Morphology and cytology of the reciprocal hybrids between Elymus trachycaulus and Elymus canadensis

Genome ◽  
1990 ◽  
Vol 33 (1) ◽  
pp. 123-130 ◽  
Author(s):  
Taing Aung ◽  
P. D. Walton
Keyword(s):  
Chromosome Pairing ◽  
Low Frequency ◽  
Maternal Influence ◽  
Very High Frequency ◽  
Elymus Trachycaulus ◽  
Reciprocal Hybrids ◽  
Pistillate Parent ◽  
Hybrid Plants ◽  
Hand Pollination ◽  
Elymus Canadensis

Reciprocal hybrids between Elymus trachycaulus (2n = 4x = 28) and Elymus canadensis (2n = 4x = 28) were generated through emasculation and hand-pollination. All the F1 hybrid plants were tetraploids (2n = 28). The F1 hybrids were readily produced (9 plants from 150 pollinated florets; 6% success) in crosses where E. canadensis was used as the pistillate parent and the hybrid plants were produced directly from the apparently normal hybrid seeds. The percentage of hybrid plants produced was lower (7 plants from 400 pollinated florets; 1.7% success) in crosses where E. trachycaulus was used as the pistillate parent, and embryo culture procedures were necessary to recover plants from the shriveled seeds produced. Distinct morphological as well as cytological differences between the reciprocal hybrids were observed. All the F1 plants from each reciprocal cross more closely resembled their pistillate parent, indicating a strong maternal influence. Chromosome pairing at metaphase I showed a very high frequency of cells with a hexavalent configuration (69–81%) and a low frequency of cells with univalents (15–23%) in hybrids produced from crosses with E. canadensis as the pistillate parent. In all hybrids produced from crosses with E. trachycaulus as the pistillate parent, chromosome pairing showed a relatively low frequency of cells with a hexavalent (12–22%), while the frequency of cells with univalents was high (78–81%). Cytology of these hybrids indicates substantial control by cytoplasmic genes on chromosome pairing behavior. Reciprocal hybridization betwen octaploid E. trachycaulus (8x) and tetraploid E. canadensis (4x) plants yielded three 2n = 42, one 2n = 41, and one 2n = 39 hybrid plants. All plants were weak and sterile and more closely resembled the octaploid parent, although some intermediate characters were apparent.Key words: Elymus, reciprocal hybrids, maternal influence, cytoplasmic genes, chromosome pairing.

Intergeneric hybrids between Hordeum vulgare and Elymus trachycaulus resistant to Russian wheat aphid

Genome ◽  
1991 ◽  
Vol 34 (6) ◽  
pp. 954-960 ◽  
Author(s):  
Taing Aung
Keyword(s):  
Hordeum Vulgare ◽  
Chromosome Pairing ◽  
Chromosome Doubling ◽  
Nuclear Gene ◽  
Russian Wheat Aphid ◽  
Intergeneric Hybrids ◽  
Hordeum Vulgare L ◽  
Elymus Trachycaulus ◽  
Hybrid Plants ◽  
Slender Wheatgrass

Intergeneric hybrids between cultivated barley (Hordeum vulgare L.) (2n = 2x = 14) and slender wheatgrass (Elymus trachycaulus (Link) Gould ex Shinners), PI 531691 (2n = 4x = 28), were produced. This slender wheatgrass accession carries resistance to Russian wheat aphid, Diuraphis noxia Mordvilko, and was used as pollen parent. The seven hybrid plants were also resistant to Russian wheat aphid. The hybrids were produced at a frequency of 0.21% of emasculated and hand-pollinated florets. Chromosome pairing in all the euploid hybrids was very low (average chiasma frequency per cell, 0.30). This indicates that the I genome from H. vulgare is remotely related to the SH genomes of E. trachycaulus. Expression of resistance to Russian wheat aphid in all the hybrid plants demonstrates that the nuclear gene or genes for insect resistance contributed by E. trachycaulus are either dominant or hemizygous effective. Five of the seven hybrid plants were vigorous and produced well-developed flowering spikes; however, they did not shed viable pollen. Since all the vegetatively cloned plants of these hybrids exhibited a high degree of perennial characteristics and could be induced to flower under a favourable light and temperature regime, they appear congenial for chromosome doubling and backcrossing. Preliminary observations suggest that successful backcrossing could be achieved using the F1 hybrids as pistillate parent and H. vulgare as pollen parent.Key words: Russian wheat aphid resistance, intergeneric hybrids, genomic relationship, chromosome pairing, Hordeum vulgare, Elymus trachycaulus.

