Cytogenetic Analysis of Cotton Monosomics

Eleven monosomics in cotton that were obtained in the progenies of three disomic desynaptic plants were cytologically characterized. The transmission of the monosomes in progeny was shown in the 26 monosomic plants. In 23 plants the frequency of monosomics was ranged between 14.29 and 41.67 %. Three monosomics usually occurred in much lower frequencies (from 3.03 to 5.00 %). Various transmission rates indirectly pointed out different monosomes as a specific chromosomes of cotton genome. Three telochromosomes and one isochromosome were isolated from the progenies of the four monosomics. Using translocation test it was recovered that seven monosomes of different monosomics are homologous to one of the chromosomes of six translocation lines of our collection.     

The origin, identification, and plant morphology of five rice monosomics.

Five different monosomics of rice (Oryza sativa L.) were obtained by treatment of pollen with gamma irradiation, as a by-product of attempts to determine the cytological loci of certain marker genes, i.e., mature pollen carrying normal alleles at all loci was given gamma rays and used for pollinating strains that were homozygous for recessive marker genes. The monosomics showed distinguishable morphological features and had complete seed sterility. Cytological studies revealed that one monosomic was tertiary, the others primary. The tertiary monosomic was related to chromosome 10. Two primary monosomics for chromosomes 10 and 11 were identified. At metaphase I, the tertiary monosomic showed the chromosome configurations 1 III + 10 II, 11 II + 1 I, and 10 II + 3 I, and all primary ones showed the configuration 11 II + 1 I. All five monosomics showed very poor crossing ability and were not transmitted to the few progenies observed. A few trisomic plants were found in the progenies of a cross between monosomic and normal pollen in one monosomic. This is the first time that many monosomics in rice have been characterized. This information will be useful in studies of rice aneuploidy and cytogenetics. Key words : rice, monosomics, morphology, cytology, transmission, trisomics.     

THE ORIGIN,FERTILITY AND TRANSMISSION OF MONOSOMICS IN GOSSYPIUM

The origin of 51 monosomic plants in Gossypium hirsutum is described, and the great majority are shown to be fertile and transmissible. Both fertility and transmission rate can be increased by outcrossing and selection. Monosomics which have been isolated in a standard hirsutum background can be recognized by distinct morphological characteristics, including modifications of both vegetative and reproductive structures such as smaller or narrower leaves, smaller flowers or flower parts, and smaller, longer, or partially collapsed bolls. Monosomics involving the large chromosomes, i.e., the A genome, are recovered more frequently than are monosomics of the D (small chromosomes) genome. Furthermore, monosomics of certain of the A chromosomes are recovered more frequently than others. Of 20 identified hirsutum monosomics, 7 are chromosome A-2, 7 are A-4, 3 are A-6, and 1 each is A-1, D-17 and D-18.     

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. Received: 11 December 1996 / Accepted: 15 July 1997     

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.     

The origin,identification, and cytogenetic behavior of tomato monosomics

The missing chromosomal elements were cytologically identified in a primary monosomic (haplo-11) and 18 tertiary monosomics (lacking interchanged chromosomes) induced by radiation in the tomato. For the tertiary monosomics all interchanges occurred in the centromeres, and, as with single arms deficiencies in the same materials, deficiencies are tolerated for only 15 of the 24 arms of the complement. Non-homologous pairing was frequently observed in the univalent pachytene chromosomes. The monosomic condition was not transmitted to any of the 11,981 progeny of ten tested monosomics. Reproductive fertility and gross morphology were also studied.This research was supported in part by a grant (GM 06209) from the National Institutes of Health, U.S. Public Health Service.     

Identification of homoeologous chromosomes in hexaploid oat (A. byzantina cv Kanota) using monosomics and RFLP analysis

The use of RFLP markers, together with a partial set of monosomics available in Avena byzantina cv Kanota, has enabled us to identify putative homoeologous chromosome sets in hexaploid Avena species (2n = 6x = 42, AACCDD). We first identified probes producing distinct three-band patterns on Southern blots that possibly reflect orthologous loci of the three genomes present in the hexaploid. Using monosomic analysis, 51 different restriction fragments that hybridized to 26 probes were localized to 12 different chromosomes for which monosomic stocks were available. These DNA restriction fragments were localized to specific monosomics using image analysis to quantify band intensity relative to other bands in the same lane. From these data, we have tentatively identified two complete homoeologous sets of three chromosomes each and two partial sets of two of the three chromosomes. The results indicate that RFLP dosage analysis is useful in the characterization of homoeologous chromosomes in hexaploid oat where nullisomics for many of the chromosomes are not available.Mention of a trademark or proprietary product does not constitute a guarantee or warranty by the USDA-ARS or the University of Minnesota and does not imply approval over other products that also may be suitableJoint contribution of the Minnesota Agricultural Experiment Station and USDA-ARS. Scientific Journal Series Paper no. 20 650 of the Minnesota Agricultural Experiment Station     

