Meiotic Stability Research Articles

Meiotic analysis of haploid and doubled haploid forms of Nicotiana otophora and N. tabacum.

Detailed meiotic studies were conducted on anther-derived haploids of Nicotiana otophora (n = 12) and N. tabacum (n = 24). At midpachytene stages the non-homologous chromosomes apparently remain unpaired. However, since the spreading of chromosomes at this stage was poor, the possible partial pairing, if any, between non-homologues could not be determined with certainty. One to two univalents rarely exhibited partial foldback pairing involving a single arm or the intercalary regions of the same chromosome. — At diakinesis the bivalent-like structures ranged from 0–2 in Otophora and 0–7 per cell in Tabacum haploids. The bivalent-like configurations (mostly rod types with chromatin connections of varying thickness) observed at meta-anaphase I varied from 0 to 1 and 0 to 5 per cell in haploids of Otophora and Tabacum respectively. The various types of secondary associations of univalents at meta-anaphase I were also studied in different haploids. — The probable origin and significance of bivalent-like configurations and secondary associations observed in Nicotiana haploids is briefly discussed. Based on our results, it is concluded that there is very little intra- or intergenomic pairing, if any, in Nicotiana haploids studied. — The meiotic behavior of chromosomes in doubled haploids (N. tabacum) obtained by leaf mid-rib culture, root culture and spontaneous chromosome doubling was remarkably regular with a stable chromosome number of 2n = 48. The meiotic stability of the doubled haploids permits using these materials directly in the breeding program.

IDENTIFICATION OF CHROMOSOMES CONTRIBUTING TO ANEUPLOIDY IN HEXAPLOID TRITICALE, CULTIVAR ROSNER

Detailed karyotype analyses were conducted on root-tip cells of aneuploid plants of hexaploid triticale, cultivar 'Rosner.' Although complete meiotic stability in this cultivar has not as yet been achieved, it currently represents the standard for triticale improvement in Canada. Rosner characteristically exhibits an average of 0.8 univalents per cell at metaphase I and approximately 10% of its progeny are aneuploid. The results of the present study clearly indicated that both wheat and rye chromosomes of the triticale complement contribute to the aneuploid condition, not primarily those of rye as believed earlier.

Cytomorphology of the Progeny of a Raw Allopolyploid in <i>Pennisetum</i>

A progeny of 210 plants raised from the selfed seeds of a raw allopolyploid (2n=42) of the parentage, Pennisetum typhoides (2n=14)×P. purpureum (2n=28) was analysed for variation. The method of metroglyph analysis was used. Segregants showing transgression in certain attributes over the values for the parental species were observed in the progeny as a consequence of genic segregation arising from the heterogenetic association of chromosomes of the constituent genomes. Inspite of fairly high degree of recombination, the population in general showed skewedness in distribution towards P. purpureum. There is a dominant bias for few attributes contributed by P. purpureum, while intermediate expression was observed for many others. The recombinants resembling amphiploid and P. purpureum occurred frequently. A cytological study of the progenies having pollen fertility ranging from 0 to 84 per cent has been made. The frequency of meiotic disturbances did not correspond to the extent of pollen sterility. The wide range of variation for pollen fertility in the progenies inspite of the meiotic stability and chromosome constancy points to the operation of genic factors controlling fertility. The role of cryptic structural hybridity in restoring recombinations and also in influencing the fertility-sterility status of the progenies has also been considered. The high meiotic stability of the progeny of the raw allopolyploid coupled with the facility for genic segregation is a welcome situation in the use of the hexaploids in back crossing programmes for improvement of the cultivated species.

A comparative study of the cytological and reproductive behaviour of wheat and triticale subjected to two temperature regimes

A comparison was made of the meiotic stability and reproductive behaviour ofTriticale hexaploide cv. Rosner andT. aestivum cv. Pitic in response to two temperature regimes (15° and 30°C) imposed continuously from premeiosis to maturity. Mean frequencies of MI open bivalents, univalents, and lagging chromosomes at AI were significantly higher in Rosner than in Pitic. Such irregularity would appear to arise from the asynchronous disjunction of chromosomes between Metaphase I and Anaphase I, resulting in meiotic disturbances and a high frequency of abnormal microspores. Despite such abnormalities, floret fertility was equivalent to that observed in Pitic, and the proportion of aneuploids recovered in the progeny, although greater than expected in wheat, was much lower than would be predicted. It is suggested that there is a strong certation effect in the transmission of aneuploid microspores and that the irregularities observed during microsporogenesis do not apply directly to megasporogenesis. No appreciable effect of temperature on meiotic chromosome behaviour during microsporogenesis was observed in either wheat or Triticale. In Triticale, high temperatures (30°C) substantially reduced spikelet fertility, and in contrast, low temperature (15°C) increased the frequency of aneuploids.

