Analysis of molecular markers associated with powdery mildew resistance genes in peach (Prunus persica (L.) Batsch)xPrunus davidiana hybrids

A progeny of 77 hybrids issued from a cross between two heterozygous Prunus, peach [P. persica (L.) Batsch] (variety Summergrand) and a related species, P. davidiana (clone 1908), was analysed for powdery mildew resistance in five independent experiments. This population was also analysed for its genotype with isoenzyme and RAPD markers in order to map the genes responsible for resistance. A genetic linkage map was generated for each parent. The Summergrand linkage map is composed of only four linkage groups including 15 RAPD markers and covering 83.1 centiMorgans (cM) of the peach nuclear genome, whereas the P. davidiana linkage map contains 84 RAPD markers and one isoenzyme assigned to ten linkage groups and covering 536 cM. Significant associations between molecular markers and powdery mildew resistance were found in each parent. For P. davidiana, one major QTL with a very strong effect and five other QTLs with minor effects were located in different linkage groups. For Summergrand, three QTLs for powdery mildew resistance, with minor effects, were also detected. Consequently, evidence is given here that the powdery mildew resistance of P. davidiana clone 1908 and P. persica variety Summergrand is not a monogenic character but is controlled by at least one major gene and several minor genes.     

The locus for apolipoprotein E (apoE) is close to the Lutheran (Lu) blood group locus on chromosome 19

Summary Linkage has been described between the loci for apolipoprotein E (apoE) and the complement C3 (C3) on chromosome 19. C3 is known to belong to a linkage group with gene order C3-Se-Lu. The present study revealed linkage between Se and apoE with peak lod score +3.3 at recombination fraction 0.08 in males and +1.36 at 0.22 in females, and linkage between apoE and Lu with lod score +4.52 at zero recombination in sexes combined. The C3-apoE linkage gives lod score +4.00 at = 0.18 in males, but +0.04 at =0.45 in females. Triple heterozygote families confirm that apoE is on the Se side and on the Lu side of C3. Allelic association between apoE and Lu has not been ruled out. Combining our data with published data on C3-Se and Se-Lu, this segment of chromosome 19 has an average sex ratio of female/male recombination of 2.3.     

Further evidence against linkage between christ-siemens-touraine (CST) and XG loci

Summary A Brazilian informative pedigree for the CST:XG linkage relationship is analysed. The present lods, together with those from previously published data, provide evidence for the exclusion of linkage until a value of around 0.34.     

A linkage map ofBrassica rapa (syn.campestris) based on restriction fragment length polymorphism loci

Summary A detailed linkage map ofB. rapa (syn.campestris) was constructed based on segregation of 280 restriction fragment length polymorphism loci, detected by using 188 genomic DNA clones as probes on DNAs from a F₂ population of Chinese cabbage MichihilF×Spring broccoli. These genetic markers covered 1,850 centiMorgans (cM) and defined ten linkage groups, which equals the haploid chromosome number of this species. Extensive sequence duplication was evident by the detection of two or more segregating loci with each of 69 clones (36.7% of the total). Although some duplicated loci were randomly distributed throughout the genome, many had linkage arrangements that were conserved on different linkage groups, suggesting that large chromosome fragments were present in multiple copies. However, conservation in the linkage arrangement of duplicate loci throughout entire pairs of linkage groups was not observed. Single-copy loci were often found to be located within conserved duplicated regions, and linkage distances between some loci having conserved duplicated arrangements were substantially different between the duplicated regions. Structural rearrangements, such as insertions, deletions, and inversions or combinations of these events, seemed to be related to the alternations of map distances between duplicated loci and to the dispersal of duplicated chromosome fragments. These results suggest thatB. rapa has evolved in part by duplication of chromosomes or large chromosome fragments with subsequent structural rearrangements.     

A newly discovered tRNA(1Asp) gene (aspV) of Escherichia coli K12

Summary We report a new tRNA ₁ ^Asp gene near the dnaQ gene, which is located at 5 min on the Escherichia coli linkage map. We named it aspV. The sequence corresponding to the mature tRNA is identical with that of the two previously identified tRNA ₁ ^Asp genes (aspT and aspU), but there is no homology in the sequences of their 3-and 5-flanking regions.Abbreviations kb kilo base pair(s) - rrn ribosomal RNA     

Genetic linkage relations of the sixth component of complement (C6)

Summary Linkage relations between the C6 and 33 other genetic marker loci have been analyzed in Norwegian pedigrees, including 114 matings with 388 informative children, by use of the MOSM computer program. No suggestion of linkage was found. Very close or close linkage (<0.06) has been ruled out for males between C6 and the following 19 marker loci: GPT, HLA+Bf, Rh, C3, Hp, PGM ₃, Km, Gm, Fy, Gc, AB0, Jk, GLO ₁, K, MNSs, PTC, ACP ₁, PGM ₁ and Pi. For several of the relations even loose linkage is unlikely.     

