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1.
A Genetic linkage map of Pinyon pine (Pinus edulis) based on amplified fragment length polymorphisms 总被引:1,自引:0,他引:1
S. E. Travis K. Ritland T. G. Whitham P. Keim 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1998,97(5-6):871-880
Amplified fragment length polymorphisms (AFLP) were used to rapidly generate a dense linkage map for pinyon pine (Pinus edulis). The map population consisted of 40 megagametophytes derived from one tree at Sunset Crater, Arizona. A total of 78 primer
combinations, each with three to five selective nucleotides, amplified 542 polymorphic markers. Of these, 33 markers showed
significant deviation from the expected Mendelian genotypic segregation ratio of 1 : 1, and 164 showed complete linkage with
another marker. This resulted in 338 unique markers mapping to 25 linkage groups, each of which ranged from 2 to 22 markers,
averaging 80 centiMorgans (cM) in size and covering 2,012 cM (2,200 cM with the inclusion of 25 cM for each of 7 unlinked
markers). Pairwise linkage values gave a genome size estimate of 2,390 cM, suggesting comprehensive coverage of the genome.
A search for subsets of primer combinations giving the best map coverage found 10 primer combinations which together marked
72% of the linkage map to within 10 cM; an additional 10 primer combinations increased this percentage to 85%. Our map represents
an initial step towards the identification of quantitative trait loci associated with pest resistance and water stress in
pinyons and will further allow us to examine introgression rates between P. edulis and P. californiarum.
Received: 14 October 1997 / Accepted: 29 April 1998 相似文献
2.
K. J. Williams A. Lichon P. Gianquitto J. M. Kretschmer A. Karakousis S. Manning P. Langridge H. Wallwork 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1999,99(1-2):323-327
Spot form of net blotch (SFNB) (Pyrenophora teres f maculata) is an economically damaging foliar disease of barley in many of the world’s cereal growing areas. The development of SFNB-resistant
cultivars may be accelerated through the use of molecular markers. A screen for SFNB resistance in 96 lines identified four
new sources of resistance, including a feed variety, ‘Galleon’, for which a fully mapped doubled haploid population was available.
Segregation data indicated SFNB resistance was conferred by a single gene in the ‘Galleon’בHaruna Nijo’ cross, positioned
on the long arm of chromosome 7H. This gene is designated Rpt4 and is flanked by the RFLP loci Xpsr117(D) and Xcdo673 at distances of 6.9 cM and 25.9 cM, respectively. The marker Xpsr117(D) was validated using another population segregating for Rpt4, correctly predicting SFNB resistance with more than 90% accuracy.
Received: 24 September 1998 / Accepted: 19 December 1998 相似文献
3.
G. Bonnema D. Schipper S. van Heusden P. Lindhout P. Zabel 《Molecular & general genetics : MGG》1997,253(4):455-462
A detailed map of part of the short arm of chromosome 1 proximal to the Cf-4/Cf-9 gene cluster was generated by using an F2 population of 314 plants obtained from the cross between the remotely related species Lycopersicon esculentum and L. peruvianum. Six markers that cosegregate in an L. esculentum×L. pennellii F2 population showed high recombination frequencies in the present interspecific population, spanning an interval of approximately
13 cM. Physical distances between RFLP markers were estimated by pulsed field gel electrophoresis of high-molecular-weight
DNA and by identifying YACs that recognized more than one RFLP marker. In this region 1 cM corresponded to 55–110 kb. In comparsion
with the value of 730 kb per cM averaged over the entire genome, this reflects the remarkably high recombination frequencies
in this region in the hybrid L. esculentum×L. peruvianum progeny population. The present data underline the fact that recombination is not a process that occurs randomly over the
entire genome, but can vary dramatically in intensity between chromosomal regions and among populations.
Received: 20 May 1996 / Accepted: 10 September 1996 相似文献
4.
