摘要:

Sequence-characterized amplified regions (SCARs) were developed, based on nucleotide differences within resistance gene-like fragments isolated from a potato plant carrying theRyadggene, which confers extreme resistance to potato Y potyvirus (PVY). It originates fromSolanum tuberosumsubsp. andigena, and a susceptible potato plant. SCARs were tested using 103 potato breeding lines and cultivars with diverse genetic backgrounds derived from Europe, North America, and Japan. Two markers showed high accuracy for detection of theRyadggene. The SCAR marker RYSC3 was generated only in genotypes carryingRyadg. The SCAR marker RYSC4 was detected in all genotypes carryingRyadgbut also in four PVY-susceptible genotypes. Neither marker was detected in genotypes carrying otherRygenes originating from different species thanS. tuberosumsubsp. andigena. Therefore, these SCAR markers should be powerful tools in marker-assisted selection forRyadgin potato breeding programs, and should also be useful for cloning of theRyadggene.Key words: SCAR, potato virus Y, extreme resistance gene,Solanum.

ISSN:0831-2796    

DOI:10.1139/g99-092

出版商:NRC Research Press    

年代:2000

数据来源: NRC

摘要:

In this paper, we propose a consensus sequence for a putative completeTirantretrotransposon. Several defective copies, as well as relevant sequences available in databases have been analyzed. The putative completeTirantelement is 8533 bp long, and presents all the structural features of a retroviruslike transposable element of thegypsyfamily. It contains three ORFs (open reading frames) that encode putative products resembling the retroviral Gag, Pol, and Env proteins. Southern blot analyses show that complete and defectiveTirantelements are widespread inDrosophila melanogaster.The different hybridization patterns observed in several natural populations of this species suggest thatTirantis an active element.Key words:Drosophila, LTR-retrotransposon,gypsy, retrovirus, envelope protein, phylogeny.

ISSN:0831-2796    

DOI:10.1139/g99-082

出版商:NRC Research Press    

年代:2000

数据来源: NRC

摘要:

We have used eight pairs of simple sequence repeat (SSR) primers to analyse the genetic diversity in 130 individuals of coconut (Cocos nuciferaL.) comprising 75 tall individuals and 55 dwarf individuals, representing 94 different coconut ecotypes throughout the world. A total of 51 alleles were detected, with an average of 6.4 alleles per locus. Fifty alleles were detected in tall coconuts (talls; mean alleles/locus 6.3) compared with only 26 (mean/ locus 3.3) in dwarfs, and the average diversity value in talls (0.589) was also significantly higher than that in dwarfs (0.348). Using the eight SSRs we were able to uniquely discriminate 116 of the 130 individuals. A phenetic tree based onDAD(absolute distance) values clustered individuals into five groups, each mainly composed of either talls or dwarfs. These results provide evidence in support of previous hypotheses concerning the dissemination of coconut, as well as important new information for conservation and breeding purposes.Key words: coconut,Cocos nucifera, microsatellites, SSR, genetic diversity.

ISSN:0831-2796    

DOI:10.1139/g99-079

出版商:NRC Research Press    

年代:2000

数据来源: NRC

摘要:

Fluorescence in situ hybridization (FISH) with a PCR-amplified 18S ribosomal probe was used to map rDNA loci in 19 taxa of the ground beetle genusZabrus(2n= 47-63) from the Iberian Peninsula. A quantitative and qualitative variation has been observed among related species, subspecies, populations, and even individuals. The number of rDNA-carrying chromosomes varies from 2 to 12, and the extent of the signal from small dots to entire arms. Changes altering the number of rDNA clusters seem to be uncoupled from the variation found in the chromosome number. Mechanisms that explain the numerical variation and spreading of rDNA clusters throughout the genome within the genusZabrusare briefly discussed. No concordance between the pattern of rDNA sites and the phylogenetic relationships as based on morphological characters has been found.Key words: Carabidae, Coleoptera, fluorescence in situ hybridization, polymorphism, ribosomal DNA,Zabrus.

