong heterosis effects have been detected in hybrid combinations contributed by D- and B-genome lines, which are characterized by medium and low degrees of molecular genetic polymorphism. Lines that are promising in terms of breeding programs have been identified.

Assignment of RFLP linkage groups to chromosomes using monosomic F1 analysis in hexaploid oat

The availability of molecular genetic maps in oat (Avena spp.) and improved identification of chromosomes by C-banding are two recent developments that have made locating linkage groups to chromosomes possible in cultivated hexaploid oat, 2n=6x=42. Monosomic series derived from Avena byzantina C. Koch cv Kanota and from Avena sativa L. cv Sun II were used as maternal plants in crosses with the parents, Kanota-1 and Ogle-C, of the oat RFLP mapping population. Monosomic F1 plants were identified by root-tip cell chromosome counts. For marker analysis, DNAs of eight F2 plants from a monosomic F1 were combined to provide a larger source of DNA that mimicked that of the monosomic F1 plant. Absence of maternal alleles in monosomic F1s served to associate linkage groups with individual chromosomes. Twenty two linkage groups were associated with 16 chromosomes. In seven instances, linkage groups that were independent of each other in recombination analyses were associated with the same chromosome. Five linkage groups were shown to be associated with translocation differences among oat lines. Additionally, the results better-characterized the oat monosomic series through the detection of duplicates and translocation differences among the various monosomic lines. The F1 monosomic series represents a powerful cytogenetic tool with the potential to greatly improve understanding of the oat genome.

Lr46: A Gene Conferring Slow-Rusting Resistance to Leaf Rust in Wheat

ABSTRACT Wheat (Triticum aestivum) cultivar Pavon 76 carries slow-rusting resistance to leaf rust that has remained effective in Mexico since its release in 1976. 'Pavon 76' was crossed with two leaf rust-susceptible wheat cultivars, Jupateco 73S and Avocet S, and between 118 and 148 individual F(2) plant-derived F(3) and F(5) lines were evaluated for adult-plant leaf rust resistance at two field sites in Mexico during different seasons. Evaluation of F(1) plants and parents indicated that the slow-rusting resistance was partially dominant. Segregation in the F(3) and F(5) indicated that the resistance was based on two genes with additive effects. Monosomic analysis was carried out to determine the chromosomal locations of the resistance genes. For this purpose, two or three backcross-derived cytogenetic populations were developed by crossing 'Pavon 76' with a monosomic series of adult-plant leaf rust-susceptible cultivar Lal-bahadur. Evaluation of such BC(2)F(3) and BC(3)F(3) lines from 16 confirmed 'Lalbahadur' monosomics indicated that one slow-rusting gene was located in chromosome 1B of 'Pavon 76'. This gene, designated as Lr46, is the second named gene involved in slow-rusting resistance to leaf rust in wheat.

Role of the Chromosome 4B in Suppressing Frost Resistance in Winter Wheat (Triticum aestivum L.)

SUMMARY Frost resistance of different monosomic lines were investigated under controlled environment conditions. In the case of Cheyenne, Mironovskaya 808 and Rannyaya 12 a reduction in the degree of frost resistance was observed when chromosomes 5A, 3B, 3A, 5B or 7A were missing. In two of the monosomic series there was also a drop in the level of frost resistance in monosomic lines 5D and 7B. The frost resistance of monosomic line 4B, on the other hand, was significantly better than that of the disome in two of the three cultivars. In previous experiments using substitution lines, the presence of a 4B chromosome originating from a variety with better frost resistance also led to an increase in frost resistance. The results suggest that a gene suppressor for frost resistance may be located on chromosome 4B

Chromosomal location of genes for supernumerary spikelet in bread wheat

The supernumerary spikelet (SS) character of bread wheat (Triticum aestivum L.) is an abnormal spike morphology expressing extra spikelets per spike. Chromosomal location of the genes for the SS character in the bread wheat line, Yupi Branching was determined by monosomic analysis. The normal-spiked bread wheat Chinese Spring monosomic series were used as testing lines. Data indicated that chromosomes 2D, 4A, 4B and 5A of bread wheat carry genes for SS character (bh genes). Among them, the gene on chromosome 2D has the strongest effect on the expression of the SS character. Comparison of disomic and monosomic plants in 2D, 4A, 4B and 5A F2 populations revealed that the bh genes are hemizygous-effective and dosage-independent. The F1 monosomic analysis showed that the bh genes of Yupi Branching are recessive.