scholarly journals Peranan Lingkungan Sosial terhadap Pembentukan Karakter Peduli Lingkungan Mahasiswa Pendidikan Geografi di Universitas Samudra Langsa

2018 ◽  
Vol 10 (2) ◽  
pp. 235
Author(s):  
Fitria Mustika ◽  
Tengku Muhammad Sahudra
Keyword(s):  
Family Environment ◽  
High Frequency ◽  
Low Frequency ◽  
Measurement Scale ◽  
Education Student ◽  
Achievement Level ◽  
Very High Frequency ◽  
Environmental Care ◽  
The Family

This study aims to determine the role of the family, community, and tertiary environment towards the formation of caring character in the geography education student environment. The output of this study was a four-indexed indexed education journal and a UNIMED google scolar. Samples from the study population were 20 respondents with 30 items about questionnaires. The time of the study starts from May 2018 to October 2018. The measurement scale in this study is the scale of the briquette. Data collection by means of library studies, interviews, questionnaires, and documentation. This research was conducted by distributing questionnaire questionnaires and interviews. Based on the results of questionnaire data processing, the family environment has a very high frequency in the formation of character of the student's environmental care with an achievement level of a total score of 91%. Furthermore, the role of the campus environment also has a high frequency in the formation of the character of the student's environmental care with a total score of 89%. Whereas the family environment has a low frequency in the formation of character of student environmental care with a total score of 57%. It can be concluded that the family environment has the most role in forming the character of the student's environmental care.

Suppression of homologous pairing between chromosomes of A and B genomes of 4x and 6x wheats by Hordeum californicum Covas and Stebbins

Genome ◽  
1988 ◽  
Vol 30 (1) ◽  
pp. 8-11
Author(s):  
H. S. Balyan ◽  
G. Fedak
Keyword(s):  
Chromosome Pairing ◽  
Chinese Spring ◽  
Chiasma Frequency ◽  
Mother Cell ◽  
Triticum Turgidum ◽  
Regulatory Gene ◽  
Intergeneric Hybrids ◽  
Homologous Pairing ◽  
Meiotic Analysis ◽  
Hybrid Plants

Three hybrids of Triticum turgidum cv. Ma with Hordeum californicum × T. aestivum cv. Chinese Spring amphiploid were obtained at a frequency of 1.6% of the pollinated florets. Meiotic analysis of the hybrid plants revealed an average chiasma frequency per pollen mother cell ranging from 15.27 to 17.60. The lower than expected chromosome pairing in the hybrid plants was attributed to the suppression of pairing between homologous wheat chromosomes by pairing regulatory gene(s) in H. californicum.Key words: intergeneric hybrids, Hordeum californicum, Triticum turgidum, meiosis, chromosome pairing.

Immunotherapeutic strategies: the melanoma example

Immunotherapy ◽  
2009 ◽  
Vol 1 (4) ◽  
pp. 679-690
Author(s):  
Annelies Jorritsma ◽  
Ton NM Schumacher ◽  
John BAG Haanen
Keyword(s):  
T Cell ◽  
Adoptive Immunotherapy ◽  
Low Frequency ◽  
Cell Repertoire ◽  
Very High Frequency ◽  
In Vitro Expansion ◽  
Clinical Responses ◽  
Application Potential ◽  
T Cell Transfer

