Identification of RFLP markers linked to a gene for downy mildew resistance (Sdm) in sorghum

1996 ◽  
Vol 74 (2) ◽  
pp. 315-317 ◽  
Author(s):  
Boung-Jun Oh ◽  
Richard A. Frederiksen ◽  
Clint W. Magill

The Sdm locus in sorghum accession SC325 confers resistance to downy mildew caused by pathotypes 1 and 3 of Peronosclerospora sorghi. Restriction fragment length polymorphism linkage analysis placed the Sdm locus near loci detected by probes pSbTXS552 and pSbTXS361 at 5.0 and 7.9 cM, respectively. Fragment patterns for the cross segregating for disease resistance differed from those for the original mapping cross, preventing assignment of Sdm to a linkage group. Keywords: Peronosclerospora sorghi, resistance, RFLP, linkage, hybrid breeding.

Genome ◽  
2002 ◽  
Vol 45 (1) ◽  
pp. 133-146 ◽  
Author(s):  
L P Zhang ◽  
A Khan ◽  
D Niño-Liu ◽  
M R Foolad

A molecular linkage map of tomato was constructed based on a BC1 population (N = 145) of a cross between Lycopersicon esculentum Mill. line NC84173 (maternal and recurrent parent) and Lycopersicon hirsutum Humb. and Bonpl. accession PI126445. NC84173 is an advanced breeding line that is resistant to several tomato diseases, not including early blight (EB) and late blight (LB). PI126445 is a self-incompatible accession that is resistant to many tomato diseases, including EB and LB. The map included 142 restriction fragment length polymorphism (RFLP) markers and 29 resistance gene analogs (RGAs). RGA loci were identified by PCR amplification of genomic DNA from the BC1 population, using ten pairs of degenerate oligonucleotide primers designed based on conserved leucine-rich repeat (LRR), nucleotide binding site (NBS), and serine (threonine) protein kinase (PtoKin) domains of known resistance genes (R genes). The PCR-amplified DNAs were separated by denaturing polyacrylamide gel electrophoresis (PAGE), which allowed separation of heterogeneous products and identification and mapping of individual RGA loci. The map spanned 1469 cM of the 12 tomato chromosomes with an average marker distance of 8.6 cM. The RGA loci were mapped to 9 of the 12 tomato chromosomes. Locations of some RGAs coincided with locations of several known tomato R genes or quantitative resistance loci (QRLs), including Cf-1, Cf-4, Cf-9, Cf-ECP2, rx-1, and Cm1.1 (chromosome 1); Tm-1 (chromosome 2); Asc (chrromosme 3); Pto, Fen, and Prf (chromosome 5); OI-1, Mi, Ty-1, Cm6.1, Cf-2, CF-5, Bw-5, and Bw-1 (chromosome 6); I-1, I-3, and Ph-1 (chromosome 7); Tm-2a and Fr1 (chromosome 9); and Lv (chromosome 12). These co-localizations indicate that the RGA loci were either linked to or part of the known R genes. Furthermore, similar to that for many R gene families, several RGA loci were found in clusters, suggesting their potential evolutionary relationship with R genes. Comparisons of the present map with other molecular linkage maps of tomato, including the high density L. esculentum × Lycopersicon pennellii map, indicated that the lengths of the maps and linear order of RFLP markers were in good agreement, though certain chromosomal regions were less consistent than others in terms of the frequency of recombination. The present map provides a basis for identification and mapping of genes and QTLs for disease resistance and other desirable traits in PI126445 and other L. hirsutum accessions, and will be useful for marker-assisted selection and map-based gene cloning in tomato.Key words: disease resistance, genetic marker, molecular map, quantitative trait locus (QTL), restriction fragment length polymorphism (RFLP), RGAs.


Genetics ◽  
1987 ◽  
Vol 116 (2) ◽  
pp. 331-337
Author(s):  
Benoit S Landry ◽  
Rick V Kesseli ◽  
Barry Farrara ◽  
Richard W Michelmore

ABSTRACT A detailed linkage map of lettuce was constructed using 53 genetic markers including 41 restriction fragment length polymorphism (RFLP) loci, five downy mildew resistance genes, four isozyme loci and three morphological markers. The genetic markers were distributed into nine linkage groups and cover 404 cM which may be 25-30% of the lettuce genome. The majority (31 of 34) of the RFLP probes detected single segregating loci, although seven of these may have been homologous to further monomorphic loci. When several loci were detected by a single probe, the loci were generally linked, suggesting tandem duplications. One probe, however, detected loci in three linkage groups suggesting translocations. The five downy mildew resistance genes (Dm1, Dm3, Dm4, Dm5/8 and Dm13), segregating in the Calmar × Kordaat cross, represented each of the four resistance gene linkage groups. Dm5/8 is flanked by two cDNA loci, each located 10 cM away. These flanking markers will be used to study the source of variation in downy mildew genes and are also part our strategy to clone resistance genes.


