摘要:

The impact of insecticide resistance is well documented. It includes the toxic effects of pesticides on the environment and the cost of the increased amounts of insecticides required to effectively control resistant insects. Resistance evolves by the selection of genes that confer tolerance to insecticides. Several resistance genes have been identified and cloned inDrosophila, including genes for mutant target molecules and genes that increase insecticide degradation.Drosophilais a useful system to understand the evolution of quantitative traits in general as well as the population genetics of insecticide resistance. Through it, we may hope to understand the relationship between discrete genetic change and continuously varying characters. In addition, molecular genetic techniques developed usingDrosophilacan eventually be transferred to other insects in order to help control pest populations.Key words: insecticide resistance, evolution of tolerance, selection of resistant genes, molecular genetics,Drosophila.

ISSN:0831-2796    

DOI:10.1139/g93-001

出版商:NRC Research Press    

年代:1993

数据来源: NRC

摘要:

Cytological mechanisms of 2npollen formation were investigated in microsporogenesis and sporad development in 2x, 4x, and 6xtaxa of tuber-bearingSolanumspecies that were originally collected from Mexico, and Central and South America. Parallel spindles and tripoles were seen at anaphase II in the majority of genotypes observed. The occurrence of parallel spindles and tripoles were well correlated with the occurrence of dyads and triads at the sporad stage. Further, the frequency of 2npollen predicted by frequencies of parallel spindles and tripoles and by frequencies of dyads and triads were also well correlated with observed 2npollen frequencies. Premature cytokinesis at telophase I to prophase II was seen only in 2xand 4xspecies from seriesConicibaccata. The frequency of premature cytokinesis corresponded well with the frequency of dyads leading to 2npollen formation. It was concluded that the major mechanisms of 2npollen formation in tuber-bearingSolanumspecies is parallel spindles.Key words: cytological mechanisms, parallel spindles, ploidy series, tuber-bearingSolanumspecies, 2npollen.

ISSN:0831-2796    

DOI:10.1139/g93-002

出版商:NRC Research Press    

年代:1993

数据来源: NRC

摘要:

Several polyploid species in the genusTriticumcontain a U genome derived from the diploidT.umbellulatum. In these species, the U genome is considered to be unmodified from the diploid based on chromosome pairing analysis, and it is referred to as pivotal. The additional genome(s) are considered to be modified, and they are thus referred to as differential genomes. The M genome derived from the diploidT.comosumis found in many U genome polyploids. In this study, we cloned three repetitive DNA sequences found primarily in the U genome and two repetitive DNA sequences found primarily in the M genome. We used these to monitor variation for these sequences in a large set of species containing U and M genomes. Investigation of sympatric and allopatric accessions of polyploid species did not show repetitive DNA similarities among sympatric species. This result does not support the idea that the polyploid species are continually exchanging genetic information through introgression. However, it is also possible that repetitive DNA is not a suitable means of addressing the question of introgression. The U genomes of both diploid and polyploid U genome species were similar regarding hybridization patterns observed with U genome probes. Much more variation was found both among diploidT.comosumaccessions and polyploids containing M genomes. The observed variation supports the cytogenetic evidence that the M genome is more variable than the U genome. It also raises the possibility that the differential nature of the M genome may be due to variation within the diploidT.comosum, as well as among polyploid M genome species and accessions.Key words: wheat, molecular, evolution, introgression.

ISSN:0831-2796    

DOI:10.1139/g93-003

出版商:NRC Research Press    

年代:1993

数据来源: NRC

摘要:

Cytogenetic work has shown that the tetraploid wheats,Triticum turgidumandT.timopheevii, and the hexaploid wheatT.aestivumhave one pair of A genomes, whereas hexaploidT.zhukovskyihas two. Variation in 16 repeated nucleotide sequences was used to identify sources of the A genomes. The A genomes ofT.turgidum,T.timopheevii, andT.aestivumwere shown to be contributed byT.urartu. Little divergence in the repeated nucleotide sequences was detected in the A genomes of these species from the genome ofT.urartu. InT.zhukovskyione A genome was contributed byT.urartuand the other was contributed byT.monococcum. It is concluded thatT.zhukovskyioriginated from hybridization ofT.timopheeviiwithT.monococcum. The repeated nucleotide sequence profiles in the A genomes ofT.zhukovskyishowed reduced correspondence with those in the genomes of both ancestral species,T.urartuandT.monococcum. This differentiation is attributed to heterogenetic chromosome pairing and segregation among chromosomes of the two A genomes inT.zhukovskyi.Key words: phylogeny,Triticum,Aegilops, repeated nucleotide sequences.