A genetic linkage map of cowpea (Vigna unguiculata) developed from a cross between two inbred, domesticated lines 总被引:1,自引:0,他引:1
C. M. Menéndez A. E. Hall P. Gepts 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1997,95(8):1210-1217
We have constructed a genetic linkage map within the cultivated gene pool of cowpea (2n=2x=22) from an F8 recombinant inbred population (94 individuals) derived from a cross between the inbreds IT84S-2049 and 524B. These breeding
lines, developed in Nigeria and California, show contrasting reactions against several pests and diseases and differ in several
morphological traits. Parental lines were screened with 332 random RAPD decamers, 74 RFLP probes (bean, cowpea and mung bean
genomic DNA clones), and 17 AFLP primer combinations. RAPD primers were twice as efficient as AFLP primers and RFLP probes
in detecting polymorphisms in this cross. The map consists of 181 loci, comprising 133 RAPDs, 19 RFLPs, 25 AFLPs, three morphological/classical
markers, and a biochemical marker (dehydrin). These markers identified 12 linkage groups spanning 972 cM with an average distance
of 6.4 cM between markers. Linkage groups ranged from 3 to 257 cM in length and included from 2 to 41 markers, respectively.
A gene for earliness was mapped on linkage group 2. Seed weight showed a significant association with a RAPD marker on linkage
group 5. This map should facilitate the identification of markers that “tag” genes for pest and disease resistance and other
traits in the cultivated gene pool of cowpea.
Received: 16 September 1996 / Accepted: 25 April 1997 相似文献
5.
Z. M. Wang K. M. Devos C. J. Liu R. Q. Wang M. D. Gale 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1998,96(1):31-36
An RFLP-based map consisting of 160 loci was constructed in an intervarietal cross of foxtail millet [Setaria italica (L.) P. Beauv.], Longgu 25×Pagoda Flower Green. The map comprises nine linkage groups, which were aligned with the nine foxtail
millet chromosomes using trisomic lines, and spans 964 cM. The intraspecific map was compared to an interspecific map, constructed
in a S. italica×S. viridis cross. Both the order of the markers and the genetic distances between the loci were highly conserved. Deviations from the
expected 1 : 2 : 1 Mendelian segregation ratios were observed in both the intra- and inter-specific populations. The segregation
data indicate that chromosome VIII in the Longgu 25×Pagoda Flower Green cross carries a gene that strongly affects gamete
fertility.
Received: 18 December 1996 / Accepted: 4 August 1997 相似文献
6.
Construction of an RFLP linkage map for cultivated sunflower 总被引:5,自引:0,他引:5
C. C. Jan B. A. Vick J. F. Miller A. L. Kahler E. T. Butler III. 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1998,96(1):15-22
An RFLP linkage map was constructed for cultivated sunflower Helianthus annuus L., based on 271 loci detected by 232 cDNA probes. Ninety-three F2 plants of a cross between inbred lines RHA 271 and HA 234 were used as the mapping population. These genetic markers plus
a fertility restoration gene, Rf
1, defined 20 linkage groups, covering 1164 cM of the sunflower genome. Of the 71 loci 202 had codominant genotypic segregation,
with the rest showing dominant segregation. Thirty-two of the 232 probes gave multiple locus segregation. There were 39 clusters
of tightly linked markers with 0 cM distance among loci. This map has an average marker-to-marker distance of 4.6 cM, with
11 markerless regions exceeding 20 cM.
Received: 17 June 1997 / Accepted: 19 June 1997 相似文献
7.
R. N. Morgan J. P. Wilson W. W. Hanna P. Ozias-Akins 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1998,96(3-4):413-420
Pearl millet [Pennisetum glaucum (L.) R.Br.] is a warm-season grass used for food, feed, fodder and forage, primarily in countries of Africa and India but
grown around the world. The two most-destructive diseases to pearl millet in the United States are rust (caused by Puccinia substriata var. indica) and pyricularia leaf spot (caused by Pyricularia grisea). Genes for disease resistance to both pathogens have been transferred into agronomically acceptable forage and grain cultivars.