Cytogenetic studies inClarkia,section primigenia. III. Cytogenetics of monosomics inClarkia amoena

Naturally occurring monosomic plants, with 13 instead of the usual 14 somatic chromosomes, have been found in several populations ofClarkia amoena subsp.huntiana (Onagraceae). These plants show no obvious phenotypic differences from their 14 chromosome sibs. Three types of meiotic pairing were found amongst 7 monosomic strains: 4 bivalents+chain of 4+univalent, 3 bivalents+chain of 4+chain of 3, and 2 bivalents+one heteromorphic rod bivalent+ring of 4+chain of 3. All are basically translocation heterozygotes of a peculiar kind composed of two genomes, one with 6, the other with 7 chromosomes. Both genomes can be transmitted through pollen and eggs, but because of the nature of the meiotic divisions, gametes with 6 chromosomes are in functional excess. Self-pollination of 5 of the monosomic strains does not give 12 chromosome nullisomic progeny. The nullisomics produced by the other 2 strains are weaker and later flowering than their 13 or 14 chromosome sibs, and are partially or completely sterile. The 6 chromosome genomes are hence usually inviable when homozygous. Crosses of the monosomics to a standard cytological strain, and intercrosses between monosomic strains, have allowed analysis of the end arrangements of chromosomes. Six different 7-chromosome genomes and 3 different 6-chromosome genomes have been identified. The translocation scheme proposed to account for the origin of the 6-chromosome genomes involves partition of most of the genetic material of one chromosome amongst two others plus the loss of a small centromere-bearing chromosome. This loss accounts for the lethality of the 6-genomes when homozygous. The fact that vigorous, healthy nullisomics are formed whenever two monosomics of different geographical origin are crossed indicates that the 3 monosomic genomes have had an independent origin, since they obviously complement one another's genetic deficiencies. The hybrid nullisomics are fairly fertile, and if formed in nature might serve as the starting point for a new race or species with a reduced basic chromosome number.     

Meiotic and isozymic characterization of plants regenerated from euploid and selfed monosomic tall fescue embryos

Summary Tissue culture of tall fescue (Festuca arundinacea Schreb., 2n=6x=42) would be enhanced by improving the callus induction and plant regeneration efficiency, and evaluating the meiotic and isozymic variation induced by culture. Mature embryos were cultured from four lines of Kenhy tall fescue and from the progeny of three selfed monosomics. Evaluation of six media-auxin combinations showed callus initiation was greatest on SH medium with 2.5 mg/l 2,4,5-T or 7.4 mg/l pCPA, while plant regeneration was greatest on SH medium with 0.5 mg/l 2,4-D. Cytological analyses of 27 plants derived from euploid parents showed a high frequency of aneuploidy (15/27). Chromosome numbers of aneuploids ranged from 36 to 41, with one plant having 80 chromosomes and two plants being asynaptic. Two of ten monosomic-derived plants were euploid, five were monosomic, one was monosomic with a fragment and two were double monosomic. Zymograms of the parents and regenerants were obtained for the enzymes ACPH, ADH, GOT, 6-PGD and PGI. Isozyme variation was observed for two groups of plants derived from the same Kenhy embryos. One group of four monosomic-derived plants differed for the enzymes GOT and ACPH, and all four plants had a PGI pattern. different from that of the parental monosomic plant. This indicated loss of a PGI allele, probably as a result of callus culture.Contribution No. 89-3-141 of the Kentucky Agricultural Experiment Station in cooperation with the USDA-ARS. Part of thesis research for senior author's M. S. degree     

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.     

Chromosomal Banding Analysis of Monosomics in Wheat

N-banding analysis has been used to identify the univalents of all 21 monosomics at diakinesis or metaphase Ⅰ. The univalents of nine wheat monosomics which are monosomic lB to 7B, 4A and 7A have shown distinctive N-banding patterns. These banding patterns appear to be identical in meiotic and mitotic chromosomes. The method is simple and speedy. The research probably provides a new way for cytological identification of monosomics in wheat and offers a technique for genome analysis of hybrids in wheat.     

