共查询到20条相似文献,搜索用时 31 毫秒
1.
The barley Rar1 gene is an essential component of the race-specific, Mla-12-specified powdery mildew resistance reaction. As part of a map-based cloning strategy designed to isolate Rar1, five barley yeast artificial chromosomes (YACs) have been identified, ranging in size from 300 to 1100?kb. PCR-based YAC end-specific markers have been established and were employed to construct a local YAC contig. Four out of five YAC clones were found to be non-colinear with the source DNA. High-resolution genetic mapping of the YAC ends demonstrated that the set of five overlapping YAC clones encompasses the barley Rar1 gene. 相似文献
2.
T. Lahaye S. Hartmann S. Töpsch A. Freialdenhoven M. Yano P. Schulze-Lefert 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1998,97(4):526-534
The Mla-12-mediated resistance in barley against Erysiphe graminis f. sp. hordei requires for its function the Rar1 gene. High-resolution genetic mapping was accomplished by inspecting more than 4000 plants segregating for Rar1 within an 0.7-cM interval containing the target gene. Marker enrichment in the target region was carried out by an amplified
fragment length polymorphism (AFLP)-based search for polymorphic loci using bulked DNA templates from resistant and susceptible
recombinants adjacent to Rar1. RFLP markers closely linked to Rar1 were used to investigate the relationship between physical and genetical distances by PFGE Southern analysis, indicating
the physical linkage of two genetically separated RFLP loci. Comparative mapping of Rar1-linked RFLP probes in barley and rice identified a break of collinearity in the orthologous chromosome segments.
Received: 11 February 1998 / Accepted: 3 March 1998 相似文献
3.
Two yeast artificial chromosomes (YACs) containing genomic DNA from tomato have been isolated using CT220, an RFLP marker
which is tightly linked to the tomato spotted wilt virus resistance gene, Sw-5. High-resolution mapping of the YAC ends and internal YAC probes demonstrated that one of the YAC clones, TY257 (400 kb),
spans Sw-5. By chromosome walking in a cosmid library, the position of Sw-5 has been delimited within the YAC to a maximal chromosomal segment of 100 kb, spanned by nine overlapping cosmid clones.
Received: 13 March 1997 / Accepted: 11 may 1997 相似文献
4.
G. Schwarz W. Michalek V. Mohler G. Wenzel A. Jahoor 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1999,98(3-4):521-530
The complex Mla locus of barley determines resistance to the powdery mildew pathogen Erysiphe graminis f. sp. hordei. With a view towards gene isolation, a population consisting of 950 F2 individuals derived from a cross between the near-isogenic lines ‘P01’ (Mla1) and ‘P10’ (Mla12) was used to construct a high-resolution map of the Mla region. A fluorescence-based AFLP technique and bulked segregant analysis were applied to screen for polymorphic, tightly
linked AFLP markers. Three AFLP markers were selected as suitable for a chromosome-landing strategy. One of these AFLP markers
and a closely linked RFLP marker were converted into sequence-specific PCR markers. PCR-based screening of approximately 70 000
yeast artificial chromosome (YAC) clones revealed three identical YACs harbouring the Mla locus. Terminal insert sequences were obtained using inverse PCR. The derived STS marker from the right YAC end-clone was
mapped distal to the Mla locus.
Received: 17 July 1998 / Accepted: 9 August 1998 相似文献
5.
D. Leister A. Berger H. Thelen W. Lehmann F. Salamini C. Gebhardt 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1997,95(5-6):954-960
A yeast artificial chromosome (YAC) library was constructed from high-molecular-weight DNA of potato (Solanum tuberosum). Potato DNA fragments obtained after complete digestion with four different rare-cutter restriction enzymes were cloned
using the pYAC-RC vector. The library consists of 21 408 YAC clones with an average insertion size of 140 kb. The frequency
of YAC clones having insertions of chloroplast or mitochondrial DNA was estimated to be 0.5% and 0.3%, respectively. The YAC
library was screened by PCR with 11 DNA markers detecting single genes or small gene families in the potato genome. YACs for
8 of the 11 markers were detected in the library. Using 2 markers that are linked to the resistance genes R1 and Gro1 of potato, we isolated two individual YAC clones. One of these YAC clones was found to harbour one member of a small family
of candidate genes for the nematode resistance gene Gro1.
