摘要:

The house mouse is one of the model organisms in genetics and more than 400 inbred strains have been established. However, many of the strains are related and their ancestry can be traced back to European fancy mice inbred in the 1920s. Recent molecular studies corroborate the early historical records that assert that Japanese fancy mice were introduced into European stocks and thus contributed to the development of "old" inbred strains. Consequently, many inbred strains have genomic DNA derived from more than one subspecies ofMus musculus. The subspecific hybrid origin of common inbred strains has important bearings on the interpretation of genetic data, and the limitations that history imposes upon the currently available strains make it necessary to establish new inbred strains representing specific wild populations.

ISSN:0831-2796    

DOI:10.1139/g95-001

出版商:NRC Research Press    

年代:1995

数据来源: NRC

摘要:

In order to counteract the effects of the mutant genes in races of leaf rust (Puccinia reconditaf.sp.triticiRob. ex Desm.) and stem rust (P.graminisf.sp.triticiEriks. &Henn.) in wheat, exploration of new resistance genes in wheat relatives is necessary. Three accessions ofTriticum cylindricumCes. (4x, CCDD), Acy1, Acy9, and Acy11, were tested with 10 races each of leaf rust and stem rust. They were resistant to all races tested. Viable F1plants were produced from the crosses of theT.cylindricumaccessions as males with susceptible MP and Chinese Springph1bhexaploid wheats (T.aestivum, 6x, AABBDD), but not with susceptible Kubanka durum wheat (T.turgidumvar.durum, 4x, AABB), even with embryo rescue. In these crosses the D genome of hexaploid wheat may play a critical role in eliminating the barriers for species isolation during hybrid seed development. TheT.cylindricumrust resistance was expressed in the F1hybrids with hexaploid wheat. However, only the cross MP/Acy1 was successfully backcrossed to another susceptible hexaploid wheat, LMPG-6. In the BC2F2of the cross MP/Acy1//LMPG-6/3/MP, monosomic or disomic addition lines with resistance to either leaf rust race 15 (infection types (IT) 1=, 1, or 1+; addition line 1) or stem rust race 15B-1 (IT 1 or 1+; addition line 2) were selected. Rust tests and examination of chromosome pairing of the F1hybrids and the progeny of the disomic addition lines confirmed that the genes for rust resistance were located on the addedT.cylindricumC-genome chromosomes rather than on the D-genome chromosomes. TheT.cylindricumchromosome in addition line 2 was determined to be chromosome 4C through the detection of RFLPs among the genomes using a set of homoeologous group-specific wheat cDNA probes. Addition line 1 was resistant to the 10 races of leaf rust and addition line 2 was resistant to the 10 races of stem rust, as was theT.cylindricumparent. The added C-genome chromosomes occasionally paired with hexaploid wheat chromosomes. Translocation lines with rust resistance (2n = 21 II) may be obtained in the self-pollinated progeny of the addition lines through spontaneous recombination of the C-genome chromosomes and wheat chromosomes. Such translocation lines with resistance against a wide spectrum of rust races should be potentially valuable in breeding wheat for rust resistance.Key words: wheat,Triticum cylindricum, rust resistance, gene transfer, addition line, molecular cytogenetics.

ISSN:0831-2796    

DOI:10.1139/g95-002

出版商:NRC Research Press    

年代:1995

数据来源: NRC

摘要:

Meiosis was studied in 11 primary trisomics (2n = 2x + 1 = 25) from diploidSolanum tuberosumL. ssp.tuberosumHawkes (2n = 2x = 24) and from interspecificSolanumhybrids. The three homologous chromosomes were associated in a trivalent in 90% of more than 175 pollen mother cells analysed at pachytene. Trivalents showing a two by two pairing and partner exchanges at pachytene along with incomplete triple synapsis were frequently observed. Foldback pairing, predominantly observed in the heterochromatic parts of the chromosomes, occurred in 28.3% of the trivalents. Nonhomologous association of chromosome segments was observed in 29.1% of the trivalents. Up to six telomeres were associated homologously in 46.2% of the trivalents. Genotypic differences with respect to trivalent formation at metaphase I occurred in almost all the trisomic types and was significant for the trisomics for chromosomes 4, 7, and 9. The coefficient of realization of a trivalent (CRT) at metaphase I in the 11 primary trisomics varied from 0.20 to 0.80, and was positively correlated with the absolute length of the extra chromosome (r = 0.61,p ≤ 0.05) and with the absolute, as well as the relative, length of the euchromatic segments of the extra chromosome (r = 0.70,p ≤ 0.05). There was no apparent relationship between the CRT and the distribution pattern at anaphase I or anaphase II. The rate of female transmission of the extra chromosome varied from 10.0 to 44.6% among different trisomics. For chromosomes 4, 7, and 9, this rate differed significantly among genotypes of the same trisomic.Key words: primary trisomics, meiosis, nonhomologous chromosome association, telomere pairing, triple synapsis, female transmission,Solanum.