ISSN:0831-2796    

DOI:10.1139/g93-004

出版商:NRC Research Press    

年代:1993

数据来源: NRC

摘要:

The DNA sequencing and preliminary functional analysis of a 32 kb section of yeast chromosome I has been completed. This region lies on the left arm of the chromosome between theLTE1andSPO7genes and contains 14 open reading frames (ORFs) positioned closely together, with an average spacing of approximately 350 nucleotides between coding regions. Three of these ORFs correspond to previously identified genes, a further three show significant homology with other proteins, while the remaining eight ORFs share no significant homology to genes in the databases.Key words: chromosome I, genome analysis,Saccharomyces cerevisiae, yeast.

ISSN:0831-2796    

DOI:10.1139/g93-005

出版商:NRC Research Press    

年代:1993

数据来源: NRC

摘要:

Genetic variation in the five taxonomic groups of theStylosanthes guianensis(Aubl.) Sw. complex was investigated using random amplified polymorphic DNA markers (RAPDs). DNA samples from four plants of each of 45 accessions within theS.guianensisspecies complex were analyzed using 20 oligonucleotides of random sequence. Little variation was found within each of the 18 accessions (1–7% of total RAPD bands in pairwise comparisons) and none within each of the other 27 accessions. However, higher levels of polymorphisms were observed both within (index of genetic distance = 1 − F = 0.16–0.248) and between (1 − F = 0.254–0.408) the five taxa. This level of differentiation at the DNA level supported an earlier classification of the taxa as distinct species. A phenogram based on band sharing was constructed to show genetic relationships among the taxa studied. This phenogram corroborated the description of relationships based on morphological–agronomic characteristics, seed protein patterns, rhizobial affinities, crossability, and pollen stainability of the hybrids. In this phenogram, the most similar species wereS.grandifloraandS.hippocampoides(1 − F = 0.264), withS.acuminataalso showing closest similarity to these two species (1 − F = 0.277 and 0.283, respectively).Stylosanthes gracilisaccessions showed the closest similarity (1 − F = 0.296) toS.guianensisssp.guianensisaccessions. Lowest similarity values (1 − F = 0.335–0.411) were found between these two species andS.grandiflora,S.acuminata, andS.hippocampoides.Key words: polymerase chain reaction, random amplified polymorphic DNA,Stylosanthes guianensisspecies complex.

ISSN:0831-2796    

DOI:10.1139/g93-006

出版商:NRC Research Press    

年代:1993

数据来源: NRC

摘要:

The inheritance of random amplified polymorphic DNA (RAPD) markers generated via the polymerase chain reaction amplification of genomic DNA sequences in an F2family of an interspecific cross betweenStylosanthes hamataandS.scabrawas investigated. An initial comparison between the parental species,S.hamatacv. Verano andS.scabracv. Fitzroy, demonstrated that 34% of detected RAPD bands were polymorphic. Of 90 primers tested, 35 showed relatively simple and reliably scorable polymorphisms and were used for segregation analysis. Sixty F2individuals were scored for the segregation of 73 RAPD markers and 55 of these markers fit a 3:1 ratio. Segregation of eight other RAPD markers deviated significantly from a 3:1 ratio. There was no bias in the inheritance of RAPD markers regarding parental origin of the segregating RAPD markers. Linkage analysis revealed 10 linkage groups containing a total of 44 RAPD loci. Another 10 RAPD markers (7 of maternal origin) that were polymorphic between the parents did not segregate in the F2population. One of the maternally inherited RAPD bands hybridized to chloroplast DNA. Analysis of RAPD loci by DNA hybridization indicated that mainly repeated sequences were amplified. These data indicate that RAPDs are useful genetic markers inStylosanthesspp. and they may be suitable for genetic mapping.Key words: genetic mapping, molecular markers, polymerase chain reaction,Stylosanthes hamata,Stylosanthes scabra.