Received : 5 May 1997 / Accepted : 20 May 1997 相似文献
6.
The pathogenesis-related accumulation of superoxide radical anions (O·−
2) and hydrogen peroxide (H2O2) was comparatively analyzed in a barley line (Hordeum vulgare L. cv Sultan-5) carrying the powdery mildew (Blumeria graminis f.sp. hordei, Speer, Bgh) resistance gene Mla12, and in susceptible mutants defective in Mla12 or in genes “required for Mla12-specified disease resistance” (Rar1 and Rar2). In-situ localization of reactive oxygen intermediates was performed both by microscopic detection of azide-insensitive
nitroblue tetrazolium (NBT) reduction or diaminobenzidine (DAB) polymerization, and by an NBT-DAB double-staining procedure.
The Mla12-mediated hypersensitive cell death occurred either in attacked epidermal cells or adjacent mesophyll cells of wild-type plants.
Whole-cell H2O2 accumulation was detected in dying cells, while O·−
2 emerged in adjacent cells. Importantly, all susceptible mutants lacked these reactions. An oxalate oxidase, which is known
to generate H2O2 and has been implicated in barley resistance against the powdery mildew fungus, was not differentially expressed between
the wild type and all mutants. The results demonstrate that the Rar1 and Rar2 gene products, which are control elements of R-gene-mediated programmed cell death, also control accumulation of reactive oxygen intermediates but not the pathogenesis-related
expression of oxalate oxidase.
Received: 7 January 2000 / Accepted: 2 June 2000 相似文献
7.
Isolation and FISH mapping of Yeast Artificial Chromosomes (YACs) encompassing an allele of the Gm2 gene for gall midge resistance in rice 总被引:2,自引:0,他引:2
K. R. Rajyashri S. Nair N. Ohmido K. Fukui N. Kurata T. Sasaki M. Mohan 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1998,97(4):507-514
Ten yeast artificial chromosomes (YACs) spanning the Gm2 locus have been isolated by screening high-density filters containing a total of approximately 7000 YAC (representing six
genome equivalents) clones derived from a japonica rice, Nipponbare. The screening was done with five RFLP markers flanking a gall midge resistance gene, Gm2, which was previously mapped onto chromosome 4 of rice. This gene confers resistance to biotype 1 and 2 of gall midge (Orseolia oryzae), a major insect pest of rice in South and Southeast Asia. The RFLP markers RG214, RG329 and F8 hybridized with YAC Y2165.
Two overlapping YAC clones (Y5212 and Y2165) were identified by Southern hybridization, with Gm2-flanking RFLP markers, and their inserts isolated. The purified YACs and RFLP markers flanking Gm2 were labeled and physically mapped by the fluorescence in situ hybridization (FISH) technique. All of them mapped to the long arm of chromosome 4 of the resistant variety of rice, ‘Phalguna’,
confirming the previous RFLP mapping data.
Received: 15 December 1997 / Accepted: 5 March 1998 相似文献
8.
Many blue-light mediated physiological responses have been studied in the fern Adiantum capillus-veneris. We have isolated genomic clones encoding sequences similar to those encoding blue-light photoreceptors (cryptochromes) in
higher plants using the Arabidopsis CRY1 cDNA as a probe, and these positive clones fall into five independent groups. Using RACE procedures, we obtained full-length
cDNA sequences for three of these five groups. The deduced amino acid sequences include the photolyase-homologous domain in
the N-terminal half, and they also contain a C-terminal extension of about 200 amino acids in length. These structural features
indicate that the genes indeed encode Adiantum cryptochromes and represent a small gene family having at least three members.
Received: 16 February 1998 / Accepted: 26 April 1998 相似文献
9.
RFLP- and physical mapping of resistance gene homologues in rice (O. sativa) and Barley (H. vulgare)
D. Leister J. Kurth D. A. Laurie M. Yano T. Sasaki A. Graner P. Schulze-Lefert 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1999,98(3-4):509-520
The deduced peptide sequences of 25 gene fragments of NBS-LRR resistance (R) gene homologues from rice and barley and of characterized R genes were compared, revealing a string of six conserved motifs. Mapping of the R-gene candidates in rice showed linkage to genes conferring race-specific resistance to rice blast (Pi-k, Pi-f and Pi-1) and bacterial blight disease (Xa-1, Xa-3 and Xa-4), in barley to powdery mildew (Mla) and the rust fungus (Rpg1). In rice four mixed clusters were detected, each harboring at least two highly dissimilar NBS-LRR genes. A YAC-contig was
established for one of these mixed clusters. YAC fragmentation experiments revealed the presence of at least five NBS-LRR
genes within 200 kb in head-to-tail orientation.
