Mostrando recursos 1 - 20 de 55

  1. Correction of the misclassification of species in the Portuguese collection of Cucurbita pepo L. using DNA markers

    Rodrigues, R.; Veiga, I.; Marreiros, A.; Rocha, F.; Leitão, J. M.
    In this study, the genetic variability among 130 accessions of the Portuguese germplasm collection of Cucurbita pepo L. maintained at the Banco Portugues de Germoplasma Vegetal was assessed using AFLP (amplified fragment length polymorphism) and RAPD (random amplified polymorphic DNA) techniques for the identification of a genetically diverse core group of accessions for field phenotypic analysis. The surprisingly completely different molecular patterns exhibited by multiple accessions was later confirmed in the distribution of the putative C. pepo plants into two clusters drastically separated at a very low level of genetic similarity (DICE coefficient = 0.37). Additional analyses with RAPD and...

  2. A genetic map of pineapple (Ananas comosus (L.) Merr.) including SCAR, CAPS, SSR and EST-SSR markers

    Carlier, JD; Sousa, NH; Santo, TE; d'Eeckenbrugge, GC; Leitao, JM
    Despite the paramount importance of pineapple (Ananas comosus L.) in world production and trade of tropical fruits, the genomics of this crop is still lagging behind that of other tropical fruit crops such as banana or papaya. A genetic map of pineapple was constructed using an F2 segregating population obtained from a single selfed F1 plant of a cross A. comosus var. comosus (cv. Rondon, clone BR 50) x A. comosus var. bracteatus (Branco do mato, clone BR 20). Multiple randomly amplified markers (RAPD, ISSR and AFLP) were brought together with SSR and EST-SSR markers identified among sequences uploaded to...

  3. Assessment of the genetic relationships among citrus species and varieties by isozyme and RAPD markers

    Cabrita, L; Elisiario, P; Leitao, J; Guerreiro, A
    A group of 22 Citrus varieties (sweet oranges, lemons, grapefruits, clementines and several other mandarin biotypes) was analysed by isozyme and RAPD markers in order to assess their genetic relationships. Four isozyme systems (GOT, IDH, PGM and PGI) revealed seven loci, four of them polymorphic. Sweet oranges, lemons, grapefruits and clementines were discriminated at the species level but individual varieties within each species remained undistinguishable by the analysed isozyme systems. Nevertheless, a specific isozyme pattern was found for almost each one of the mandarin varieties with the exception of Carvalhais and Fremont, which shared an identical isozyme pattern. Additionally, RAPD...

  4. Genetic diversity assessment of the almond (Prunus dulcis (Mill.) DA Webb) traditional germplasm of Algarve, Portugal, using molecular markers

    Cabrita, L.; Apostolova, E.; Neves, Alcinda; Marreiros, A.; Leitao, J. M.
    In this study, 123 almond (Prunus dulcis (Mill.) D. A. Webb) trees identified among traditional orchards in the Algarve region and 53 trees of the local field collection managed by the regional office of the Portuguese Ministry of Agriculture (DRAALG) were assessed using isozyme, inter- single sequence repeat and simple sequence repeat or microsatellite techniques for the evaluation of genetic diversity and genetic relatedness and identification of new accessions for the field collection. The isozyme analysis allowed the distribution of the 176 plants into 13 different classes of enzyme similarity, while the use of DNA markers increased the distribution of...

  5. The downy mildew resistance locus Pp523 is located on chromosome C8 of Brassica oleracea L.

    Carlier, J. D.; Alabaca, C. A.; Coelho, P. S.; Monteiro, A. A.; Leitão, J. M.
    We have previously constructed a genetic map of Brassica oleracea L. containing the Pp523 locus that confers downy mildew resistance to adult plants. In this work, 44 SSR markers of reference for the Brassica C genome chromosomes were added to the map, allowing the nine major linkage groups to be assigned to the nine chromosomes of B. oleracea. Locus Pp523 was located on chromosome C8, and a locus determining flower colour was mapped to chromosome C3. In comparison with the first version of the map, the new map is denser and more compact. The available genomic information on B. oleracea...

  6. Comparing RAPD and AFLP (TM) analysis in discrimination and estimation of genetic similarities among apple (Malus domestica Borkh.) cultivars - RAPD and AFLP analysis of apples

    Goulão, L.; Cabrita, L.; Oliveira, C.; Leitão, J. M.
    Forty-one apple ( Malus x domestica Borkh.) cultivars were screened for RAPD (Random Amplified Polymorphic DNA) and AFLP (Amplified Fragment Length Polymorphism) markers. RAPD analysis was performed with 35 arbitrary 10-mer primers, selected from 60 primers tested (kits A, C and E, Operon Technologies, Inc.). Of a total of 362 bands observed, 208 (57.5%) were polymorphic. Three-hundred-and-eighty-one AFLP fragments were obtained with 8 primer combinations, of which 218 (57.2%) were polymorphic. Cultivars differentiated through mutation were included in this study and showed identical patterns when analysed with both RAPD and AFLP analysis. The estimated genetic relationships were correlated (r =...