DNA content of wheat monosomics at interphase estimated by flow cytometry

 Two complete, independently maintained sets of 21 monosomic wheat lines derived from cv. ‘Chinese Spring’ were analyzed for their DNA content at the G1 stage with flow cytometry. The DNA content of individual chromosomes was estimated by subtracting the value of a monosomic line from that of euploid wheat. Our data show that the estimated 2C DNA of individual wheat chromosomes in 21 monosomics at the G1 stage ranges from about 0.58 pg in chromosome 1D to approximately 1.12 pg in chromosome 3A. The A genome (2C=6.15 pg) seems to contain more DNA than the B (2C=6.09 pg) and D (2C=5.05 pg) genomes. Analysis of variance showed significant differences (α=0.01) in DNA content both among homoeologous groups and among genomes. Our estimates of interphase DNA content of wheat chromosomes from monosomic lines were poorly correlated to the chromosome sizes at metaphase (r=0.622, P≤0.01). This poor correlation might be due to differential coiling among chromosomes during cell division, possible bias of fluorochrome binding to heterochromatin, or heterogeneity among monosomic lines. Finally, flow cytometry may aid but cannot replace cytological checks in aneuploid maintenance. Received: 21 January 1997 / Accepted: 23 June 1997     

12057单体系及其二体抗旱生理指标的比较

利用１２０５７单体及其二体连续两年进行抗旱生理招标的比较,结果表明：１２０５７单体系珉春二体在灌浆中期旗叶相对含水量、细胞膜稳定性、叶片渗透势以及渗透调节能力等均存在差异。其中２Ｂ、３Ｂ、６Ｂ单体相对含水量较高;５Ａ单体叶组织膜稳定性较高;４Ｂ、５Ｂ、４Ｄ、６Ｂ、３Ａ单体的渗透势较低;６Ｂ、４Ｂ、３Ｂ、４Ｄ、、Ｂ单体的渗透调节能力较高。此外看出部分同源染色体群对上述生理招标的反应具有相似性。     

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. Received: 24 April 2000 / Accepted: 10 May 2000     

Developmental Capacity of Aneuploid Xenopus Species Hybrids

Diploid as well as triploid Xenopus interspecific hybrids generate aneuploid eggs because of the presence, at meiosis, of univalent chromosomes which are presumably distributed at random. Zygotes obtained from such eggs, fertilized by either normal or UV-irradiated sperm, were analysed for their developmental capacities. All monosomics die in the course of embryogenesis, whereby optimum capacities correspond closely with those observed in monosomic mammalian embryos, especially in mice. In contrast, hyperdiploid Xenopus are relatively viable: although many die exhibiting the'haploid syndrome'or various other abnormalities, 8% of them reach metamorphosis, and 1–2% become adults. Of the latter, the karyotype was established in 13 individuals. Among them, 8–16 supernumerary chromosomes were found to be present.     

Production of wheat–<Emphasis Type="Italic">Leymus racemosus</Emphasis> chromosome addition lines

We produced ten wheat–Leymus racemosus chromosome addition lines. Eight chromosomes (A, C, F, H, I, J, k, and l) were recovered as disomic additions and two (E and n) as monosomic. Screening of the addition lines was done by fluorescence in situ hybridization using several repetitive sequences as probes, which allowed us to identify different L. racemosus chromosomes and find many aberrant L. racemosus chromosomes. RFLP analysis revealed partial conservation of homology between L. racemosus and wheat chromosomes, depending on the homologous groups. Chromosomes A and l belonged to group 2, chromosomes C and I to group 5, and chromosome k to group 6. Chromosomes H and J were a mixture of groups 1, 3, and 7, chromosome n of groups 3 and 7, and chromosomes E and F were of group 4 and others. Comparison of our addition lines with other addition lines showed large cytological differences.Communicated by B. Friebe     