Chromosomal location of genes for resistance to Puccinia striiformis in the wheat line TP1295 selected from the cross of Soissonais-Desprez with Lemhi

Crosses of a wheat line TP1295 with the cultivar Chinese Spring monosomic series were used to locate, on chromosome 1D, a major gene for resistance to isolate WYR 85-22 of race 6E0 of Puccinia striiformis. The gene is designated as Yr25 and is probably present in several of the cultivars currently widely used for differentiating races of this pathogen. The expression of the gene was modified by the environment and by at least one minor gene which may be located on chromosome 6A. In F2 and F3 generations from a cross between TP1295 and euploid Chinese Spring, a wide range of variation in infection type (IT) was observed. This precluded the classification of the plants as either resistant or susceptible, so they were assigned to 6 classes and analyzed by factorial correspondence analysis and non-hierarchical classification. When all F3 plants in a family were fully resistant, like TP1295 itself (IT ;), both Yr25 and the modifying gene were assumed to be present and homozygous. In environments favourable to expression of the gene, families thought to carry Yr25 alone had a distribution of ITs from fully resistant (IT ;) to intermediate (IT 2, rarely 3 or 3+). This F3 analysis indicated that use of IT data alone, in the monosomic analysis, would not reveal the chromosomal location of the genes and that chromosome counting of numerous plants was necessary. As well as indicating the chromosomes carrying the genes for resistance to isolate WYR 85-22, the data showed that plants monosomic for chromosomes 5B and 5D were more resistant than the corresponding disomics, indicating that these chromosomes promote susceptibility and supporting other evidence of the effects of these chromosomes on yellow rust resistance.

Characterization of ‘Sun II’ oat monosomics through C-banding and identification of eight new ‘Sun II’ monosomics

Monosomics are a powerful tool for genetic mapping in allopolyploid plant species such as oat (Avena sativa L., 2n=6x=42). A C-banded karyotype of the oat cultivar Sun II was compared with previously described oat karyotypes and was used to identify the missing chromosome in each line of Sun II aneuploids. These included new aneuploids, isolated among derivatives of oat haploids obtained from Sun II oat×maize crosses, along with the original Sun II aneuploid set which had been obtained by cytological screening of a Sun II population for spontaneous aneuploids. Eight new Sun II monosomics were identified among the derivatives of haploids from the oat×maize crosses, to give a total of 18 unique Sun II monosomic/nullisomic lines. All seven C-genome chromosomes are represented by Sun II monosomics. Chromosomes 13, 14 and 17 are not represented by Sun II aneuploids but are found in the Kanota monosomic series. Therefore, monosomics of some form are now available for all 21 oat chromosomes. A reciprocal translocation involving chromosomes 3C and 14, found in a portion of the original set of Sun II monosomic lines, was also described. No new translocations were detected in the Sun II×maize crosses.

The genomic identification of some monosomics of Avena sativa L. cv. Sun II using genomic in situ hybridization

Genomic in situ hybridization using total genomic DNA extracted from the C genome diploid species Avena eriantha (2n = 2x = 14, genome CpCp) was used to identify monosomics (2n = 6x − 1 = 41) of the constituent genomes of the hexaploid cultivated oat A. sativa L. cv. Sun II (2n = 6x = 42, genomes AACCDD). The results demonstrate 3 AD/C and 6 C/AD chromosome translocations, indicate that five of the missing monosomics are derived from the C genome, and show that there are duplicates within the partial monosomic series. Chromosome polymorphisms between some monosomic lines are also demonstrated.