A study was undertaken to identify molecular markers for three rust loci and one pyricularia resistance locus. Three segregating
populations were screened for RAPDs using random decamer primers and for RFLPs using a core set of probes detecting single-copy
markers on the pearl millet map. The rust resistance gene Rr
1
from the pearl millet subspecies P. glaucum ssp. monodii was linked 8.5 cM from the RAPD OP-G8350. The linkage of two RFLP markers, Xpsm108 (15.5 cM) and Xpsm174 (17.7 cM), placed the Rr
1
gene on linkage-group 3 of the pearl millet map. Rust resistance genes from both Tift 89D2 and ICMP 83506 were placed on linkage-group 4 by determining genetic linkage to the RFLP marker Xpsm716 (4.9 and 0.0 cM, respectively). Resistance in ICMP 83506 was also linked to the RFLP marker Xpsm306 (10.0 cM), while resistance in Tift 89D2 was linked to RAPD markers OP-K19350 (8.8 cM) and OP-O8350 (19.6 cM). Fragments from OP-K19 and OP-O8 in the ICMP 83506 population, and Xpsm306 in the Tift 89D2 population, were monomorphic. Only one RAPD marker (OP-D11700, 5.6 cM) was linked to pyricularia leaf spot resistance. Attempts to detect polymorphisms with rice RFLP probes linked to
rice blast resistance (Pyricularia oryzae; syn=P. grisea) were unsuccessful.
Received: 19 May 1997 / Accepted: 21 October 1997 相似文献
8.
Identification of RAPD markers linked to a Phytophthora fragariae resistance gene (Rpf1) in the cultivated strawberry 总被引:2,自引:0,他引:2
K. M. Haymes B. Henken T. M. Davis W. E. van de Weg 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1997,94(8):1097-1101
Bulked segregant analysis (BSA) was used to identify seven random amplified polymorphic DNA (RAPD) markers linked to the
Rpf 1 gene. Rpf 1 confers resistance to Phytophthora fragariae var. fragariae, the causal agent of red stele root rot in Fragaria spp. The bulked DNAs represented subsets of a F1 population obtained from the cross Md683×Senga Sengana which consisted of 60 plants and segregated in a 1:1 ratio for resistance
or susceptibility to race 2.3.4 isolate NS2 of P. fragariae. Seven markers were shown to be linked to Rpf 1 and were generated from four primers; five of these markers were in coupling phase and two in repulsion phase with respect
to the gene. A linkage map of this resistance gene region was generated using JoinMap 2.0TM. The manner in which Rpf 1 and the linked markers co-segregated indicated that they are inherited in a disomic fashion. These markers could enable gene
pyramiding and marker-assisted selection of resistance genes in strawberry breeding programmes.
Received: 26 August 1996 / Accepted: 20 December 1996 相似文献
9.
A genetic map of melon (Cucumis melo L.) based on amplified fragment length polymorphism (AFLP) markers 总被引:3,自引:0,他引:3
Y.-H. Wang C. E. Thomas R. A. Dean 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1997,95(5-6):791-798
Genetic maps facilitate the study of genome structure and evolution, and the identification of monogenic traits or Mendelian
components of quantitative traits. We evaluated 228 RAPD, microsatellite and AFLP markers for linkage analysis in melon (Cucumis melo L.) varieties MR-1 (resistant to Fusarium wilt, powdery and downy mildews) and Ananas Yokneum (AY; susceptible to these diseases) and constructed a detailed genetic
map. The mapping population consisted of 66 backcross progenies derived from AY×(MR-1×AY). Despite a relatively low level
of polymorphism in the species, AFLP markers were found to be more efficient in mapping the melon genome than RAPD or microsatellite
markers. The map contains 197 AFLPs, six RAPDs and one microsatellite marker assigned to 14 major and six minor linkage groups,
and covers 1942 cM with the average distance between adjacent markers of approximately 10 cM. The maximum distance allowed
between markers is 27.5 cM. About 11% of the intervals (20 out of 173) are over 20 cM (but less than 27.5 cM). The map has
immediate utility for identifying markers linked to disease resistance genes that are suitable for marker-assisted breeding.