Cyto-Chromosomal Analysis of Developing Wheat Monosomics

In order to achieve the aim of advanced breeding program with the definite direction, it is necessary for us to develop the monosomic lines used for the wheat breeding programs in China. We fixed the wheat ears at appropriate stage in Carnoy’s fluid, and stained with acetocarmine in every generation from the different crosses mentioned above. According to their karyotypes of metaphase 1, the monosomics, normal bodies, monotelosomics, ditelosomics and allotypic bivalents were identified (Plate Ⅰ, 1–8). In the process of developing monosomic lines “Beijing Red No.1”, some monosomic lines such as 5A’s and 4D’s, can be directly proved by their phenotypes, other lines of monosomic 1B, 5B add 6B can also be directly proved to be true by their typical chromosomal morphology. In order to check the accuracy of chromosomal orders of monosomic lines, we tested all 21 monosomic lines of “Beijing Red No.1” by means of telosomic testing. At the same time we tested the origirnal monosomics of “Chinese Spring” as a check. In the F1’s of test crosses, those showing 20 bivalents and one monoelemic (20”+t’) were proved to be right. Whereas those showing 19 bivalents, 1 univalent and 1 allotypic bivalent (19”+1’+1’t’) were proved to be wrong. The karyotypes of F1’s from the test crosses for “Beijing Red No.1” can be verified by compairing with that of the check. During some years, we have examined 500 F1 plants of test crosses for monosomic lines of “Beijing Red No.1”, and some what less plants for monosomic lines of “Chinese Spring”. The number of observed cells usually was 100–200, the least was 40 and the most was 600. As the result, all F1's of test crosses showed accurate karyotypes. Besides detemning the F1 karyotypes of test crosses, we also analysed and compared their phenotypes with each other (photograph 9–12). According to the pbenotypes caused by the chang in chromosome number, structure and gene dosage, not only we can check the accuracy of testing result, but also locate the genes controlling some characters on the chromosomes or chromosomal arms.     

Selection of monosomic addition plants in offspring families using repetitive DNA probes in Beta L.

The distribution of two repetitive DNA probes Sat-121 and PB6-4, specific for the section Procumbentes of the genus Beta, was tested in 16 B. patellaris monosomic addition families using a dot-blot hybridization procedure. All monosomic additions were accurately distinguished from diploid sib plants with both DNA probes. The probe PB6-4, with the strongest signal after hybridization, was selected for rapid screening of an extensive number of putative monosomic additions in B. patellaris or B. procumbens addition families using a squash-blot hybridization procedure. The probe PB6-4 detected 118 monosomic additions in 640 plants (18.4%) in eight different B. procumbens addition families. The addition family with chromosome 4 of B. procumbens was semi-lethal and could not be tested. The distribution of PB6-4 in B. patellaris addition families was confirmed in 63 addition families using the squash-blot procedure. In 4580 plants of these addition families, 628 individual monosomic additions (13.7%) were found. The relationship of the morphological characteristics of monosomic addition plants to the results of the squash-blot hybridization (plants with signal) using probe PB6-4 is quite rigorous but not complete. The correlation between plants with a signal and chromosome number (2n=19) is complete. These results indicate that sequences present on PB6-4 are probably present on all chromosomes of B. patellaris and B. procumbens. The possibility of utilizing the sequence information of Sat-121 for a PCR-based assay to screen for putative monosomic addition plants was also investigated as an alternative to chromosome counting. The DNA-amplification profiles using the primers REP and REP.INV clearly distinguished monosomic addition plants from their diploid sibs.     

Isolation of Monosomics in Yeast

Tetraploid cultures of Saccharomyces cerevisiae triplex (A/A/A/a) at several loci were sporulated. All the diploid spores are expected to be homozygous (A/A) or heterozygous (A/a) and, hence, to have the dominant phenotype. Cells lacking one of the chromosomes (monosomics) may show the recessive phenotype (a/-). Therefore, spores that grew on complete medium but failed to grow on the relevant synthetic single-omission media were presumed to be monosomic. These isolates were further characterized by sporulation, and several stable monosomics were established.     

Developmental capacity of aneuploid Xenopus species hybrids.

Diploid as well as triploid Xenopus interspecific hybrids generate aneuploid eggs because of the presence, at meiosis, of univalent chromosomes which are presumably distributed at random. Zygotes obtained from such eggs, fertilized by either normal or UV-irradiated sperm, were analysed for their developmental capacities. All monosomics die in the course of embryogenesis, whereby optimum capacities correspond closely with those observed in monosomic mammalian embryos, especially in mice. In contrast, hyperdiploid Xenopus are relatively viable: although many die exhibiting the 'haploid syndrome' or various other abnormalities, 8% of them reach metamorphosis, and 1-2% become adults. Of the latter, the karyotype was established in 13 individuals. Among them, 8-16 supernumerary chromosomes were found to be present.