Received: 24 July 1998 / Accepted: 14 August 1998 相似文献
10.
Generation of a soybean BAC library, and identification of DNA sequences tightly linked to the Rps1-k disease resistance gene 总被引:5,自引:0,他引:5
S. S. Salimath M. K. Bhattacharyya 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1999,98(5):712-720
A soybean bacterial artificial chromosome (BAC) library, comprising approximately 45 000 clones, was constructed from high-molecular-weight
nuclear DNA of cultivar Williams 82, which carries the Rps1-k gene for resistance against Phytophthora sojae. The library is stored in 130 pools with about 350 clones per pool. Completeness of the library was evaluated for 21 random
sequences including four markers linked to the Rps1 locus and 16 cDNAs. We identified pools containing BACs for all sequences except for one cDNA. Additionally, when screened
for possible contaminating BAC clones carrying chloroplast genes, no sequences homologous to two barley chloroplast genes
were found. The estimated average insert size of the BAC clones was about 105 kb. The library comprises about four genome
equivalents of soybean DNA. Therefore, this gives a probability of 0.98 of finding a specific sequence from this library.
This library should be a useful resource for the positional cloning of Rps1-k, and other soybean genes. We have also evaluated the feasibility of an RFLP-based screening procedure for the isolation
of BAC clones specific for markers that are members of repetitive sequence families, and are linked to the Rps1-k gene. We show that BAC clones isolated for two genetically linked marker loci, Tgmr and TC1-2, are physically linked. Application of this method in expediting the map-based cloning of a gene, especially from
an organism, such as soybean, maize and wheat, with a complex genome is discussed.
Received: 12 May 1998/Accepted: 24 August 1998 相似文献
11.
W. Michalek M. Kleine H. Dargatz G. Wenzel A. Jahoor 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1997,95(3):369-374
The hordeins are the major class of storage proteins in barley and are encoded by multigene families. Two YAC-clones specific
for the C-hordein-coding Hor1-locus of barley (Hordeum vulgare L.) were selected. The clones were constructed with DNA from the cultivars ‘Franka’ and ‘Hockey’ and have insert sizes of
330 kb and 350 kb, respectively. Performing partial digestions and hybridizations with vector-specific probes, a restriction
analysis was conducted using restriction enzymes with a 8-bp recognition sequence. Both clones cover the complete region of
the Hor1-locus, but exhibit a different pattern of restriction sites reflecting the polymorphic nature of the locus on the scale of
long-range restriction mapping. The maximal extent of the regions homologous to the Hor1-specific probe, pBSC5, was 105 kb in the ‘Hockey’-derived YAC and 190 kb in the yeast artificial chromosome constructed with
‘Franka’-DNA. Furthermore the high degree of instability observed with the Hor1-specific YAC-clones is discussed in conjunction with the structure of the Hor1-locus.
Received: 19 December 1996 / Accepted: 31 January 1997 相似文献
12.
Genes controlling hydroxylations of phytosiderophores are located on different chromosomes in barley (Hordeum vulgare L.) 总被引:3,自引:0,他引:3
Jian Feng Ma Shin Taketa Yi-Chieh Chang Takashi Iwashita Hideaki Matsumoto Kazuyoshi Takeda Kyosuke Nomoto 《Planta》1999,207(4):590-596
Phytosiderophores, mugineic acids, have been demonstrated to be involved in Fe acquisition in gramineous plants. In this
study, chromosomal arm locations of genes encoding for biosynthesis of various phytosiderophores were identified in a cultivar
of barley (Hordeum vulgare L. cv. Betzes). Using wheat (Triticum aestivum L. cv. Chinese Spring)-barley (cv. Betzes) ditelosomic addition lines for 4HS and 4HL, a gene for hydroxylation of 2′-deoxymugineic
acid to mugineic acid was localized to the long arm of barley chromosome 4H. To locate the gene for hydroxylation of mugineic
acid to 3-epihydroxymugineic acid, hybrids between the 4H addition line and other wheat-barley addition lines were studied.