T-cell-based immunotherapy can be induced by nonspecific activation, by antigen-specific immunization, or by adoptive immunotherapy. In this review, progress in these areas is discussed as based on data from clinical trials for the treatment of metastatic melanoma. Nonspecific immunotherapy has been shown to result in low, but in some cases significant, levels of objective tumor responses, and is often associated with autoimmune reactions. Antigen-specific targeting of tumors via vaccination has only resulted in low to very low levels of objective responses, and these strategies seem to have most value when the T-cell repertoire is not affected by tolerance. Finally, adoptive immunotherapy can be applied by in vitro expansion of autologous lymphocytes that have escaped tolerance or by genetic transfer of allogeneic T-cell receptors (TCRs). Autologous adoptive T-cell transfer has resulted in a very high frequency of clinical responses when combined with chemotherapy and IL-2 administration in single-center studies. Although TCR gene transfer has, until now, only resulted in a low frequency of clinical responses, it does have a broader application potential, and optimization of this strategy is likely to improve its efficacy.

Tetrasomic inheritance and chromosome pairing behaviour in the naturally occurring autotetraploid Heuchera grossulariifolia (Saxifragaceae)

Genome ◽  
1989 ◽  
Vol 32 (4) ◽  
pp. 655-659 ◽  
Author(s):  
Paul G. Wolf ◽  
Pamela S. Soltis ◽  
Douglas E. Soltis
Keyword(s):  
Chromosome Pairing ◽  
Meiotic Chromosome ◽  
Low Frequency ◽  
Small Chromosome ◽  
Tetrasomic Inheritance ◽  
Naturally Occurring ◽  
Chromatid Segregation ◽  
Marker Loci ◽  
Allozyme Loci ◽  
Pairing Behaviour

Inheritance patterns at four allozyme loci and chromosome pairing behaviour at diakinesis were examined in the naturally occurring autotetraploid Heuchera grossulariifolia. Segregation patterns for Tpi, Pgi, Pgm-2, and Lap deviated significantly from all possible disomic models. All patterns were consistent with tetrasomic inheritance of these marker loci. No chromatid segregation was detected electrophoretically. Meiotic chromosome configurations at diakinesis in 45 cells were compared with a previously published model to test for autopolyploid-like chromosome pairing. Using the observed chiasma frequencies, the frequency of quadrivalents was consistent with the expectations for an autotetraploid. We suggest that the low frequency of quadrivalents at diakinesis in Heuchera grossulariifolia is due to small chromosome size, which results in a low chiasma frequency.Key words: autopolyploidy, tetrasomic inheritance, chromosome pairing, isozyme genetics, Heuchera.

EFFECT OF RYE ON HOMOEOLOGOUS CHROMOSOME PAIRING IN WHEAT × RYE HYBRIDS

1977 ◽  
Vol 19 (3) ◽  
pp. 549-556 ◽  
Author(s):  
J. Dvořák
Keyword(s):  
Triticum Aestivum ◽  
Chromosome Pairing ◽  
Chinese Spring ◽  
Triticum Aestivum L ◽  
Homoeologous Chromosome ◽  
Wheat Genotype ◽  
Hybrid Plants ◽  
Homoeologous Chromosome Pairing ◽  
Secale Cereale L ◽  
Polygenic System

The number of chiasmata per cell at metaphase I was scored in eight haploid plants of Triticum aestivum L. emend. Thell. cv. 'Chinese Spring' and 100 hybrid plants of Chinese Spring × Secale cereale L. Mean chiasma frequency per cell ranged from 0.00 to 3.59 in the hybrids and from 0.17 to 0.35 in the haploids. Since the same wheat genotype was present in both the haploids and hybrids, it is concluded that some of the rye genotypes promoted homoeologous chromosome pairing. The absence of distinct segregation classes among the hybrids suggests that these genes constitute a polygenic system.