  7. The induction of DNA strand breaks at specific sites by N-nitroso-N-ethylurea depends on the phases of the cell cycle

    Leitao, J; Petkova, S; Djondjurov, L

  8. On the Way to the Identification of a Downy Mildew Resistance Gene in Brassica oleracea L.

    Carlier, J; Alabaca, C; Rodrigues, C; Leitao, J
    We have recently mapped the dominant and monogenically inherited downy mildew resistance locus Pp523 to the chromosome C8 of Brassica oleracea L. and constructed a physical-map of the genomic region of this locus. Presently, we are constructing a BAC genomic library of a downy mildew resistant S4 line derived from the broccoli accession originally found to harbor the Pp523 locus and using STS markers derived from the previously constructed physical map in order to identify a contig of BAC clones which sequencing could allow the isolation and cloning of this resistance locus. The new BAC library contains 17280 clones with...


    LEITAO, JM; Lorenz, B; BACHINSKI, N; WILHELM, C; Muller, WEG; Schroder, HC
    The potential role of inorganic polyphosphates in the response of algal cells to osmotic stress was investigated. We show that changes in polyphosphate metabolism of algae induced by osmotic stress can be easily determined by measuring the metachromatic shift of toluidine blue produced by polyphosphate and by analysing the size of the extracted polyphosphate on urea/polyacrylamide gels. The amount and size of polyphosphate were found to differ considerably among different algal species. It is demonstrated that the alga Phaeodactylum tricornutum responds to hyperosmotic stress with a marked elongation of polyphosphate molecules and a decrease in the total amount of extractable...

  10. Suitability of isozyme, RAPD and AFLP markers to assess genetic differences and relatedness among fig (Ficus carica L.) clones

    Cabrita, LF; Aksoy, U; Hepaksoy, S; Leitao, JM
    Sarilop is the main and standard cultivar for commercial dried fig (Ficus carica L.) production in Turkey. Eleven of the most promising Sarilop clones and one clone of Sarizeybek, all selected from a former agronomic evaluation, were analysed by three molecular marker techniques, isozymes, RAPDs and AFLPs. The resolution power and the accuracy of these three analytical techniques, in distinguishing among fig clones, were determined. The analysis of five isozyme systems permitted the discrimination between the two cultivars, Sarilop and Sarizeybek. Besides the discrimination between the two fig cultivars, the use of 31 10-mer primers in RAPD analysis allowed splitting...

  11. Purification and characterization of a pore-forming protein from the marine sponge Tethya lyncurium

    Mangel, A; Leitao, JM; Batel, R; Zimmermann, H; Muller, WEG; Schroder, HC
    A pore-forming protein was detected and purified for the first time from a marine sponge (Tethya lyncurium). The purified protein has a polypeptide molecular mass of 21 kDa and a pI of 6.4. Tethya pore-forming protein (also called Tethya hemolysin) rapidly lysed erythrocytes from a variety of organisms. After binding to target membranes, the hemolysin resisted elution with EDTA, salt or solutions of low ionic strength and hence resembled an integral membrane protein. Erythrocytes could be protected from hemolysis induced by Tethya hemolysin by addition of 30 mM dextran 4 (4-6 kDa; equivalent hydrodynamic diffusion radius, 1.75-2.3 nm) to the...

  12. An integrated genetic map of pineapple (Ananas comosus (L.) Merr.)

    de Sousa, N; Carlier, JD; Santo, T; Leitao, J
    The inclusion of multiple new markers, in particular 41 sequence specific markers, resulted in drastically improved version of a previously published F1-based genetic map of pineapple (Ananas comosus). The integration of the new version of this map with a more recently published F2-based map resulted in a map that assembles 741 loci: 739 DNA markers (25 SSR, 12 EST_SSR, 22 SCAR, 8 CAPS, 20 ISSR, 109 RAPD, and 543 AFLP), one isozyme (PGM) locus and the morphological trait 'piping', in 28 integrated linkage groups, spanning 2113 centimorgans (cM) and covering approximately 86% of the genome. Four small F1-based linkage groups...

  13. Purification and characterization of a D-glucosamine and D-galactosamine specific lectin from Pancratium maritimum L.