ISSN:0831-2796    

DOI:10.1139/g99-097

出版商:NRC Research Press    

年代:2000

数据来源: NRC

摘要:

We have constructed a tomato genetic linkage map based on an intraspecific cross between two inbred lines ofLycopersicon esculentumandL. esculentumvar.cerasiforme. The segregating population was composed of 153 recombinant inbred lines. This map is comprised of one morphological, 132 RFLP (restriction fragment length polymorphism, including 16 known-function genes), 33 RAPD (random amplified polymorphic DNA), and 211 AFLP (amplified fragment length polymorphism) loci. We compared the 3 types of markers for their polymorphism, segregation, and distribution over the genome. RFLP, RAPD, and AFLP methods revealed 8.7%, 15.8%, and 14.5% informative bands, respectively. This corresponded to polymorphism in 30% of RFLP probes, 32% of RAPD primers, and 100% of AFLP primer combinations. Less deviation from the 1:1 expected ratio was obtained with RFLP than with AFLP loci (8% and 18%, respectively). RAPD and AFLP markers were not randomly distributed over the genome. Most of them (60% and 80%, respectively) were grouped in clusters located around putative centromeric regions. This intraspecific map spans 965 cM with an average distance of 8.3 cM between markers (of the framework map). It was compared to other published interspecific maps of tomato. Despite the intraspecific origin of this map, it did not show any increase in length when compared to the high-density interspecific map of tomato.Key words:Lycopersicon esculentum, molecular linkage map, RFLP, AFLP, intraspecific cross.

ISSN:0831-2796    

DOI:10.1139/g99-096

出版商:NRC Research Press    

年代:2000

数据来源: NRC

摘要:

A Norway spruce (Picea abiesK.) cDNA library obtained from vegetative bud tissue was screened for the presence of (AG)nand (AC)nmicrosatellite repeats. Ten (AG)nand six (AC)nmicrosatellites were found, with an average length of 25.5 repeat units. Most of the microsatellites are simple perfect repeats. The microsatellite distribution within the clones is clearly non-random, with different classes of repeats lying in different positions relative to the coding region and in a highly conserved orientation. An estimate of the frequency of dinucleotide microsatellites in expressed regions was obtained, showing that SSRs (simple sequence repeats) are found in genes about 20 times less frequently than in random genomic clones, with (AG)nrepeats more frequent than (AC)nrepeats. Potential applications of these sequences as expressed region-based molecular markers are shown by developing six SSR markers for the detection of natural variation in Norway spruce populations and testing two of them for the identification of illegitimate progenies from a mapping population.Key words:Picea abies, microsatellites, SSRs, ESTs, population genetics, trees.

ISSN:0831-2796    

DOI:10.1139/g99-095

出版商:NRC Research Press    

年代:2000

数据来源: NRC

摘要:

The polymerase chain reaction (PCR) has become a standard procedure in plant genetics, and is the basis for many emerging genomics approaches to mapping and gene identification. One advantage of PCR is that sequence information for primer sets can be exchanged between laboratories, obviating the need for exchange and maintenance of biological materials. Repeatability of primer sets, whereby the same products are amplified in different laboratories using the same primer set, is important to successful exchange and utilization. We have developed several hundred sequence-tagged site (STS) primer sets for wheat and barley. The ability of the primer sets to generate reproducible amplifications in other laboratories has been variable. We wished to empirically determine the properties of the primer sets that most influenced repeatability. A total of 96 primer sets were tested with four genomic DNA samples on each of four thermocyclers. All major bands were repeatable across all four thermocyclers for approximately 50% of the primer sets. Characteristics most often associated with differences in repeatability included primer GC content and 3'-end stability of the primers. The propensity for primer-dimer formation was not a factor in repeatability. Our results provide empirical direction for the development of repeatable primer sets.Key words: STS-PCR primers, wheat, barley.