Only a hybrid between 4H and 7H addition lines produced 3-epihydroxymugineic acid. The gene was further localized to the long
arm of chromosome 7H by feeding mugineic acid to ditelosomic addition lines for 7HS and 7HL. A new phytosiderophore was discovered
in both 7H and 7HL addition lines, which was identified to be 3-epihydroxy-2′-deoxymugineic acid by detailed nuclear magnetic
resonance studies. These results revealed that in barley there are two pathways from 2′-deoxymugineic acid to 3-epihydroxymugineic
acid: 2′-deoxymugineic acid → mugineic acid → 3-epihydroxymugineic acid and 2′-deoxymugineic acid → 3-epihydroxy-2′-deoxymugineic
acid → 3-epihydroxymugineic acid. Barley genes encoding for the hydroxylations of phytosiderophores are located in different
chromosomes and each gene hydroxylates different C-positions: the long arm of chromosome 4H carries the gene for hydroxylating
the C-2′ position and the long arm of chromosome 7H carries the gene for hydroxylating the C-3 position of the azetidine ring.
Received: 10 August 1998 / Accepted: 30 September 1998 相似文献
13.
Makoto Takano Hiromi Kajiya-Kanegae Hideyuki Funatsuki Shoshi Kikuchi 《Molecular & general genetics : MGG》1998,260(4):388-394
We have isolated five cDNA clones (osk1–5) for protein kinases from rice which are related to SNF1 protein kinase of Saccharomyces cerevisiae. Based on the sequence homology, these cDNAs can be classified into two groups, group 1 (osk1) and group 2 (osk2–5). The products of these genes were demonstrated to be functional SNF1-related protein kinases by in vitro and in vivo experiments.
Recombinant proteins expressed from both groups of genes were fully active as protein kinases and could phosphorylate SAMS
peptide, a substrate specific for the SNF1/AMPK family, as well as themselves (autophosphorylation). Moreover, expression
of osk3 cDNA in yeast snf1 mutants restored SNF1 function. Northern blot analyses showed differential expression of these two gene groups; group 1 is expressed uniformly
in growing tissues (young roots, young shoots, flowers, and immature seeds), whereas group 2 is strongly expressed in immature
seeds. SNF1-related protein kinases have been reported from different plant species, such as rye, barley, Arabidopsis, tobacco, and potato, while the type of gene strongly expressed in immature seeds is known only in cereals such as rye, barley,
and, from our findings, in rice. Expression levels of the group 2 genes were further analyzed in seeds during seed maturation.
Expression is transiently increased in the early stages of seed maturation and then decreases. The expression peak precedes
those of the sbe1 and waxy genes, which are involved in starch synthesis in rice. Taken together, these findings suggest that group 2 OSK genes play important roles in the early stages of endosperm development in rice seeds.
Received: 30 April 1998 / Accepted: 20 August 1998 相似文献
14.
X.-B. Zhong J. Bodeau P. F. Fransz V. M. Williamson A. van Kammen J. H. de Jong P. Zabel 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1999,98(3-4):365-370
The root-knot nematode resistance gene Mi-1 in tomato has long been thought to be located in the pericentromeric heterochromatin region of the long arm of chromosome
6 because of its very tight genetic linkage (approx. 1 cM) to the markers Aps-1 (Acid phosphatase 1) and yv (yellow virescent). Using Mi-BAC clones and an Aps-1 YAC clone in fluorescence in situ hybridisation (FISH) to pachytene
chromosomes we now provide direct physical evidence showing that Mi-1 is located at the border of the euchromatin and heterochromatin regions in the short arm (6S) and Aps-1 in the pericentromeric heterochromatin of the long arm (6L) close to the euchromatin. Taking into account both the estimated
DNA content of hetero- and euchromatin regions and the compactness of the tomato chromosomes at pachytene (2 Mb/μm), our data
suggest that Mi-1 and Aps-1 are at least 40 Mb apart, a base pair-to-centiMorgan relationship that is more than 50-fold higher than the average value
of 750 kb/cM of the tomato genome. An integrated cytogenetic-molecular map of chromosome 6 is presented that provides a framework
for physical mapping.