    Gago, MF; Schroder, HC; Muller, WEG; Leitao, JM

  14. AFLP, ISSR and RAPD markers reveal high levels of genetic diversity among Lupinus spp.

    Talhinhas, P; Neves Martins, J; Leitao, J
    The Lupinus genus includes a number of important crop species. The use of defined nucleotide sequences for the analysis of genetic diversity among these species has revealed modest levels of diversity. The aim of this study was to access AFLP, ISSR and RAPD markers to evaluate the genetic diversity among L. albus, L. angustifolius, L. cosentinii, L. hispanicus, L. luteus, L. mutabilis, L. pilosus and L. polyphyllus. Unexpectedly, low levels of genetic similarity were found (ranging from 0.205 to 0.432), regardless of the type of molecular marker used. Nevertheless, these techniques consistently showed a greater genetic similarity between L. pilosus...

  15. Role of codon 160 in the sensitivity of human O6-alkylguanine-DNA alkyltransferase to O6-benzylguanine

    Xu Welliver, M; Leitao, J; Kanugula, S; Meehan, WJ; Pegg, AE
    O6-Alkylguanine-DNA alkyltransferase (AGT) is a DNA repair protein that provides protection from alkylating agents such as dacarbazine, temozolomide, and 1,3-bis-(2-chloroethyl)-1-nitrosourea (BCNU), which are used for cancer chemotherapy. O6-Benzylguanine (BG) is an inhibitor of AGT that sensitizes tumors to these agents. BG is currently in clinical trials. It is possible that the presence of resistant forms of AGT may limit the effectiveness of this strategy. Previous studies have shown that the AGT mutant G160R, which may occur naturally as a result of a polymorphism in the AGT gene, is resistant to BG, whereas the mutants G160W and G160A are actually more...

  16. The ENU-induced powdery mildew resistant mutant pea (Pisum sativum L.) lines S(er1mut1) and F(er1mut2) harbour early stop codons in the PsMLO1 gene

    Santo, T; Rashkova, M; Alabaca, C; Leitao, J
    Two pea (Pisum sativum L.) powdery mildew-resistant mutant lines, S(er1mut1) and F(er1mut2), were previously obtained by experimental chemical mutagenesis with ethylnitrosourea. Identification and subsequent analysis of the genomic sequence of the PsMLO1 gene revealed one single nucleotide mutation in each mutant line that leads to either a transversion or a transition, respectively, resulting in premature stop codons that drastically truncate the protein product of this gene in these two mutant lines. These results confirm the previous findings that PsMLO1 is the powdery mildew resistance gene er1. Only one additional mutation (transition) was observed in the S(er1mut1), downstream of the protein-truncating...

  17. A novel method for determination of inorganic polyphosphates using the fluorescent dye fura-2

    Lorenz, B; Munkner, J; Oliveira, MP; Leitao, JM; Muller, WEG; Schroder, HC
    A method for determining inorganic polyphosphate, which is based on the Mn2+-induced quenching of the fluorescence of the calcium indicator fura-2, is described. The effect of Mn2+ ions on fura-2 fluorescence is gradually abolished in the presence of increasing concentrations of polyphosphate; this allows the quantification both of synthetic polyphosphates and of the naturally occurring polymer isolated from tissues or cells. The described method has some advantages compared to conventional procedures for detection of polyphosphates based on the metachromatic effect on toluidine blue. It can be applied for the determination of pyrophosphate, tripolyphosphate and other short-chain polyphosphates not detectable by...

  18. Evaluation of resistance to Phomopsis amygdali in almond

    Cabrita, L; Neves, A; Leitao, J
    The disease caused by the fungus Phomopsis amygdali (Del.) Tuset & Portilla is, today, one of the most important in almond growing, since the main commercial cultivars are susceptible to this pathogen. In Algarve (Portugal), the disease has been causing severe damage to introduced foreign commercial cultivars while traditional cultivars are not significantly affected. Field observations have led to the identification of 'Barrinho Grado' as a local cultivar that has shown non-susceptible behaviour in a heavily infected orchard. Inoculation tests with Phomopsis amygdali isolates were performed on young trees obtained from open-pollinated seeds of 'Barrinho Grado' (resistant) and 'Ferragnes' (susceptible)....

  19. Proceedings of the Third International Symposium on Fig: Foreword

    Leitao, J

  20. Genetic mapping of DNA markers in pineapple

    Carlier, JD; Nancheva, D; Leitao, JM; d'Eeckenbrugge, GC
    Two genetic maps of DNA-markers (RAPD, AFLP and ISSR) of Ananas comosus var. bracteatus and A. comosus var. comosus have been previously published by our team. These maps were constructed at the Laboratory of Genetics and Plant Breeding of FERN, University of Algarve, using an F1 mapping population derived from a cross performed in Martinique between the two botanical varieties. However, the use of a F1 population, the small size of this population and the use of molecular markers with dominant inheritance allowed only markers that were heterozygous in the parents to be included in those maps and prevented the...

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