Autosomal dominant retinitis pigmentosa: a new multi-allelic marker (D3S621) genetically linked to the disease locus (RP4)

Summary We report the characterization of a new eightallele microsatellite (D3S621) isolated from a human chromosome 3 library. Two-point and multi-locus genetic linkage analysis have shown D3S621 to co-segregate with the previously mapped RP4 ( _m=0.12, Z _m=4.34) and with other genetic markers on the long arm of the chromosome, including D3S14 (R208) ( _m=0.00, Z _m= 15.10), D3S47 (C17) ( _m=0.11, Z _m=4.95), Rho ( _m= 0.07, Z _m=1.37), D3S21 (L182) ( _m=0.07, Z _m=2.40) and D3S19 (U1) ( _m=0.13, Z _m=2.78). This highly informative marker, with a polymorphic information content of 0.78, should be of considerable value in the extension of linkage data for autosomal dominant retinitis pigmentosa with respect to locii on the long arm of chromosome 3.     

Genetic fine localization of the arrestin (S-antigen) gene 4 cM distal from D2S172

Arrestin is a component of the light transduction cascade that takes place in the outer segment of retinal rods. In situ hybridization and linkage analysis have localized the arrestin gene to a region of 50 cM between CRYG and D2S23/D2S55 on chromosome 2q24–37. We have performed pairwise and multipoint linkage analysis between arrestin and four highly polymorphic markers from this region. The results indicate tight linkage between the gene and the microsatellite D2S172 (Z _max = 9.25 at =0.038). This fine localization of the gene should provide a useful tool for cosegregation analyses involving the arrestin gene.     

A new polymorphic marker (D10S97) tightly linked to the multiple endocrine neoplasia type 2A (MEN2A) locus

Familial multiple endocrine neoplasia type 2A (MEN 2A) is a cancer syndrome that is inherited as an autosomal dominant with high penetrance. Its clinical features are medullary carcinoma of the thyroid, pheochromocytomas, and hyperparathyroidism. A new polymorphic locus D10S97 (probe: KW6SacI) detects a codominant EcoRI polymorphism that is tightly linked to the MEN2A locus. The peak lod score for linkage between D10S97 with MEN2A is 13.03 at =0.00. The polymorphic locus D10S97 maps, by linkage analysis, into the previously defined interval between FNRB and RBP3 to which MEN2A has been assigned. We present physical mapping data showing that the probe pKW6 originates from 10p13 and that the polymorphic locus D10S97 in 10q11.2 is detected by cross-hybridization.     

Tightly linked di- and tri-nucleotide microsatellites do not evolve in complete independence: evidence from linked (TA)n and (TAA)n microsatellites of chickpea (Cicer arietinum L.)

In order to understand the dynamics of microsatellite evolution, we have studied allelic variation at a closely linked (TA) _n and (TAA) _n microsatellite loci in 114 land races of chickpea (Cicer arietinum L.), sampled worldwide. These two loci are separated by 27 bp. The two loci showed a very high degree of polymorphism and hence the combined length with the genetic diversity of 0.93, 0.90 and 0.98 for (TAA) _n , (TA) _n and the combined length, respectively. Using the variation data at the linked loci, a standardized index of linkage disequilibrium was also computed (I ^S _A =0.092), which tests the null hypothesis of no linkage and was significant, indicating the presence of linkage disequilibrium. Furthermore, the dynamics of allelic variation showed that there is a threshold combined length, below which both (TAA) _n and (TA) _n loci evolve independently, and above which, if one locus increase in size, the other closely linked locus has a tendency to decrease its size and vice versa, without change in the overall ratio of (TAA) _n and (TA) _n allele sizes at the region. This result indicates that there are processes in the cell, which read the combined size of the two loci both for proportion and length and determine the direction of tightly linked di- and tri-nucleotide repeat evolution.Communicated by R. Hagemann     