ISSN:0831-2796    

DOI:10.1139/g95-003

出版商:NRC Research Press    

年代:1995

数据来源: NRC

摘要:

The first direct sexual hybrids between diploid nontuber-bearing species and diploid potato breeding lines are reported here. Three nontuberous species ofSolanum,S.brevidens,S.etuberosum, andS.fernandezianum, were used for sexual crosses, achieved by a combination of rescue pollinations and embryo rescue. Initial hybrid selection was made using an embryo spot marker, followed by the evaluation of morphological and reproductive traits. Putative hybrids were first tested for resistance to potato leaf roll virus derived from the wild species, and then were tested with molecular markers using species-specific DNA probes. Finally, the tuberization of several 2xhybrids was tested for actual potato germplasm enhancement. These hybrids are unique in terms of their potential to enhance recombination between chromosomes of wild species and those of cultivated potatoes in germplasm utilization, and to exploit the genetic nature of tuber formation. The finding that nontuber-bearingSolanumspp. can be directly crossed with tuber-bearing species also has important implications for the regulatory aspects of the use of genetically modified organisms.Key words: nontuber-bearingSolanum, potato germplasm enhancement, interspecific crosses, chromosome manipulation, inter-EBN crosses, diploid.

ISSN:0831-2796    

DOI:10.1139/g95-004

出版商:NRC Research Press    

年代:1995

数据来源: NRC

摘要:

A F2population of two celery cultivated types (Apium graveolensL. var.rapaceumandA.graveolensL. var.secalinum) was used to construct a linkage map consisting of 29 RFLP (restriction fragment length polymorphism), 100 RAPD (random amplified polymorphic DNA), four isozyme, one disease resistance, and one growth habit markers. The map contains 11 major groups and 9 small groups and has a total length of 803 cM with an average distance of 6.4 cM between two adjacent loci. Ten percent of the RAPDs segregated as codominant markers and their allelic homologies were tested by Southern hybridization. One-quarter of the dominant RAPDs were linked in repulsion phase, whereas the majority of them were linked to either codominant or dominant markers in coupling phase. About 10% of the markers showed significant segregation distortion. The detectable level of duplications in the celery genome was relatively low.Key words:Apium graveolens, RFLP, RAPD, linkage map.

ISSN:0831-2796    

DOI:10.1139/g95-005

出版商:NRC Research Press    

年代:1995

数据来源: NRC

摘要:

Group 1 chromosomes of the Triticeae tribe have been studied extensively because many important genes have been assigned to them. In this paper, chromosome 1 linkage maps ofTriticum aestivum,T.tauschii, andT.monococcumare compared with existing barley and rye maps to develop a consensus map for Triticeae species and thus facilitate the mapping of agronomic genes in this tribe. The consensus map that was developed consists of 14 agronomically important genes, 17 DNA markers that were derived from known-function clones, and 76 DNA markers derived from anonymous clones. There are 12 inconsistencies in the order of markers among seven wheat, four barley, and two rye maps. A comparison of the Triticeae group 1 chromosome consensus map with linkage maps of homoeologous chromosomes in rice indicates that the linkage maps for the long arm and the proximal portion of the short arm of group 1 chromosomes are conserved among these species. Similarly, gene order is conserved between Triticeae chromosome 1 and its homoeologous chromosome in oat. The location of the centromere in rice and oat chromosomes is estimated from its position in homoeologous group 1 chromosomes of Triticeae.Key words: Triticeae, RFLP, consensus, comparative.