Molecular genetic identification ofAvenachromosomes related to the group 1 chromosomes of the Triticeae

A collection of 19 wheat (Triticum aestivum) probes, detecting sequences in the seven homoeologous groups of chromosomes, were hybridized to DNA from the 'Kanota' series of oat monosomic lines (Avena byzantina) to investigate their use for identifying groups of homoeologous oat chromosomes. Three probes from homoeologous group 1 of wheat, psr161, psr162, and psr121, mapped among the set of oat chromosomes 1C, 14, and 17. One homoeologous group 6 probe, psr167, mapped to oat chromosomes 1C and 17. Two oat probes that had previously been shown to map to oat chromosomes 1C, 14, and 17 were then hybridized to DNA from the 'Chinese Spring' wheat ditelosomics. They localized to homoeologous group 1 wheat chromosomes, one to the short arm and one to the long arm. These results reveal that in hexaploid oat there is a group of three chromosomes that correspond at least in part to homoeologous group 1 of wheat. The remaining wheat probes identifying other wheat homoeologous sets did not detect a complete series of homoeologous chromosomes in oat. This was presumably due to the incomplete status of the 'Kanota' monosomic series, chromosomal rearrangement in Avena, weak hybridization signals owing to low probe-target sequence homology, and (or) detection of only two hybridization bands by the wheat probe.

Thinopyrum distichum addition lines: production, morphological and cytological characterisation of 11 disomic addition lines and stable addition-substitution line

Plants of the partial amphiploid Inia 66/Thinopyrum distichum (2n = 70)//Inia 66 (2n = 56) were used as male parents in crosses with the monosomic series in the common wheat cultivar Inia 66. The genome and homoeologous group of the monosomic used in the cross affected the distribution of chromosome number of the progeny plants in the F2 and F4. Meiosis in the pollen mother cells of the B1F7 partial amphiploids was not stable, and not different from that of the B1F1 in which univalents and multivalents were observed. Disomic addition lines were selected on the basis of morphology and meiotic stability in the F2, F4 and F5. Eleven of the fourteen possible wheat-Th. distichum disomic addition lines were identified using chromosome C-band pattern, as well as size and arm ratio, as genetic markers. Addition of T. distichum chromosome J (dll) produced a phenotype indicating homoeology with wheat group-2 chromosomes. Clear indications of homoeology based on morphological characteristics were not obtained in any of the other addition lines, probably due to the mixed homoeology of the Th. distichum chromosomes relative to wheat. The addition lines were all susceptible to leaf rust, unlike the germplasm-line Indis which carries a leaf rust resistance gene on a translocation segment derived from Th. distichum. Instability of meiotic pairing was observed in all addition lines. The stability, or not, of progeny chromosome counts did not reflect the level of chromosome pairing instability in the parental plants. SDS-PAGE for gliadin-type seed proteins revealed two addition lines which expressed seed storage proteins uncommon to Inia 66 but typical of Th. distichum.

Genetic control of amylose content in wheat endosperm starch and differential effects of three Wx genes

The endosperm starch of the wheat grain is composed of amylose and amylopectin. Genetic manipulation of the ratio of amylose to amylopectin or the amylose content could bring about improved texture and quality of wheat flour. The chromosomal locations of genes affecting amylose content were investigated using a monosomic series of Chinese Spring (CS) and a set of Cheyenne (CNN) chromosome substitution lines in the CS genetic background. Trials over three seasons revealed that a decrease in amylose content occurred in monosomic 4A and an increase in monosomic 7B. Allelic variation between CS and CNN was suggested for the genes on chromosomes 4A and 7B. To examine the effects of three Waxy (Wx) genes which encode a granule-bound starch synthase (Wx protein), the Wx proteins from CS monosomics of interest were analyzed using SDS-PAGE. The amount of the Wx protein coded by the Wx-B1 gene on chromosome arm 4AL was reduced in monosomic 4A, and thus accounted for its decreased amylose content. The amounts of two other Wx proteins coded by the Wx-A1 and Wx-D1 genes on chromosome arms 7AS and 7DS, respectively, showed low levels of protein in the monosomics but no effect on amylose content. The effect of chromosome 7B on the level of amylose suggested the presence of a regulator gene which suppresses the activities of the Wx genes.