Isolation of molecular markers for tomato (L. esculentum) using random amplified polymorphic DNA (RAPD)

Summary A new DNA polymorphism assay was developed in 1990 that is based on the amplification by the polymerase chain reaction (PCR) of random DNA segments, using single primers of arbitrary nucleotide sequence. The amplified DNA fragments, referred to as RAPD markers, were shown to be highly useful in the construction of genetic maps (RAPD mapping). We have now adapted the RAPD assay to tomato. Using a set of 11 oligonucleotide decamer primers, each primer directed the amplification of a genome-specific fingerprint of DNA fragments. The potential of the original RAPD assay to generate polymorphic DNA markers with a given set of primers was further increased by combining two primers in a single PCR. By comparing fingerprints of L. esculentum, L. pennellii, and the L. esculentum chromosome 6 substitution line LA1641, which carries chromosome 6 from L. pennellii, three chromosome 6-specific RAPD markers could be directly identified among the set of amplified DNA fragments. Their chromosomal position on the classical genetic map of tomato was subsequently established by restriction fragment length polymorphism (RFLP) linkage analysis. One of the RAPD markers was found to be tightly linked to the nematode resistance gene Mi.     

Genetics of a tissue esterase polymorphism (Est-6) in the rabbit (Oryctolagus cuniculus)

Genetic analysis of a polymorphic tissue esterase revealed a new locus (Est-6) with two alleles (Est-6 ^a andEst-6 ^b) on linkage group VI of the rabbit.Est-6 is closely linked to theEst-1,2,4 cluster. Esterase ofEst-6 is found in many organs, particularly in liver and small intestine, but not in erythrocytes and serum.Est-6 esterase hydrolyzes -naphthyl acetate and butyrate, naphthol AS-D acetate, indoxyl acetate, and butyrate as well as 5-bromoindoxyl acetate,N-acetyl-l-alanine--naphthyl ester but not 4-methylumbelliferyl acetate and fluorescein diacetate. The enzyme is inhibited by bis-p-nitrophenyl phosphate and eserine but not byp-chloromercuribenzoate. It was classified as a carboxylesterase (EC 3.1.1.1). Based on chromosomal localization, tissue distribution, substrate specificity, inhibitor sensitivity, and range ofpI's, rabbitEst-6 is assumed to be homologous with mouseEs-7.The contribution of Dr. O. von Deimling (No. 59) was supported by the Deutsche Forschungsgemeinschaft (De 315/2-2).     

Molecular analysis of methane monooxygenase from Methylococcus capsulatus (Bath)

Methane monooxygenase (MMO) is the enzyme responsible for the conversion of methane to methanol in methanotrophic bacteria. In addition, this enzyme complex oxidizes a wide range of aliphatic and aromatic compounds in a number of potentially useful biotransformations. In this study, we have used biochemical data obtained from purification and characterization of the soluble MMO from Methylococcus capsulatus (Bath), to identify structural genes encoding this enzyme by oligonucleotide probing. The genes encoding the and subunits of MMO were found to be chromosomally located and were linked in this organism. We report here on the analysis of a recombinant plasmid containing 12 kilobases of Methylococcus DNA and provide the first evidence for the localization and linkage of genes encoding the methane monooxygenase enzyme complex. DNA sequence analysis suggests that the primary structures of the and subunit of MMO are completely novel and the complete sequence of these genes is presented.     

Die Gattungsmerkmale vonSchizoboea (Gesneriaceae-Didymocarpeae)

The two characters used byBurtt (1974) to segregate the genusSchizoboea fromDidymocarpus, viz. terminal inflorescence and fruit splitting into 4 valves, have been studied in detail: (a) The terminal inflorescence represents a bracteate florescence (sensuTroll), that is an open thyrse, peculiar because of its only two extremely condensed internodes (basic internode + 1 following internode). Correspondingly, there are only two pairs of bracts from which the lower one only is capable to develop axillary partial florescences, i.e. pair-flowered cymes. Thus, the number of cymes is restricted to 2. Because of the condensed internodes, the inconspicuous bracts, and the densely aggregated flowers the two cymes simulate a unitary, terminal structure. By sympodial (± asymmetrically dichasial) linkage of shoot units, composed of an extended internode, a foliage leaf pair (from the axils of which the consecutive units arise) and the florescence,Schizoboea forms (polytelic) anthocladial shoot systems like some genera of the tribeKlugieae (incl.Loxonieae). (b) The fruit dehisces first loculicidally, then each valve splits into three portions (lateral rib and 2 semivalves). Moreover, the 4 placentae become isolated, thus the old fruit comprises 10 elements forming a loose fascicle.—The segregation ofSchizoboea fromDidymocarpus is supported. Whether the affinity is closer toSaintpaulia (as suspected byBurtt) ot toDidymocarpus, remains undecided: In regard to its shoot and inflorescence organization a morphological derivation is possible from both genera.