ISSN:0831-2796    

DOI:10.1139/g95-006

出版商:NRC Research Press    

年代:1995

数据来源: NRC

摘要:

The ability ofSolanum tuberosumGroup Andigena clones to produce triploids (2n = 3x = 36) in 4x(4 endosperm balance number (EBN)) × 2x(2EBN) crosses was investigated. The difference in triploid production among the clones tested, though large, appears to be the result of low heritability. The triploids produced in the 4x × 2xcrosses did not seem to bear heritable factors that improved triploid production in 2xand 4xpopulations derived from them. Yet, the seeds/fruit data from a similar 4x × 2xcross fit a Poisson distribution. It was argued that the low probability nonheritable random events responsible for the triploids from 4x × 2xand 2x × 4xcrosses were misfertilizations, mitotic abnormalities in the gametophyte, and (or) mitotic misdivisions in the endosperm.Key words:Solanum, endosperm, triploid block, fertilization.

ISSN:0831-2796    

DOI:10.1139/g95-007

出版商:NRC Research Press    

年代:1995

数据来源: NRC

摘要:

Nucleolus organizer region (NOR) activity was analysed in four types of males of the grasshopperEyprepocnemis plorans, possessing two kinds of supernumerary heterochromatin: a B chromosome and a supernumerary chromosome segment proximally located on the smallest autosome (S11). In males lacking extra heterochromatin, the four active NORs located on the S9, S10, S11, and X chromosomes showed independent activity patterns, but several kinds of dependence appeared in the presence of supernumerary heterochromatin. Furthermore, temporal changes in NOR activity were observed during the first 2 weeks of adult life in standard males but not in males carrying supernumerary heterochromatin. It is suggested that all these effects are related to the DNA content of both types of extra heterochromatin.Key words: NOR, supernumerary heterochromatin, grasshopper,Eyprepocnemis plorans.

ISSN:0831-2796    

DOI:10.1139/g95-008

出版商:NRC Research Press    

年代:1995

数据来源: NRC

摘要:

Near-isolines carrying four different genes for resistance to leaf rust were used to find linked molecular markers for these genes. Clones used to detect polymorphism were selected on the basis of the reported chromosomal location of the resistance genes. BothLophopyron-derived resistance genes,Lr19andLr24, cosegregated with eight molecular markers assigned to chromosomes 7DL and 3DL, respectively. One clone cosegregated withLr9and two closely linked RFLP markers were found forLr32, mapping at 3.3 ± 2.6 and 6.9 ± 3.6 cM from the resistance gene. TheLophopyron-chromatin segment in isolines carrying chromosomes 7E (Lr19) and 3E (Lr24) replaced a large portion of chromosome 7D and the distal portion of chromosome 3D, respectively. Clones assigned to these chromosomes on the basis of aneuploid analysis hybridized to 7E and 3E segments, thus confirming cytological results that these introgressed segments represent homoeologous chromosomes. The linked RFLP markers could be used to identify the resistance genes and generate new combinations in breeding populations, especially in the absence of disease in the environment or when virulence is lacking.Key words: leaf rust, RFLP,Lophopyron, gene tagging, wheat,Aegilops umbellulata,Triticum tauschii.

ISSN:0831-2796    

DOI:10.1139/g95-009

出版商:NRC Research Press    

年代:1995

数据来源: NRC

摘要:

This paper describes the distribution of highly polymorphic GATA- and GACA-containing DNA regions in tomato. To study the distribution of these polymorphic regions, a mapping experiment was done. The segregation of 32 GATA- and GACA-containing loci was analyzed in a F2population from a cross betweenLycopersicon esculentumandL.pennellii. From these loci, 28 could be mapped to 8 of the 12 tomato chromosomes. Both the GATA- and GACA-containing loci seem to cluster in the same chromosomal regions. To our knowledge, this is the first report on mapping of GATA- and GACA-containing loci in plants.Key words: mapping, microsatellites,Lycopersicon esculentum, RFLP, DNA-fingerprinting.

ISSN:0831-2796    

DOI:10.1139/g95-010

出版商:NRC Research Press    

年代:1995

数据来源: NRC