Exploiting the characteristics of volcanic lightning for volcano monitoring

2020 ◽  
Author(s):  
Sonja Behnke ◽  
Harald Edens ◽  
Seda Senay ◽  
Diana Swanson ◽  
Alexa Van Eaton ◽  
...  
Keyword(s):  
Radio Frequency ◽  
Long Range ◽  
Detection Efficiency ◽  
Low Frequency ◽  
Volcano Monitoring ◽  
Volcanic Plume ◽  
Very High Frequency ◽  
New Information ◽  
Lightning Discharges ◽  
Volcanic Lightning

<p>Volcanic lightning measurements are gaining momentum in the volcano monitoring community as a tool to identify when an ash producing eruption has occurred. As a volcanic plume develops from an ash-laden jet to a convective plume, the electrical discharges also evolve, ranging from small “vent discharges” (a few meters in length) and near-vent lightning (tens of meters to kilometers in length) to thunderstorm-like plume lightning (tens of kilometers in length). Currently, volcanic lightning monitoring capabilities for volcano observatories are mainly limited to using long-range lightning sensor networks, which do not detect the full gamut of volcanic lightning due to the networks’ detection efficiency and the radio frequency band that they use (very low frequency or low frequency). This biases the sensors towards detecting only the larger volcanic lightning discharges that occur at later stages in plume development, which can result in detection delays of minutes to tens of minutes from the onset of eruption. In addition to the latency, there is no way to know if the lightning picked up by long range networks is from a volcanic or meteorological source without some other additional source measurement. Both the latency and the source ambiguity could be reduced by using lightning sensors at close range that can detect the very small vent discharges associated with volcanic explosions. Vent discharges occur within the gas thrust region in a plume, starting simultaneously with the onset of an eruption and persisting continually for seconds or tens of seconds, depending on the duration of an eruption. They produce a distinctive ‘continual radio frequency’ signal, of which there is no analogous signature in meteorological lightning. Thus, the characteristics of the radio frequency signature of vent discharges could be exploited to innovate a new sensor design that is both low power and transmits information (i.e., a useful derived data product) at rates low enough to be used at remote volcanoes where volcano monitoring is often sparse. To meet this goal, a new experiment at Sakurajima Volcano in Japan is underway to learn more about the physical characteristics and signal characteristics of vent discharges. We use broadband very high frequency sensors to record time series measurements of the vent discharges and other volcanic lightning discharges that occur from explosions of the Minamidake crater of Sakurajima. These measurements reveal new information about vent discharges, such as their duration and spectral features, that can be used to help identify when explosive eruptions are occurring.</p>

Investigating Thunderstorm HF/VHF Radio Bursts with Weak Lower Frequency Radiation

2020 ◽  
Author(s):  
Ningyu Liu ◽  
Joseph Dwyer
Keyword(s):  
High Frequency ◽  
Large Scale ◽  
Strong Field ◽  
Large Fraction ◽  
Low Frequency ◽  
Very High Frequency ◽  
Lightning Initiation ◽  
Study Support ◽  
Volcanic Lightning ◽  
Frequency Radiation

<p>While the spectrum of lightning electromagnetic radiation is known to peak around 5-10 kHz in the very low frequency (VLF) range, intense high frequency/very high frequency (HF/VHF) radiation can be produced by various lightning related processes. In fact, thunderstorm narrow bipolar events (NBEs), which are capable of initiating lightning, are the most powerful HF/VHF sources in nature on Earth. But even for NBEs, the spectral intensity in HF/VHF is still many orders of magnitude weaker than that of lower frequencies (Liu et al., JGR, 124, https://doi.org/10.1029/2019JD030439, 2019). HF/VHF bursts with weak VLF signals, however, can also be produced by thunderstorms. These bursts may be related to the thunderstorm precursor events noted by Rison et al. (Nat. Commun., 7, 10721, 2016) and are also found to precede a large fraction of lightning initiation (Lyu et al., JGR, 124, 2994, 2019). They are also known as continual radio frequency (CRF) radiation associated with volcanic lightning (Behnke et. al., JGR, 123, 4157, 2018).</p><p> </p><p>In this talk, we report a theoretical and modeling study to investigate a physical mechanism for production of those HF/VHF bursts. The study is built on the theory developed recently concerning the radio emissions from an ensemble of streamers (Liu et al., 2019). We find an ensemble of streamer discharges that develop in random directions can produce HF/VHF radiation with intensity comparable to those all developing in a single direction, but the VLF intensity is many orders of magnitude weaker. The results of our study support the conclusions of Behnke et. al (2018) that CRF is produced in the absence of large-scale electric field, it results in insignificant charge transfer, and it is caused by streamers. In the context of the HF/VHF bursts preceding lightning initiation (Lyu et. al, 2019), our results imply that highly localized strong field regions exist in thunderstorms and streamers take place in those regions, which somehow precondition the medium for lightning initiation.</p>