     

A regional localisation for an X-linked suppressor gene (XS) for the Lutheran blood group

Summary Suppression of Lutheran blood group expression is usually associated with an autosomal dominant suppressor gene In(Lu) which results in the rare Lu(a-b-) phenotype. X-linked recessive suppression can also occur under the control of the XS locus with normal (XS1) and suppressor (XS2) alleles. The only known kindred with XS2 segregating was examined for polymorphic DNA markers with known regional localisations on the X chromosome. Two point linkage analysis suggested linkage of XS to DXS14 (p58.1) with =0.00, =1.96. DXS14 is situated near the centromere at Xp11. Recombinants with DXS84 (distal to DXS14 on Xp) and recombinants with DXYS1 (pDP34) (on the proximal part of Xq) suggests a localisation for XS near the centromere, between DXS84 and DXYS1 (Xp21.2-Xq21.1). Linkage to a marker on the X chromosome confirms the original assignment of XS to the X chromosome, which was based on pedigree inspection from this family.     

Polymorphisms at the GLUT1 (HepG2) and GLUT4 (muscle/adipocyte) glucose transporter genes and non-insulin-dependent diabetes mellitus (NIDDM)

Summary In order to determine the possible contribution of the GLUT1 (HepG2) glucose transporter gene to the inheritance of non-insulin-dependent diabetes mellitus (NIDDM), two restriction fragment length polymorphisms (RFLPs) and the related haplotypes at this locus were studied in 48 Italian diabetic patients and 58 normal subjects. Genotype frequencies for the XbaI polymorphism were significantly different between patients and controls (XbaI: ² = 9.80, df= 2, P < 0.0079). A significant difference was also found in the allele frequencies between NIDDM patients and controls (² =9.39, df = 1, P < 0.0022), whereas no differences were found for the StuI RFLP. No linkage disequilibrium was detected between the XbaI and StuI RFLPs in this sample. The analysis of the four haplotype frequencies (X1S1, X1S2, X2S1, X2S2) revealed a significant difference between diabetic patients and controls (² = 14.26, df =3, P < 0.002). By comparing single haplotype frequencies, a significant difference between the two groups was found for the X1S1 and X2S2 haplotypes. A two-allele RFLP at the GLUT4 (muscle/adipocyte) glucose transporter gene, detected with the restriction enzyme KpnI, was also examined; no differences were found between patients and controls for this RFLP. The finding of an association between polymorphic markers at the GLUT1 transporter and NIDDM suggests that this locus may contribute to the inherited susceptibility to the disease in this Italian population.     

Development and characterisation of 140 new microsatellites in apple (Malus x domestica Borkh.)

The availability of suitable genetic markers is essential to efficiently select and breed apple varieties of high quality and with multiple disease resistances. Microsatellites (simple sequence repeats, SSR) are very useful in this respect since they are codominant, highly polymorphic, abundant and reliably reproducible. Over 140 new SSR markers have been developed in apple and tested on a panel of 7 cultivars and 1 breeding selection. Their high level of polymorphism is expressed with an average of 6.1 alleles per locus and an average heterozygosity (H) of 0.74. Of all SSR markers, 115 have been positioned on a genetic linkage map of the cross Fiesta × Discovery. As a result, all 17 linkage groups, corresponding to the 17 chromosomes of apple, were identified. Each chromosome carries at least two SSR markers, allowing the alignment of any apple molecular marker map both with regard to identification as well as to orientation of the linkage groups. To test the degree of conservation of the SSR flanking regions and the transferability of the SSR markers to other Rosaceae species, 15 primer pairs were tested on a series of Maloideae and Amygdaloideae species. The usefulness of the newly developed microsatellites in genetic mapping is demonstrated by means of the genetic linkage map. The possibility of constructing a global apple linkage map and the impact of such a number of microsatellite markers on gene and QTL mapping is discussed.     