Characterization of the hexaploid oat Avena byzantina cv. Kanota monosomic series using C-banding and RFLPs

The establishment of a C-banded karyotype of hexaploid oat (Avena spp., 2n = 6x = 42) has facilitated the cytological characterization of a monosomic series in 'Kanota', an A. byzantina (C. Koch) cultivar. The 'Kanota' series of monosomics analyzed in this study consists of only 12 of the 21 different chromosome-deficient lines possible plus potential translocated segments of two or three additional chromosomes. These findings were confirmed by RFLP mapping data from studies in which oat probes were assigned to syntenic groups using the 'Kanota' set of monosomic lines. Among the remaining nine monosomic lines analyzed, eight are missing chromosomes represented in the set of 12 unique lines and one line, monosomic K13, is missing a chromosome from the unique set of 12 that possesses a cytologically detectable translocation. This same translocation, involving chromosomes 7C and 14, is found in 5 of the 21 'Kanota' monosomics. The incompleteness of the set of 'Kanota' monosomics might be due to (i) difficulty in identifying individual oat chromosomes without C-banding, (ii) plant genotypic and phenotypic variability in the original source population of the 'Kanota' monosomics, and (or) (iii) a high frequency of monosomic shifts in progency of the original 'Kanota' monosomic lines.

Monosomic analysis of tissue culture response in wheat (Triticum aestivum L.)

The ability of immature embryos of wheat (Triticum aestivum L.) to respond in cell culture was examined in crosses between the 'Wichita' monosomic series and a highly regenerable line, 'ND7532'. Segregation in disomic controls and 13 monosomic families showed a good fit to a monogenic ratio indicating a qualitative mode of inheritance. Segregation in the cross involving monosomic 2D showed a high frequency of regeneration (93.6%) and high callus growth rate (1.87 g/90 days) indicating that 2D is a critical chromosome. Modifying genes may be located on other chromosomes. Substitution of chromosomes from a low regenerable cultivar 'Vona' further indicated that the group 2 chromosomes, in particular chromosome 2D, possess genetic factors promoting callus growth and regeneration.

Synaptic mutants in hexaploid oats (Avena sativa L.)

Three meiotic synapsis-deficient mutants of oats (Avena sativa L.) were analyzed to determine their inheritance pattern, detailed chromosomal behavior, and location to chromosome. These highly sterile mutants, one in the cultivar 'Stout' and two in 'Noble', had been recovered from progeny of sodium azide mutagenized populations. Each segregated as a single gene recessive. The only synapsis-deficient variants previously described in hexaploid oats have been nullisomics or ditelosomics. Mutant 'Stout 1212' was classified as asynaptic due to deficiencies in chromosome pairing at all meiotic stages. Mutants 'Noble 1362' and 'Noble 1911' were classified as desynaptic since their homologous chromosomes were paired in early meiosis but they disassociated prematurely in late prophase I. Using a partial monosomic series from the Welsh Plant Breeding Station, mutant 1212 was mapped to monosome XII and is probably a mutation in Syn-5, a gene previously defined only by its nulli effect. Mutants 1362 and 1911 were mapped to monosome IV and are probably mutations in Syn-1, a gene also previously defined only by its nulli effect. Seed set on the synaptic mutant plants in the field was less than 0.2% of that on fertile sibs and likely resulted from pollination by surrounding fertile plants. This seed may serve as a source of unique aneuploid stocks in oats.Key words: meiotic mutants, gene mapping, monosomics, nullisomics, oat cytogenetics.

Monosomic analysis of heading date and spikelet number in the common wheat (Triticum aestivum L.) multispikelet line ?Noa?

Genetic analysis of heading date and spikelet number was carried out in the common wheat (Triticum aestivum L.) multispikelet line 'Noa', by using the monosomic series of the regular line 'Mara'. 'Noa's' high number of spikelets was found to be controlled by a recessive major gene on chromosome 2D; a slight reduction in spikelet number was induced by another recessive gene on 'Noa's' 7A chromosome. 'Noa's' late heading date was found to be controlled by two recessive genes, located on chromosome 2D (a major effect) and 6B (a minor effect). The nature of the genes located on 'Noa's' 2D chromosome and the relationship between spikelet number and heading date are discussed.