Genome ◽  
2001 ◽  
Vol 44 (3) ◽  
pp. 401-412 ◽  
Author(s):  
X -F. Ma ◽  
K Ross ◽  
J P Gustafson

Using wheat ditelosomic lines and in situ hybridization of biotin-labelled DNA probes, 18 restriction fragment length polymorphism (RFLP) markers were physically located on homoeologous groups 1 and 3 chromosomes of wheat. Most of the markers hybridized to chromosome arms in a physical order concordant with the genetic maps. A majority of the markers studied were clustered in non-C-banded, distal euchromatic areas, indicating the presence of recombination hot spots and cold spots in those regions. However, on 1BS the markers were well dispersed, which could be due to the abundance of heterochromatin throughout the arm. An inversion between Xpsr653 and Xpsr953 was observed on 1AL. One new Xpsr688 locus, approximately 20–26% from the centromere, was found on 1AS and 1BS. The physical location of Xpsr170 on group 3 chromosomes probably represents an alternative to the loci on the genetic map. Finally, Xpsr313 was mapped to two physical loci on 1DL. Five markers were located to bins consistent with the deletion-based physical maps.Key words: wheat, physical mapping, in situ hybridization.


Author(s):  
G.F. Monakhos ◽  
S.G. Monakhos ◽  
R.R. Alizhanova

На Селекционной станции имени Н.Н. Тимофеева гибридизацией с донором устойчивости к пероноспорозу F1 Santero, беккроссом, инбридингом и отбором на инфекционном фоне с помощью молекулярного маркера DMR1 создано 15 линий лука репчатого гомозиготного по гену устойчивости Pd1. Оценка в однолетней культуре позволила выделить линии с массой луковиц 100120 г с высокой сохранностью, которые могут быть использованы в селекции F1 гибридов в качестве отцовских компонентов.Fifteen homozygous for Pd1 downy mildew resistance gene onion lines were developed by hybridization followed backcrossing F1 Santero of downy mildew resistant onion accession of European origin and a collection of onion inbred lines from LC Breeding station after N.N. Timofeev. The resistant to downy mildew, caused by Peronospora destructor (Berk.), plants were selected in segregated populations based on disease resistance test and molecular genotyping using DMR1marker. The lines with a mass of bulbs 100 120 g with high preservation, which can be used in the selection of F1 hybrids as paternal components.


Genome ◽  
2006 ◽  
Vol 49 (1) ◽  
pp. 30-41 ◽  
Author(s):  
J A Christianson ◽  
S R Rimmer ◽  
A G Good ◽  
D J Lydiate

Blackleg disease of crucifers, caused by the fungus Leptosphaeria maculans, is a major concern to oilseed rape producers worldwide. Brassica species containing the B genome have high levels of resistance to blackleg. Brassica juncea F2 and first-backcross (B1) populations segregating for resistance to a PG2 isolate of L. maculans were created. Segregation for resistance to L. maculans in these populations suggested that resistance was controlled by two independent genes, one dominant and one recessive in nature. A map of the B. juncea genome was constructed using segregation in the F2 population of a combination of restriction fragment length polymorphism (RFLP) and microsatel lite markers. The B. juncea map consisted of 325 loci and was aligned with previous maps of the Brassica A and B genomes. The gene controlling dominant resistance to L. maculans was positioned on linkage group J13 based on segregation for resistance in the F2 population. This position was confirmed in the B1 population in which the resistance gene was definitively mapped in the interval flanked by pN199RV and sB31143F. The provisional location of the recessive gene controlling resistance to L. maculans on linkage group J18 was identified using a subset of informative F2 individuals.Key words: blackleg, B genome, phoma, recessive resistance.