The use of microsatellite markers for integration with other maps is also discussed.
Received: 12 March 1997 / Accepted: 20 May 1997 相似文献
10.
Development of RAPD and SCAR markers linked to the Russian wheat aphid resistance gene Dn2 in wheat 总被引:5,自引:0,他引:5
A. A. Myburg M. Cawood B. D. Wingfield A.-M. Botha 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1998,96(8):1162-1169
RAPD (random amplified polymorphic DNA) analysis was used to identify molecular markers linked to the Dn2 gene conferring resistance to the Russian wheat aphid (Diuraphis noxia Mordvilko). A set of near-isogenic lines (NILs) was screened with 300 RAPD primers for polymorphisms linked to the Dn2 gene. A total of 2700 RAPD loci were screened for linkage to the resistance locus. Four polymorphic RAPD fragments, two in
coupling phase and two in repulsion phase, were identified as putative RAPD markers for the Dn2 gene. Segregation analysis of these markers in an F2 population segregating for the resistance gene revealed that all four markers were closely linked to the Dn2 locus. Linkage distances ranged from 3.3 cM to 4.4 cM. Southern analysis of the RAPD products using the cloned RAPD markers
as probes confirmed the homology of the RAPD amplification products. The coupling-phase marker OPB10880c and the repulsion-phase marker OPN1400r were converted to sequence characterized amplified region (SCAR) markers. SCAR analysis of the F2 population and other resistant and susceptible South African wheat cultivars corroborated the observed linkage of the RAPD
markers to the Dn2 resistance locus. These markers will be useful for marker-assisted selection of the Dn2 gene for resistance breeding and gene pyramiding.
Received: 1 July 1997 / Accepted: 20 October 1997 相似文献
11.
S. C. K. Milach H. W. Rines R. L. Phillips 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1997,95(5-6):783-790
Restriction fragment length polymorphism (RFLP) analysis provides a valuable tool for characterizing and understanding relationships
among genes for useful traits in crop species, particularly in ones with complex genomes such as the hexaploid cultivated
oat Avena sativa L. (2n=6x=42). Using Bulked Segregant Analysis (BSA) and F2 RFLP linkage data, we mapped three dominant oat dwarfing loci to different regions of the oat genome. Dw6, in oat line OT207, is 3.3±1.3 cM from the Xumn145B locus, which has not been placed on the hexaploid oat linkage map. Dw7, in line NC2469-3, is 4.3±2.3 cM from Xcdo1437B and 33±4.1 cM from Xcdo708B. This places Dw7 to linkage group 22. Dw8, in the Japanese lines AV17/3/10 and AV18/2/4, mapped 4.9±2.2 cM from Xcdo1319A in an AV17/3/10בKanota’ F2 population and 6.6±2.6 cM from it in an AV18/2/4בKanota’ population. This places Dw8 to linkage group 3. Aneuploid analysis of markers linked to the dwarfing genes located Dw6 on the smallest oat chromosome (chromosome 18) and Dw7 on the longest satellited chromosome (chromosome 19). The RFLP markers closely linked to the three dwarfing genes identify
distinct regions of the oat genome that contribute to plant height and they should be useful in characterizing new genetic
sources of dwarfness in oat.
Received: 8 May 1997 / Accepted: 20 May 1997 相似文献
12.