Hybrid seed development and viability in crosses of T. aestivum (cv. Chinese Spring) monosomic lines with S. cereale

The diploid and tetraploid wheats have a crossing barrier that inhibits development and viability of the F1 hybrid seeds which result from their pollination with rye. This barrier is ineffective in synthetic or natural hexaploid wheat × rye crosses. From the results obtained by crossing the Chinese Spring monosomic series to a diploid rye composite, it was concluded that the breakdown of this barrier in hexaploid wheats is determined by polygenes, but may also involve genedosage effects. While more than half of the hexaploidwheat chromosomes may contribute to the breakdown of the barrier, chromosome 1D had the strongest effect. Its absence resulted in shrivelled and inviable hybrid kernels similar to those obtained when the T. durum cultivar Langdon was crossed with rye.

The chromosomal locations in wheat of genes conferring differential response to the wild oat herbicide, difenzoquat

SummaryF2, monosomic analysis involving crosses between the monosomic series of a resistant wheat variety, Chinese Spring, and a susceptible variety, Sicco, has located a major gene locus, designated Dfql, on chromosome 2B of wheat which determines the differential response of these varieties to treatment with the wild oat herbicide, difenzoquat. The allele from Chinese Spring conferring resistance is dominant and studies of the responses of Chinese Spring single chromosome substitution lines and nullisomic–tetrasomic lines for chromosome 2B indicate that this allele actively promotes resistance to the herbicide. It is suggested that this gene may prevent inhibition of DNA synthesis in the apical meristem, which is the site of action of the herbicide (Pallett & Caseley, 1980).Other chromosomes were also implicated as carrying ‘modifier genes’ which affect the ratio of resistant: susceptible plants in F2 monosomic families, namely 1D, 2D, 3A, 3B, 5B and 5D. These chromosomes may affect the retention and translocation of the herbicide to the target site and hence the threshold of response.The simple inheritance of difenzoquat resistance indicates that it should be easy by conventional breeding techniques to transfer the resistance into susceptible varieties.

Production and Reproductive Behavior of Monoploid Sugarbeet1

The rarity of sugarbeet (Beta vulgaris L.) monoploids has limited the usefulness of monoploids sugarbeet breeding. This study was conducted to evaluate the production and cytogenetical behavior of monoploid sugarbeets. The rate of occurrence of monoploids in three sugarbeet lines was 0.017%. Meiotic pairing in the monoploids indicated the presence of three or more duplications that involved at least six of the nine chromosomes in the basic genome. Chromosomes of monoploid sugarbeet usually were condense and seldom congregated at metaphase plates. Chromatid bridges and a centric fragments occurred in > 2% of microsporocytes. Only those gametes that developed from restitution nuclei and contained a complete set of sugarbeet chromosomes did not abort. Seed setting was rare, and not every monoploid sugarbeet produce viable seed. Sugarbeet monoploids gave rise to monoploid progeny through pollination with diploids at a rate of 1.49%, which was > 80 times higher than that from pollinating diploids. The progeny plants also contained 18, 19, 27, 36, and 18/36 chromosomes when monoploids were pollinated with diploids. A great majority (92.3%) of these progenies were diploids. The 19‐chromosome (trisomic) progeny was the only aneuploidy class recovered. It may not be possible to establish monosomic series of sugarbeet genotypes through conventiona pollination techniques because unbalance gametes (without an intact genome) do not survive. Although the monoploids exhibited morphologic dailvergence from diploid parents, the monoploid progeny resembled their respective maternal monoploids. This is the first reports howing the feasibility of recovering monoploid sugarbeet from monoploids.

Genetics of yellow berry in wheat (Triticum aestivum)

The inheritance of yellow berry, a grain disorder in durum and bread wheats, was studied in six intervarietal crosses in bread wheat. The trait was found to be controlled by either two or three dominant genes. Monosomic analysis using 'Chinese Spring' monosomic series showed the presence of two major dominant genes on chromosomes 1A and 7A, and four modifiers on 4A, 4B, 6A and 6D, which influence the expression of yellow berry in bread wheat.