Received: 24 July 1998 / Accepted: 14 August 1998 相似文献
15.
Mesbah LA Kneppers TJ Takken FL Laurent P Hille J Nijkamp HJ 《Molecular & general genetics : MGG》1999,261(1):50-57
The Alternaria stem canker disease of tomato is caused by the necrotrophic fungal pathogen Alternaria alternata f. sp. lycopersici (AAL). The fungus produces AAL toxins that kill the plant tissue. Resistance to the fungus segregates as a single locus, called
Asc, and has been genetically mapped on chromosome 3 of tomato. We describe here the establishment of a 1383-kb YAC contig covering
the Asc locus and a series of plants selected for recombination events around the Asc locus. It was shown that the YAC contig corresponds to a genetic distance of at least 11.2 cM. Thus, the recombination rate
in the Asc region is six times higher (123 kb/cM) than the average for the tomato genome. Furthermore, the Asc locus could be localised to a 91-kb fragment, thus paving the way for the cloning and identification of the Asc gene(s) by complementation.
Received: 31 July 1998 / Accepted: 6 October 1998 相似文献
16.
Construction and characterization of a bacterial artificial chromosome library of apple 总被引:8,自引:0,他引:8
B. A. Vinatzer H.-B. Zhang S. Sansavini 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1998,97(7):1183-1190
A bacterial artificial chromosome (BAC) library has been constructed from apple (Malus×domestica Borkh.) using the variety “Florina”, which is resistant to scab (Venturia inaequalis) by virtue of the Vf gene. Since apple leaves are rich in polyphenols, high-molecular-weight DNA was extracted from leaf nuclei with a protocol
adapted to apple. The nuclei were then embedded in agarose microbeads and partially digested by varying ratios of EcoRI to EcoRI methylase. The resulting DNA fragments were size-selected by pulsed-field gel electrophoresis, ligated to the BAC cloning
vector pECBAC1 and transformed into Escherichia coli cells by electroporation. A total of 36 864 recombinant clones (BACs) were obtained. The library has an average insert size
of 120 kb and represents approximately 5×apple haploid-genome equivalents. It was screened with six cDNA probes using the
chemiluminescent DIG system. An average of 4.4 clones was detected for each locus. The apple BAC library will be used to isolate
the Vf scab resistance gene through map-based cloning. In this connection the library was screened with a marker closely linked
to the Vf gene and six positive clones have been isolated. This library should thus be well suited for map-based gene cloning, in particular
for the isolation of the Vf gene and for the construction of a physical map of the apple genome.
Received: 19 February 1998 / Accepted: 30 April 1998 相似文献
17.
Shiina T Shimizu C Oka A Teraoka Y Imanishi T Gojobori T Hanzawa K Watanabe S Inoko H 《Immunogenetics》1999,49(5):384-394
Class I genomic clones of the quail (Coturnix japonica) major histocompatibility complex (MhcCoja) were isolated and characterized. Two clusters spanning the 90.8 kilobase (kb) and 78.2 kb class I gene regions were defined
by overlapping cosmid clones and found to contain at least twelve class I loci. However, unlike in the chicken Mhc, no evidence for the existence of any Coja class II gene was obtained in these two clusters. Based on comparative analysis of the genomic sequences with those of the
cDNA clones, Coja-A, Coja-B, Coja-C, and Coja-D (Shiina et al. 1999), these twelve loci were assigned to represent one Coja-A gene, two Coja-B genes (Coja-B1 and -B2), four Coja-C genes (Coja-C1-C4), four Coja-D genes (Coja-D1-D4), and one new Coja-E gene. A class I gene-rich segment of 24.6 kb in which five of these genes (Coja-B1, -B2, -D1, -D2 and -E) are densely packed were sequenced by the shotgun strategy. All of these five class I genes are very compact in size [2089
base pairs (bp)–2732 bp] and contain no apparent genetic defect for functional expression. A transporter associated with the
antigen processing (TAP) gene was identified in this class I gene-rich segment. These results suggest that the quail class I region is physically
separated from the class II region and characterized by a large number of the expressible class I loci (at least seven) in
contrast to the chicken Mhc, where the class I and class II regions are not clearly differentiated and only at most three expressed class I loci so far
have been recognized.