J. P. W. Haanstra C. Wye H. Verbakel F. Meijer-Dekens P. van den Berg P. Odinot A. W. van Heusden S. Tanksley P. Lindhout J. Peleman 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1999,99(1-2):254-271
Two independent F2 populations of Lycopersicon esculentum×L. pennellii which have previously been investigated in RFLP mapping studies were used for construction of a highly saturated integrated
AFLP map. This map spanned 1482 cM and contained 67 RFLP markers, 1078 AFLP markers obtained with 22 EcoRI+MseI primer combinations and 97 AFLP markers obtained with five PstI+MseI primer combinations, 231 AFLP markers being common to both populations. The EcoRI+MseI AFLP markers were not evenly distributed over the chromosomes. Around the centromeric region, 848 EcoRI+ MseI AFLP markers were clustered and covered a genetic distance of 199 cM, corresponding to one EcoRI+ MseI AFLP marker per 0.23 cM; on the distal parts 1283 cM were covered by 230 EcoRI+MseI AFLP markers, corresponding to one marker per 5.6 cM. The PstI/MseI AFLP markers showed a more even distribution with 16 PstI/MseI AFLP markers covering a genetic distance of 199 cM around the centromeric regions and 81 PstI/MseI AFLP markers covering a genetic distance of 1283 cM on the more distal parts, corresponding to one marker per 12 and 16 cM
respectively. In both populations a large number of loci showed a significant skewed segregation, but only chromosome 10 loci
showed skewness that was similar for both populations. This ultra-dense molecular-marker map provides good perspectives for
genetic and breeding purposes and map-based cloning.
Received: 3 September 1998 / Accepted: 27 October 1998 相似文献
13.
L. Montesclaros N. Nicol E. Ubalijoro C. Leclerc-Potvin L. Ganivet J.-F. Laliberté M. G. Fortin 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1997,94(6-7):941-946
We have investigated the interaction between two different potyviruses and resistant cultivars of Lactuca sativa. Turnip mosaic virus (TuMV) and lettuce mosaic virus (LMV) were used to inoculate several cultivars under different temperature
regimes to characterize the resistance reaction. Resistance conferred by the recessive mo locus against LMV infection did not provide immunity. Virus accumulated in plant tissues to different levels depending on
the genetic background of the cultivar, suggesting that several genes were involved in the resistance phenotype. Under temperature
regimes that enhanced the hypersensitive reaction, resistant cultivars produced necrotic reactions. In contrast, resistance
to TuMV infection conferred by the dominant Tu locus resulted in complete immunity in the plant. No virus accumulated in inoculated leaves nor was any necrotic reaction
observed. The resistance loci were characterized at the genetic level by mapping them relative to molecular markers. Only
weak linkages could be identified to mo, again supporting the hypothesis that several genes are involved. The Tu locus was mapped in two different crosses relative to several markers, the closest two linked at less than 1 cM. A high-resolution
genetic map of the Tu locus was constructed by screening 500 F2 individuals for recombinants around that locus.
Received: 4 June 1996/Accepted: 15 November 1996 相似文献
14.
T. Komatsuda S. Kawasaki I. Nakamura F. Takaiwa F. Taguchi-Shiobara S. Oka 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1997,95(4):637-642
Recombinant backcross lines of barley were produced from a cross between Kanto Nakate Gold (KNG; two-rowed) and Azumamugi
(AZ; six-rowed) after backcrosses of F1 plants with AZ as the recurrent parent. Each of these lines had an introgressed segment from chromosome 2 of KNG. Two recombinant
backcross lines, L1 and M3-13, were used for an initial screening of polymorphism. After screening a total of 888 oligonucleotides
as arbitrary primers, we identified eight random amplified polymorphic DNAs (RAPDs) between backcross lines and AZ. Among
the RAPD fragments, CMNA-38700 was linked to the v locus with a recombination frequency of zero, while OPJ-09850 and OPP-02700 were linked to the v locus at a map distance of 1.4 cM. Thus, the three RAPD markers were clustered around the v locus since the lengths of introgressed chromosomal segments in the L1 and M3-13 lines were no less than 38 cM. The other
five RAPD fragments that we identified were not linked to the v locus.
Received: 14 January 1997 / Accepted: 14 February 1997 相似文献
15.