Mapping strategy for resistance genes in tomato based on RFLPs between cultivars: Cf9 (resistance to Cladosporium fulvum) on chromosome 1

Summary The contribution of introgressed regions derived from wild species to the genetic variation within the species of Lycopersicon esculentum was investigated by comparing the RFLP patterns of 2 introgression-free, obsolete cultivars (Moneymaker and Premier) and a modern cultivar (Sonatine) that carries at least 5 introgressed resistance genes. In this analysis 195 mapped nuclear markers were used in combination with 6 restriction enzymes. Among the 1170 probe-enzyme combinations tested, only 3 showed a polymorphism between the 2 introgression-free cultivars. On the other hand 24 probe-enzyme combinations were found to exhibit polymorphisms between Moneymaker and Sonatine. These represented ten polymorphic loci distributed among 5 linkage groups on chromosomes 1, 3, 4, 6, and 9.On the assumption that most of the polymorphic loci corresponded to introgressed chromosome segments of wild species carrying resistance genes, linkages between these loci and the component resistance genes were examined by RFLP analysis of pairs of near-isogenic lines differing only for one particular resistance gene, and a variety of commercial cultivars having different resistance gene compositions. Two of the polymorphic linkage groups could thus be ascribed to resistance genes whose map positions were already known: Cf2 on chromosome 6 and Tm2a on chromosome 9, whereas another marker, TG301 on chromosome 1, could be assigned to the Cladosporium fulvum resistance gene Cf9 with a hitherto disputable map position. By linkage analysis of a segregating F₂ population the genetic distance between the Cf9 gene and the marker TG301 was estimated at 5.5 ± 2.3 cM.     

Characterization of quantitative trait loci (QTLs) in cultivated rice contributing to field resistance to sheath blight (Rhizoctonia solani)

Sheath blight, caused by Rhizoctonia solani, is one of the most important diseases of rice. Despite extensive searches of the rice germ plasm, the major gene(s) which give complete resistance to the fungus have not been identified. However, there is much variation in quantitatively inherited resistance to R. solani, and this type of resistance can offer adequate protection against the pathogen under field conditions. Using 255 F₄ bulked populations from a cross between the susceptible variety Lemont and the resistant variety Teqing, 2 years of field disease evaluation and 113 well-distributed RFLP markers, we identified six quantitative trait loci (QTLs) contributing to resistance to R. solani. These QTLs are located on 6 of the 12 rice chromosomes and collectively explain approximately 60% of the genotypic variation or 47% of the phenotypic variation in the LemontxTeqing cross. One of these resistance QTLs (QSbr4a), which accounted for 6% of the genotypic variation in resistance to R. solani, appeared to be independent of associated morphological traits. The remaining five putative resistance loci (QSbr2a, QSbr3a, QSbr8a, QSbr9a and QSbr12a) all mapped to chromosomal regions also associated with increased plant height, three of which were also associated with QTLs causing later heading. This was consistent with the observation that heading date and plant height accounted for 47% of the genotypic variation in resistance to R. solani in this population. There were also weak associations between resistance to R. solani and leaf width, which were likely due to linkage with a QTL for this trait rather than to a physiological relationship.     

Lectin histochemistry of nephroblastoma (Wilms' tumour)

Summary Paraffin sections of seven cases of nephroblastoma and one case of clear cell sarcoma were stained with a battery of eleven lectins conjugated to horseradish peroxidase. Lectin staining revealed similarities between blastema and stroma with respect to their content of glycoconjugates whereas blastema and epithelial cells exhibited major differences. In general, blastema and stroma contained glycoconjugates with terminal or penultimate -galactose, glycoconjugates having either biantennary or triantennary N-linked sugar chains or both, sialoglycoconjugates, and occasionally glycogen. Epithelial cells also showed these complex carbohydrates but stained additionally for terminal disaccharide galactose-(13)-N-acetylgalactosamine, terminal -galactose and terminal -N-acetylgalactosamine. Furthermore, staining with three fucose-binding lectins revealed that the linkage between terminal -fucose residues to the constituent oligosaccharide chains varied between epithelial cells, blastema and stroma. In general, the distribution and content of glycoconjugates in tumour cells comprising clear cell sarcoma resembled that in blastema and stroma of nephroblastoma. Other findings included differences in content of glycosubstance between cuboidal and columnar cells within the same tumour. Also observed were variations between a primary tumour and its metastasis with respect to the occurrence of certain complex carbohydrates.