ISSN:0831-2796    

DOI:10.1139/g99-087

出版商:NRC Research Press    

年代:2000

数据来源: NRC

摘要:

Drought is the major abiotic stress limiting rice (Oryza sativa) production and yield stability in rainfed lowland and upland ecosystems. Root systems play an important role in drought resistance. Incorporation of root selection criteria in drought resistance improvement is difficult due to lack of reliable and efficient screening techniques. Using a wax-petrolatum layer system simulated to compacted soil layers, root traits were evaluated in a doubled haploid (DH) population derived from the cross between 'IR64' and 'Azucena'. Twelve putative QTLs (quantitative trait loci) were detected by interval mapping comprising four QTLs for root-penetration ability, four QTLs for root thickness, two QTLs for penetrated root number, and two QTLs for total root number. These QTLs individually explained 8.4% to 16.4% of the phenotypic variation. No QTL was detected for maximum penetrated root length by interval mapping. One QTL located between RG104 and RG348 was found to influence both root-penetration ability and root thickness. QTLs for root-penetration ability and root thickness were compared across two populations, 'IR64'-'Azucena' and 'CO39'-'Moroberekan', and different testing conditions. The identified consistent QTLs could be used for marker-assisted selection for deep and thick roots with high root-penetration ability in rice.Key words: quantitative trait loci, root-penetration ability, root thickness, rice, drought.

ISSN:0831-2796    

DOI:10.1139/g99-065

出版商:NRC Research Press    

年代:2000

数据来源: NRC

摘要:

We applied the cDNA-AFLP (amplified fragment length polymorphism) technique to mRNA from the parents of a cassava (Manihot esculenta) genetic mapping population, and obtained more than 500 transcript-derived fragments (TDFs) that were unique in either parent. A subset of 50 TDFs were cloned and sequenced. Sequence alignment of the expressed sequence tags (ESTs) revealed mostly genes of unknown function. Six of the TDFs were mapped on to the cassava genetic map. We also demonstrated by genetic mapping of the TDFs, as RFLP (restriction fragment length polymorphism) markers, that TDFs are more polymorphic than random cDNAs. Generation of ESTs as differentially expressed sequences, in time or between different varieties, is proposed as a way of developing ESTs around specific traits for the candidate locus approach to mapping complex traits.Key words: cassava, genetic mapping, cDNA-AFLP technique, ESTs (expressed sequence tags).

ISSN:0831-2796    

DOI:10.1139/g99-073

出版商:NRC Research Press    

年代:2000

数据来源: NRC

摘要:

Three chloroplast microsatellites (cpSSRs), previously sequence characterized and for which paternal inheritance was tested and confirmed, were used to assess their usefulness as informative markers for phylogeographic studies in Norway spruce (Picea abiesK.) and to detect spatial genetic differentiation related to the possible recolonization processes in the postglacial period. Ninety-seven populations were included in the survey. Some 8, 7, and 6 different size variants for the three cpSSRs, respectively, were scored by analysing 1105 individuals. The above 21 variants combined into 41 different haplotypes. The distribution of some haplotypes showed a clear geographic structure and seems to be related to the existence of different refugia during the last glacial period. The analysis of chloroplast SSR variation detected the presence of two main gene pools (Sarmathic-Baltic and Alpine - Centre European) and a relatively low degree of differentiation (RSTof about 10%), characteristic of tree species with large distribution and probably influenced by an intensive human impact on this species. Based on our data, we were not able to detect any evidence concerning the existence of additional gene pools (e.g., from Balkan and Carpathian glacial refugia), though we cannot exclude the existence of genetic discontinuity within the species' European range. A large proportion of population-specific haplotypes were scored in this species, thus indicating a possible usefulness of these markers for the identification of provenances, seed-lots, and autochthonous stands.Key words: haplotypic diversity, phylogeography, chloroplast microsatellites, recolonization.

ISSN:0831-2796    

DOI:10.1139/g99-093

出版商:NRC Research Press    

年代:2000

数据来源: NRC