G. J. King F. H. Alston L. M. Brown E. Chevreau K. M. Evans F. Dunemann J. Janse F. Laurens J. R. Lynn C. Maliepaard A. G. Manganaris P. Roche H. Schmidt S. Tartarini J. Verhaegh R. Vrielink 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1998,96(5):699-708
Apple scab, caused by the fungus Venturia inaequalis (Cke.) Wint., is an important disease in commercial apple production. A mapping population of 155 individuals, derived from
a cross between the apple varieties ‘Prima’ (resistant)בFiesta’ (susceptible), was scored for response to the disease in
replicated field and glasshouse trials throughout Europe. Twenty data sets were selected and cluster analysis was used to
form a consensus score for the population fitting a 1 : 1 segregation ratio of resistance:susceptibility. The progeny were
scored with molecular markers. A detailed map covering 54 cM of the ‘Prima’ linkage group containing the Vf gene for scab resistance was constructed using 24 molecular markers linked to the resistance gene. One isoenzyme marker (Pgm-1), six RFLP markers and 17 RAPD markers formed a linkage group with the consensus measure of resistance to scab. Four marker
bridges were established with the corresponding ‘Fiesta’ linkage group with additional markers (one isozyme, one RFLP, three
RAPD and one AFLP). A low chi-square value indicated a good fit of the marker ordering, which was in close agreement with
previously reported linkage positions for some of the markers and Vf. Differences were observed in the ability of different scoring methods to resolve susceptible and resistant classes. The
results obtained for the consensus classification of resistance to scab for the population may suggest the presence of virulent
inocula at some sites, which could overcome the Vf gene for resistance. The consequences of relying on individual scoring occasions for studying Vf scab resistance are discussed in the context of linkage analysis, conventional breeding selection, and marker-assisted selection.
Received: 23 July 1997 / Accepted: 31 October 1997 相似文献
16.
J. E. Bradshaw C. A. Hackett R. C. Meyer D. Milbourne J. W. McNicol M. S. Phillips R. Waugh 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1998,97(1-2):202-210
Seventy eight clones from the cross between SCRI clone 12601ab1 and cv Stirling were used to explore the possibility of genetical
linkage analysis in tetraploid potato (Solanum tuberosum subsp. tuberosum). Clone 12601ab1 had quantitative resistance to Globodera pallida Pa2/3 derived from S. tuberosum subsp. andigena. The strategy adopted involved identifying single- (simplex) and double- (duplex) dose AFLP markers in the parents from segregation
ratios that could be unambiguously identified in their offspring, detecting linkage between a marker and a putative quantitative
trait locus (QTL) for resistance, and placing the QTL on the linkage map of markers. The numbers of scorable segregating markers
were 162 simplex ones present only in 12601ab1, 87 present in Stirling, and 32 present in both; and 72 duplex markers present
only in 12601ab1 and 45 present in Stirling. The total map length was 990.9 cM in 12601ab1 and 484.6 cM in Stirling. A QTL
with a resistance allele present in double dose (QQqq) in 12601ab1 was inferred from the associations between resistance scores
(square root of female counts) and two duplex markers linked in coupling, which, in turn, were linked in coupling to four
simplex markers also associated with resistance, but to a lesser degree. The largest marker class difference was the one for
the duplex marker P61M34=15. It accounted for 27.8% of the phenotypic variance in resistance scores, or approximately 30%
of the genotypic variance. Subsequently, this duplex marker was found to be linked in coupling with a duplex SSR allele Stm3016=a,
whose locus was shown to be on chromosome IV in a diploid reference mapping population. The other QTLs for resistance segregating
in the progeny were not identified for one or more of the following reasons: the markers did not cover the whole of the genome,
there were unfavourable repulsion linkages between the QTLs and markers, or the gene effects were not large enough to be detected
in an experiment of the size conducted. It is concluded that prospects appear good for detecting QTLs and using marker-assisted
selection in a tetraploid potato breeding programme, provided that, in future, the population size is increased to over 250
and more SSR markers are used to complement the AFLPs; the same is likely to be true for other autotetraploid crops.