Chromosome Pairing in Reciprocal Hybrids ofSolanum IntegrifoliumandS. IndicumVar.Multiflora

Caryologia ◽  
1980 ◽  
Vol 33 (2) ◽  
pp. 289-294 ◽  
Author(s):  
P. B. Kirti ◽  
B. G. S. Rao
Keyword(s):  
Chromosome Pairing ◽  
Reciprocal Hybrids

Cytology of triploid and pentaploid hybrids of Elymus trachycaulus × Pseudoroegneria spicata and P. spicata ssp. inermis

Genome ◽  
1987 ◽  
Vol 29 (3) ◽  
pp. 470-480 ◽  
Author(s):  
Taing Aung ◽  
P. D. Walton
Keyword(s):  
Low Frequency ◽  
Plant Size ◽  
Double Dose ◽  
Homoeologous Pairing ◽  
Pseudoroegneria Spicata ◽  
Elymus Trachycaulus ◽  
Chromosome Associations ◽  
Size Variability ◽  
High Degree ◽  
Very High

Emasculated clones of tetraploid and octaploid Elymus trachycaulus crossed with Pseudoroegneria spicata yielded 69 triploids and 13 pentaploid hybrids. The triploid hybrids were morphologically intermediate between the parental species but the pentaploid hybrids resembled E. trachycaulus more closely than P. spicata. A very high degree of plant size variability (very weak to very vigorous) was observed among the 50 triploids that survived to maturity. The variability among the pentaploids, though apparent, was not high. Mean chromosome associations among the selected eight triploids varied from low multivalent formation at meiosis (7.60 I + 6.18 II + 0.24 III + 0.08 IV) to high multivalent-forming meiosis (7.28 I + 5.66 II + 0.32 III + 0.36 IV). The bivalent configurations in these triploids were attributed to homoeologous pairing between the S1 genome of P. spicata and S genomes of E. trachycaulus and the multivalents indicated intergenomal and intragenomal pairings. Mean chromosome associations of 5.22 I + 11.94 II + 1.97 III in 78.7% and 7 I + 14 II in 21.3% of the 150 cells were distributed among the three pentaploid hybrids. The low frequency of trivalents and the absence of multivalents higher than trivalent configurations suggest that homoeologous pairing was substantially reduced and there was no intergenomal and intragenomal pairing in these 2n = 35 x hybrids. Fourteen triploids and three pentaploid hybrids were produced from 4x and 8x forms of E. trachycaulus and P. spicata spp. inermis crosses. The triploids were intermediate between the parents but the pentaploids were more similar to E. trachycaulus. Mean chromosome associations in the triploids (6.020 I + 5.315 II + 0.554 III + 0.235 IV + 0.250 V + 0.048 VI + 0.03 VII) and in the pentaploids (3.50 I + 10.18 II + 3.54 III + 0.13 IV) indicated a very high degree of intergenomal and intragenomal pairing in the triploids; nevertheless, it was greatly reduced in the pentaploids. The Pseudoroegneria spicata ssp. inermis genome may have gene(s) that affect a high degree of intergenomal and intragenomal pairing in triploid hybrids with E. trachycaulus. However, in pentaploid hybrids (SS HH S2) the S and H genomes of E. trachycaulus in double dose seem to have restored its regular meiotic bahaviour, at least partially, and reduced homoeologous pairing as well as intergenomal and intragenomal pairing. Key words: Elymus trachycaulus, Pseudoroegneria spicata, regular meiotic behaviour, double dose, intergenomal pairing, intragenomal pairing.

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