Received: 9 March 1998 / Revised: 12 October 1998 相似文献
18.
Resistance gene analogues from rice: cloning, sequencing and mapping 总被引:18,自引:0,他引:18
R. Mago S. Nair M. Mohan 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1999,99(1-2):50-57
Degenerate oligonucleotide primers were designed on the basis of nucleotide-binding-site (NBS) motifs conserved between resistance
genes of Arabidopsis, flax and tobacco and subsequently used as PCR primers to amplify resistance gene analogues (RGA) in rice. Primers amplified
a major band of approximately 500 bp. Restriction analysis of the amplified product revealed that the band was made up of
several different fragments. Many of these fragments were cloned. Sixty different cloned fragments were analysed and assigned
to 14 categories based on Southern blot analysis. Fourteen clones, each representing one of the 14 categories of RGAs were
mapped onto the rice genetic map using a Nipponbare ( japonica)בKasalath’ (indica) mapping population consisting of 186 F2 lines. Of the 14 clones representing each class 12 could be mapped onto five different chromosomes of rice with a major cluster
of 8 RGAs on chromosome 11. Our results indicate that it is possible to use sequence homology from conserved motifs of known
resistance genes to amplify candidate resistance genes from diverse plant taxa.
Received: 23 September 1998 / Accepted: 28 November 1998 相似文献
19.
A bacterial artificial chromosome (BAC) library has been established for Arabidopsis thaliana (ecotype Col-0) covering about seven haploid nuclear genome equivalents. This library, called the Institut für Genbiologische
Forschung (IGF) BAC library, consists of 10 752 recombinant clones carrying inserts (generated by partial EcoRI digestion) of an average size of about 100 kb in a modified BAC vector, pBeloBAC-Kan. Hybridization with organellar DNA
and nuclear repetitive DNA elements revealed the presence of 1.1% clones with mitochondrial DNA, 0.2% clones with plastid
DNA, 3.2% clones with the 180 bp paracentromeric repeat, 1.6% clones with 5S rDNA, and 10.8% clones with the 18S-25S rDNA
repeat. With its extensive genome coverage, its rather uniformly sized inserts (80 kb <85% <120 kb) and low contamination
with organellar DNA, this library provides an excellent resource for A. thaliana genomic mapping, map-based gene cloning, and genome sequencing.
Received: 26 November 1997 / Accepted: 19 February 1998 相似文献
20.
S. Nakamura S. Asakawa N. Ohmido K. Fukui N. Shimizu S. Kawasaki 《Molecular & general genetics : MGG》1997,254(6):611-620
We constructed a rice Bacterial Artificial Chromosome (BAC) library from green leaf protoplasts of the cultivar Shimokita
harboring the rice blast resistance gene Pi-ta. The average insert size of 155 kb and the library size of seven genome equivalents make it one of the most comprehensive
BAC libraries available, and larger than many plant YAC libraries. The library clones were plated on seven high density membranes
of microplate size, enabling efficient colony identification in colony hybridization experiments. Seven percent of clones
carried chloroplast DNA. By probing with markers close to the blast resistance genes Pi-ta
2
(closely linked to Pi-ta) and Pi-b, respectively located in the centromeric region of chromosome 12 and near the telomeric end of chromosome 2, on average 2.2 ± 1.3
and 8.0 ± 2.6 BAC clones/marker were isolated. Differences in chromosomal structures may contribute to this wide variation
in yield. A contig of about 800 kb, consisting of 19 clones, was constructed in the Pi-ta
2
region. This region had a high frequency of repetitive sequences. To circumvent this difficulty, we devised a “two-step walking”
method. The contig spanned a 300 kb region between markers located at 0 cM and 0.3 cM from Pi-ta
2
. The ratio of physical to genetic distances (> 1,000 kb/cM) was more than three times larger than the average of rice (300
kb/cM). The low recombination rate and high frequency of repetitive sequences may also be related to the near centromeric
character of this region. Fluorescent in situ hybridization (FISH) with a BAC clone from the Pi-b region yielded very clear signals on the long arm of chromosome 2, while a clone from the Pi-ta
2
region showed various cross-hybridizing signals near the centromeric regions of all chromosomes.
Received: 14 August 1996 / Accepted: 2 December 1996 相似文献