Received: 16 December 1997 / Accepted: 4 March 1998 相似文献
17.
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
18.
RFLP and RAPD markers linked to the rosy leaf curling aphid resistance gene (Sd1) in apple 总被引:10,自引:0,他引:10
P. Roche F. H. Alston C. Maliepaard K. M. Evans R. Vrielink F. Dunemann T. Markussen S. Tartarini L. M. Brown C. Ryder G. J. King 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1997,94(3-4):528-533
Sd
1 is a dominant gene for resistance to biotypes 1 and 2 of the rosy leaf curling aphid, Dysaphis devecta Wlk., which can cause economic damage to apple trees. This report describes the identification of three RFLP and four RAPD
markers linked to Sd
1 in a cross between the D. devecta susceptible variety ‘Prima’ (sd
1
sd
1) and the resistant variety ‘Fiesta’ (Sd
1
sd
1). Potted trees were artificially infested in the glasshouse, and the ratio of resistant:susceptible plants supported the
hypothesis that the resistance was under the control of a single dominant gene. The position of the gene was mapped to a single
locus on a ‘Fiesta’ chromosome, within 2 cM of three tightly linked RFLP markers (MC064a, 2B12a and MC029b); the four RAPD
markers were located further away (between 13 and 46 cM). This is the first report of molecular markers for an aphid resistance
gene in tree fruit crops. The potential application of these markers in a marker-assisted resistance breeding programme is
discussed.
Received: 1 July 1996/Accepted: 23 August 1996 相似文献
19.
Resistance to submergence stress is an important breeding objective in areas where rice cultivars are subjected to complete
inundation for a week or more. The present study was conducted to develop a high-resolution map of the region surrounding
the submergence tolerance gene Sub1 in rice, which derives from the Indian cultivar FR13A. Submergence screening of 8-day-old plants of F3 families kept for 14 days submerged in 60 cm of water allowed an accurate classification of Sub1 phenotypes. Bulked segregant analysis was used to identify AFLP markers linked to Sub1. A population of 2950 F2 plants segregating for Sub1 was screened with two RFLP markers flanking the Sub1 locus, 2.4 and 4.9 cM away. Submergence tolerance was measured in the recombinant plants, and AFLP markers closely linked
to Sub1 were mapped. Two AFLP markers cosegregated with Sub1 in this large population, and other markers were localized within 0.2 cM of Sub1. The high-resolution map should serve as the basis for map-based cloning of this important locus, as it will permit the identification
of BAC clones spanning the region.
Received: 15 December 1999 / Accepted: 18 February 2000 相似文献
20.
Suppressed recombination around the MXC3 locus, a major gene for resistance to poplar leaf rust 总被引:8,自引:0,他引:8
B. Stirling G. Newcombe J. Vrebalov I. Bosdet H.D. Bradshaw Jr. 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》2001,103(8):1129-1137
A positional cloning strategy is being implemented in Populus for the isolation of the dominant MXC3 allele, which confers resistance to poplar leaf rust caused by Melampsora×columbiana (pathotype 3). AFLP markers were used to saturate the chromosomal region around the MXC3 locus in a large (n=1,902) Populus trichocarpa×P. deltoides (T×D) mapping pedigree segregating 1:1 for rust resistance and susceptibility. The high-resolution linkage map developed
around the MXC3 locus contains 19 AFLP markers and spans a genetic distance of 2.73 cM. Of the 19 AFLP markers, seven were found to co-segregate
with the locus. One co-segregating AFLP marker, CCG.GCT_01, was converted to an STS marker (BVS1) and used to identify a physical contig of overlapping BAC clones from the MXC3 region. Genetic and physical mapping of markers isolated from the BAC contig failed to delimit the MXC3 locus within a 300-kb interval defined by the overlapping BAC clones. This result indicates a >25-fold reduction in recombination
frequency in the MXC3 region compared to the average rate of recombination for the Populus genome.
Received: 8 December 2000 / Accepted: 1 March 2001 相似文献