ISSN:0831-2796    

DOI:10.1139/g93-007

出版商:NRC Research Press    

年代:1993

数据来源: NRC

摘要:

The region arounddpy-14on chromosome 1 ofCaenorhabditis eleganshas been extensively studied genetically, with regard to essential gene organization. This region was one of the first for which cloned DNA was available as a result of restriction fragment length polymorphism mapping. To examine the information content of the cloned DNA in this region, evolutionarily conserved sequences were identified by cross-species hybridization. Ten regions of conservation have been identified and characterized with regard to mRNA abundance and DNA sequence. cDNAs were obtained for seven of these conserved regions and sequence from the cDNAs were used to search the SWISS protein and EMBL nucleotide data banks. Two coding regions shared DNA identities with existing sequences, the opa repeat family ofDrosophilaand theS-adenosylhomocysteine hydrolase gene. Of the three for which no corresponding cDNA were found, one corresponds to the snRNA U1-1. The other two did not detect transcripts on Northern analysis and are either conserved, but not coding, or code for low abundance transcripts. The density of conserved coding regions in this study was one per 15 kbp of genomic DNA, three times lower than that reported on chromosome 3 by the genome sequencing project.Key words:Caenorhabditis elegans, coding regions, genome, S-adenosylhomocysteine.

ISSN:0831-2796    

DOI:10.1139/g93-008

出版商:NRC Research Press    

年代:1993

数据来源: NRC

摘要:

Quantitative trait loci (QTL) controlling traits associated with winterhardiness in barley (field survival, LT50, growth habit, and crown fructan content) were mapped to chromosome 7 in a population of 100 F1-derived doubled haploid lines. The largest QTL effects for all traits were detected in a 21% recombination interval on the long arm of chromosome 7. QTL in this region accounted for 37–68% of the variation for three measures of cold tolerance, 47% of the variation for growth habit, and 28% of the variation in crown fructan content. Trait association may be due to linkage rather than pleiotropy.Key words:Hordeum vulgare, genome mapping, quantitative trait loci, winterhardiness, cold tolerance, fructan, growth habit.

ISSN:0831-2796    

DOI:10.1139/g93-009

出版商:NRC Research Press    

年代:1993

数据来源: NRC

摘要:

This paper describes the cytogenetics of the South American grassElymus magellanicus(2n = 4x = 28) and its inter- and intra-generic hybrids with North AmericanPseudoroegneria spicata(2n = 2x = 14; SS), IranianHordeum violaceum(2n = 2x = 14; HH), and North AmericanE.trachycaulus(2n = 4x = 28; SSHH),E.lanceolatus(2n = 4x = 28; SSHH), andE.glaucus(2n = 4x = 28; SSHH). Chromosome pairing in the F1hybrid ofE.magellanicus×P.spicata(2n = 3x = 21) averaged 4.09 bivalents per cell. Bivalent frequencies in theE.magellanicus×H.violaceum(2n = 3x = 21) averaged 4.86 bivalents per cell. Bivalent formation (frequencies) in hybrids between North and South American tetraploids averaged 11.42 inE.magellanicus×E.trachycaulus, 13.02 inE.magellanicus×E.lanceolatus, and 10.91 inE.magellanicus×E.glaucus. Meiotic data demonstrated thatE.magellanicusis an allotetraploid having the same basic genomes (SSHH) as North AmericanE.trachycaulus,E.lanceolatus, andE.glaucus.Key words: chromosome pairing, meiosis.

ISSN:0831-2796    

DOI:10.1139/g93-010

出版商:NRC Research Press    

年代:1993

数据来源: NRC