摘要:

Three meiotic synapsis-deficient mutants of oats (Avena sativaL.) 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 inSyn-5, a gene previously defined only by its nulli effect. Mutants 1362 and 1911 were mapped to monosome IV and are probably mutations inSyn-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.

ISSN:0831-2796    

DOI:10.1139/g88-001

出版商:NRC Research Press    

年代:1988

数据来源: NRC

摘要:

Three hybrids ofTriticum turgidumcv. Ma withHordeum californicum×T.aestivumcv. 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) inH.californicum.Key words: intergeneric hybrids,Hordeum californicum,Triticum turgidum, meiosis, chromosome pairing.

ISSN:0831-2796    

DOI:10.1139/g88-002

出版商:NRC Research Press    

年代:1988

数据来源: NRC

摘要:

Crosses heterozygous for the virulence locusTox1show a high frequency of nonrandom ascospore abortion, in addition to a high frequency of random abortion seen in homozygous crosses. In crosses among closely related laboratory strains, the frequency of asci with eight mature, viable spores dropped from 35–47% of asci with mature spores in crosses homozygous forTox1to 3–17% in heterozygous crosses. Segregation for alternate alleles ofTox1was 2:2 in 98% of asci with four viable spores. Patterns of abortion in crosses involving field isolates were similar to the patterns in crosses among laboratory strains. No recombinants betweenTox1and the abortion-inducing factor were detected among 112 progeny of laboratory strains. The results suggest that race T (TOX1) and race O (tox1) strains ofC.heterostrophusdiffer by a chromosome rearrangement, possibly a reciprocal translocation, with a breakpoint at or nearTox1.Key words: fertility, T-toxin,Cochliobolus heterostrophus,Helminthosporium maydis,Bipolaris maydis,Drechslera maydis, chromosome rearrangement, reciprocal translocation.

ISSN:0831-2796    

DOI:10.1139/g88-003

出版商:NRC Research Press    

年代:1988

数据来源: NRC

摘要:

Interference between metaphase I associations (bonds) in specific segments of the chromosomes involved in translocation T242W of rye has been studied. Different values of coincidence were obtained at mid- and late metaphase I for all segment pairs analyzed. At mid-metaphase I there is negative interference between segments opposite to the translocation breakpoint and there is no cross-centromere interference. At late metaphase I there is negative interference in all these segment pairs. The comparison between mid- and late metaphase I cells also indicated that the frequency with which some of these segments are associated decreases along this stage. The possible causes of this decrease and its relation to the differences in coincidence estimates are discussed.Key words:Secale cerealeL., translocations, chiasma interference.

ISSN:0831-2796    

DOI:10.1139/g88-004

出版商:NRC Research Press    

年代:1988

数据来源: NRC

摘要:

Southern analysis of 19Adhnull activity alleles isolated from Tasmanian populations ofDrosophila melanogasterhave shown that there are no detectable insertions or deletions in an 11.8-kb region that contains the gene. Northern blot analyses of the null alleles have shown that they all produce a transcript about 100 bases longer than that produced by the normal allele and they accumulate a precursor of 1800 bases. The amount of the major transcript produced by the null alleles is about 10% of that produced by normal alleles. The molecular properties of the null alleles suggest that they share a common origin.Key words: alcoahol dehydrogenase, null alleles, mRNA,Drosophila melanogaster.

ISSN:0831-2796    

DOI:10.1139/g88-005

出版商:NRC Research Press    

年代:1988

数据来源: NRC

摘要:

Two small-sized and two large-sized male pink salmon (Oncorhynchus gorbuscha) were mated to each of four females, producing eight families sired by small males and eight sired by large males. The juveniles were reared for 500 d after fry emergence. Juvenile weight in the two male size classes was similar until the spring of the year of maturity, when juveniles sired by large males grew faster than those sired by small ones. Heritability estimates of weight based upon the dam component of variance increased during 500 d of rearing from 0.4 to 0.8. Heritability of weight based upon the sire component of variance generally ranged between 0.1 and 0.3. The large variation in male body size in spawning pink salmon populations may have resulted from different male breeding strategies.Key words: heritability, salmon, body size.