Meiosis and Fertility in Derivatives of AmphiploidPennisetum

SUMMARYA cytological study of progenies of amphiploid of P. typhoides × P. purpureum having pollen fertility ranging from 0 to 84 per cent has been made. It was found that meiotic disturbances did not correspond to the extent of pollen sterility and the plants showing less meiotic disturbances showed higher percentage of sterility than the plants with high disturbances. The wide range of variation of pollen fertility in the progenies inspite of the chromosome constancy and fairly high degree of the meiotic stability points to the operation of genic factors controlling fertility. The role of cryptic structural hybridity in influencing the fertility-sterility of the progenies has also been considered. It could be said that the sterility in amphiploid progenies is independent of the segregation for other morphological characters and also independent of genomic influence. The structural homology of the A and A' genomes of P. typhoides and P. purpureum was confirmed. The members of A and A' genome are largely undifferentiated in nature. The high meiotic stability of the hexaploid progenies coupled with genie segregation is a welcome situation in the use of the raw allopolyploid in breeding programmes.

Cytogenetic Effects and Responses of Agronomic Characters in Grain Sorghum (Sorghum vulgare Pers.) Following Atrazine Application1

Three varieties and two hybrids of grain sorghum were sprayed with atrazine at the rate of 2.7 kg a.i./ha (2.4 lb a.i./A). A single treatment was given to each plot and applications were made at weekly intervals, beginning 1 week after emergence. Pollen mother cells collected from each genotype treated at seven developmental stages were examined.Many affected microsporocytes were observed. Abnormalities consisted of multinucleate cells, bridges, and increased chromosome numbers, some of which were not a multiple of the basic number. Dyads and quartets often contained micronuclei. Atrazine treatment apparently interfered with meiotic stability regardless of time of application. Statistical analyses of grain yield, head weight, kernel weight, fertility, stalk diameter, and germination percentage indicated that treated groups did not differ from the control group. Plant height, however, differed between control and treated groups. No consistent relationship was observed between content of protein, soluble and total carbohydrates, and date of treatment. Also, no apparent relationship existed between frequency of chromosomal aberrations and agronomic responses following atrazine application.

A Cytological Study of Certain Autotetraploid Avena Hybrids1

Autotetraploid hybrids of Avena brevis ✕ A. hirtula, A. hirtula ✕ A. strigosa, and reciprocal were studied for cytological behavior, self‐fertility, and cross‐fertility in the C1 and C2 generations. There was no statistical difference between hybrids or generations for these characters. Cells with 10 bivalents and 2 quadrivalents were the most common type of chromosome pairing at metaphase I of meiosis. The overall means were .52 univalents, 9.86 bivalents, .33 trivalents, and 1.69 quadrivalents. Complete bivalent pairing was occasionally observed. When compared to data for autotetraploids of A. strigosa, the hybrids showed an increase of 4 to 5 bivalents, a decrease in multivalents, and about 20% higher self‐fertility.It was suggested that the increased meiotic stability of the autotetraploid hybrids was caused either by genic control of chromosome pairing or by cryptic structural differences between homologues from the As genomes of the parental species.

Inheritance patterns in hybrids between Sorghum almum Parodi and perennial sweet Sudan grass

Juicy stem and brown plant colour are mainly tetrasomically inherited in hybrids between Sorghum almum (2n = 40) and perennial sweet Sudan grass (2n = 40). Tetrasomic inheritance is also indicated for weak midrib development and dwarf habit. The juicy stem and brown plant colour characters are linked, and the chromosomes on which these genes are situated may pair preferentially and give a 15 : 1 segregation ratio, instead of pairing at random and giving a tetrasomic segregation ratio of 35 : 1. The capacity of these chromosomes to pair preferentially may be under genetic control. It is possible that preferential pairing is part of a general diploidization process, which has led to a reduction in quadrivalent formation and increased meiotic stability in the tetraploid sorghums.

A Study of the Meiotic Stability of Certain Agrotricum Hybrids1

Agronomy JournalVolume 46, Issue 8 p. 383-388 Article A Study of the Meiotic Stability of Certain Agrotricum Hybrids1 Harold G. Marshall, Harold G. MarshallSearch for more papers by this authorJohn W. Schmidt, John W. Schmidt Former Graduate Research Assistant and Assistant Agronomist, Kans. Agr. Exp. Sta., respectively.Search for more papers by this author Harold G. Marshall, Harold G. MarshallSearch for more papers by this authorJohn W. Schmidt, John W. Schmidt Former Graduate Research Assistant and Assistant Agronomist, Kans. Agr. Exp. Sta., respectively.Search for more papers by this author First published: 01 August 1954 https://doi.org/10.2134/agronj1954.00021962004600080007xCitations: 2 1 Contribution No. 499, Department of Agronomy, Kansas Agr. Exp. Sta., Manhattan, Kans. This study reports research submitted by the senior author in partial fulfillment of the requirements for the master's degree conferred May, 1953. AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat Citing Literature Volume46, Issue8August 1954Pages 383-388 RelatedInformation