2002 ◽  
Vol 65 (1) ◽  
pp. 167-171 ◽  
Author(s):  
B. Z. GUO ◽  
A. BUTRON ◽  
H. LI ◽  
N. W. WIDSTROM ◽  
R. E. LYNCH

Aflatoxin, produced by Aspergillus flavus, is one of the most toxic and carcinogenic substances known and contaminates many agricultural commodities such as corn, peanuts, cottonseed, and tree nuts. The challenge to breeders/plant pathologists is to identify lines that have resistance to aflatoxin production. Maize population GT-MAS:gk has been identified and released as a germplasm with resistance to aflatoxin contamination. In the present study, we assessed genetic divergence in the GT-MAS:gk population using restriction fragment length polymorphism (RFLP) DNA markers to survey 11 selfed inbred lines and conducted field evaluations for the dissimilarities in aflatoxin production among these inbred lines in comparison with a sister population, GT-MAS:pw,nf. The 11 selfed inbred lines were assayed for DNA polymorphism using 113 RFLP markers in 10 linkage groups covering 1,518.2 centimorgans (cM; unit of gene or chromosome size). Considerable variation among the inbreds was detected with RFLP markers, of which 42 probe-enzyme combinations gave 102 polymorphic bands. Cluster analysis based on genetic similarities revealed associations and variations among the tested lines. Three polymorphic groups were distinguished by cluster analysis. Two years of field evaluation data showed that aflatoxin concentrations among the lines were significantly different in both years (P < 0.001). Maturity data were also different. Thus, this study demonstrates that the maize population GT-MAS:gk is heterogeneous and that individuals may be different in resistance to A. flavus infection and aflatoxin production. Therefore, the most resistant lines should be inbred to increase homogeneity, and resistance should be confirmed through progeny testing.


2001 ◽  
Vol 31 (1) ◽  
pp. 15-19 ◽  
Author(s):  
Camile Pizeta Semighini ◽  
Guillaume Delmas ◽  
Steven Park ◽  
Donald Amstrong ◽  
David Perlin ◽  
...  

Genome ◽  
2001 ◽  
Vol 44 (2) ◽  
pp. 242-248 ◽  
Author(s):  
Seliina Päällysaho ◽  
Susanna Huttunen ◽  
Anneli Hoikkala

We have identified six restriction fragment length polymorphism (RFLP) markers based on unique gene sequences on the X chromosome of Drosophila virilis and D. littoralis. The markers were localized by in situ hybridization on larval polytene chromosomes, and the conjugation of the X chromosomes of the two species was studied in salivary glands of interspecific hybrid female larvae. The gene arrangement of D. virilis and D. littoralis appeared to be very different at the proximal end of the X chromosome preventing recombination between RFLP markers located in this area. Simple quantitative trait loci (QTL) analysis showed that five of our marker genes (including nonA and Dmca1A, previously found to affect male courtship song in D. melanogaster) are linked with a gene(s) having a major effect on species differences in the male courtship song between D. virilis and D. littoralis. This shows that the song gene(s) may be located inside a large X-chromosomal inversion in D. littoralis (as previously suggested), but that it may also be located on an area between this inversion and the centromere, close to nonA and Dmca1A. Localization of this gene or gene complex will be continued with the aid of our newly identified RFLP markers by making interspecific crosses between D. virilis group species with more similar X chromosomes.Key words: restriction fragment length polymorphism (RFLP), in situ hybridization, Drosophila virilis.


1996 ◽  
Vol 121 (6) ◽  
pp. 996-1001 ◽  
Author(s):  
S.E. Gardiner ◽  
H.C.M. Bassett ◽  
C. Madie ◽  
D.A.M. Noiton

Information about a rare allele of phosphoglucomutase (PGM) that is shared by `Braeburn' and 16% of cultivars in the New Zealand Cultivar Collection was combined with historical information about cultivar distribution to select a set of 15 cultivars for a more detailed genetic analysis of their relatedness to the key New Zealand apple (Malus domestica Borkh.) `Braeburn'. DNA from all 16 cultivars was examined by RFLP analysis using 41 probe-enzyme combinations and also by RAPD analysis with 39 selected primers. The RFLP and RAPD data excluded a proposal that `Lady Hamilton' and `Braeburn' are genetically identical. All cultivars except `Lady Hamilton' were excluded as potential parents for `Braeburn' based on incompatible RFLP banding. Assessment of genetic distances between `Braeburn' and the other 15 cultivars from RFLP and RAPD data demonstrated that `Lady Hamilton' was more closely related to `Braeburn' than all others. We conclude that there is a high likelihood that `Lady Hamilton' is one of the parents of `Braeburn'.


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