ISSN:0831-2796    

DOI:10.1139/g88-006

出版商:NRC Research Press    

年代:1988

数据来源: NRC

摘要:

To help elucidate the origin of the B genome in polyploid wheats, karyotypes ofTriticum turgidum,Triticum monoccum, and all six purported B genome donors were compared. The analysis utilized a common cytological procedure that employed the most advanced equipment for the measurement of chromosome lengths at metaphase in root tip cells. A comparison of the karyotypes ofT.turgidumandT.monococcumpermitted the identification of B genome chromosomes ofT.turgidum. These consist of two SAT pairs, one ST pair, three SM pairs, and one M pair of homologues. Comparisons of the chromosomes of the B genome ofT.turgidumwith the karyotypes of the six putative B genome donors showed that only the karyotype ofAegilops searsiiwas similar to the one deduced for the donor of the B genome inT.turgidum, suggesting thatAe.searsiiis, therefore, the most likely donor of the B genome to the polyploid wheats. Support for this conclusion has been derived from geographic, DNA-hybridization, karyotype, morphological, and protein data reported since 1977. Reasons why the B genome donor has not been unequivocally identified are discussed.Key words: phylogeny, karyotypes,Triticum turgidum,Triticum monococcum, B genome, B genome donors.

ISSN:0831-2796    

DOI:10.1139/g88-007

出版商:NRC Research Press    

年代:1988

数据来源: NRC

摘要:

The pattern of chromosomal pairing was analyzed in male deer mice (Peromyscus maniculatusandPeromyscus sitkensis) heterozygous for the presence of heterochromatic short arms. G- and C-banding of somatic metaphases indicated that the presence of heterochromatic short arms increased the length of chromosome 4 by 15% inP.sitkensisand that of chromosome 8 by 9% inP.maniculatus. Analysis of silver-stained late zygotene and early pachytene nuclei revealed a low frequency of unequal axial lengths in the synaptonemal complexes corresponding to the heteromorphic bivalents. All mid- and late pachytene nuclei, however, exhibited fully paired synaptonemal complexes with equalized axial lengths. These observations suggest the existence of an adjustment mechanism which functions to equalize the lengths of the two axes of the heteromorphic synaptonemal complex.Key words: synaptonemal complex,Peromyscus, heterochromatin, chromosomal polymorphism, synaptic adjustment.

ISSN:0831-2796    

DOI:10.1139/g88-008

出版商:NRC Research Press    

年代:1988

数据来源: NRC

摘要:

G-banding was successfully demonstrated in chromosomes of culturedVicia hajastanacells using a simple and reproducible technique. The factors considered important in achieving successful banding were (i) the omission of HCl hydrolysis or enzymatic digestion during the process of making the chromosome preparations; and (ii) the treatment with a weak NaHCO3solution at pH 9.0–9.5 prior to staining with Giemsa. The G-banding in prophase and prometaphase chromosomes was of better quality and more consistent than that in metaphase chromosomes.Key words:Vicia hajastana, cell line, G-banding.

ISSN:0831-2796    

DOI:10.1139/g88-009

出版商:NRC Research Press    

年代:1988

数据来源: NRC

摘要:

The amount of DNA varies widely in 20 shrubbyOxalisspecies analyzed, ranging from 1.76 pg inO.alstoniito 33.00 pg inO.dispar. This wide variation in DNA content coincided with a wide variation in chromosome size and shape. Numerical taxonomy methods showed that this variation in chromosome size and shape in shrubbyOxalisis mainly due to extra DNA. It was also possible to arrange the 20 species examined in six different groups on the basis of karyotypic similarities.Key words:Oxalis, DNA content, chromosome evolution, multivariate analysis.

ISSN:0831-2796    

DOI:10.1139/g88-010

出版商:NRC Research Press    

年代:1988

数据来源: NRC