Browsing by Author "Cabrita, L."
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- Assessment of genetic relationships among Pyrus species and cultivars using AFLP and RAPD markersPublication . Monte-Corvo, L.; Cabrita, L.; Oliveira, C.; Leitão, J. M.Twenty-five Pyrus communis L. cultivars including eight traditional Portuguese pears, and four commercial Pyrus pyrifolia (Burm.) Nak. (Japanese pear or 'nashi') cultivars were analysed by RAPD and AFLP techniques focusing on their molecular discrimination and the assessment of their genetic relatedness. Twenty-five primers generated 324 RAPD markers, among which 271 (84%) were polymorphic. The AFLP technique, using seven primer combinations, revealed a similar level of molecular polymorphisms (87%), representing 418 polymorphic bands among a total of 478 scored in autoradiographs. The high reproducibility of RAPD and AFLP techniques was confirmed comparing DNA samples from different extractions and different digestions of DNA from the same plant. Three genetic similarity matrices and respective dendrograms were elaborated on using RAPD, AFLP or joint RAPD and AFLP data. Both molecular marker techniques proved their reliability to assess genetic relationships among pear cultivars. P. pyrifolia cultivars exhibit a closer genetic relatedness, clustering apart from P. communis cultivars. Within P. communis, 'William's', as well as 'Doyenne du Comice', cluster close to their hybrids. Most of the Portuguese cultivars tend to cluster together, indicating to constitute a relatively independent genetic pool, which can be of interest in pear breeding programs.
- Comparing RAPD and AFLP (TM) analysis in discrimination and estimation of genetic similarities among apple (Malus domestica Borkh.) cultivars - RAPD and AFLP analysis of applesPublication . 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 = 73.7%) between the analysis with the two different markers. UPGMA analysis was performed and dendrograms were constructed using either the data apart from each (RAPD and AFLP) method or combined in a single joint matrix. The relationships among the forty-one studied cultivars were basically consistent with the known lineage and geographic origins of the cultivars. The four Portuguese cultivars included in this study clustered together and diverged from the other cultivars. Apparently they constitute an independent genetic pool, which could be of interest for apple plant breeders.
- Evaluation of resistance to Phomopsis amygdali in almondPublication . Cabrita, L.; Neves, A.; Leitão, JoséThe 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). The 'Barrinho Grado' progeny showed higher resistance to the disease than the population descended from 'Ferragnes'. In order to study the inheritance of resistance to this fungus several controlled crosses were performed involving susceptible and resistant cultivars and the respective progeny plants were inoculated with fungus isolates in order to ascertain their phenotype. Moreover, to evaluate genetic variability of parents involved in the crosses, preliminary studies using isozymes, microsatellites, RAPD and ISSR markers were performed. Genetic similarities between these cultivars were established and suitable molecular markers for genomic mapping were selected. Hybrid populations will be used to construct genetic maps and to identify molecular markers closely linked to the resistance gene(s).
- Genetic diversity assessment of the almond (Prunus dulcis (Mill.) DA Webb) traditional germplasm of Algarve, Portugal, using molecular markersPublication . Cabrita, L.; Apostolova, E.; Neves, Alcinda; Marreiros, A.; Leitão, JoséIn 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 the analysed trees among 140 discriminating DNA patterns. Multiple cases of homonymy and synonymy were identified in the local germplasm. Some traditional varieties, such as Lourencinha, appeared to be relatively homogeneous, while other local denominations, e.g. Galamba, included diverse genotypes. Of the 13 commercial varieties analysed in this study, 11 assembled in one major cluster clearly differentiated from the majority of the local genotypes. These results reinforced the perception that the Algarve traditional germplasm constitutes an important repository of genetic diversity, eventually carrying alleles of high agricultural interest such as the recently identified Phomopsis resistance in the traditional variety Barrinho Grado.
- ISSR and AFLP characterization of Phomopsis amygdali ((Del.) Tuset & Portilla AccessionsPublication . Carlier, Jorge; Cabrita, L.; Leitão, José; Sousa, R. M.; Sousa, A. T.The fungus Phomopsis amygdali (Del.) Tuset & Portilla (sin: Fusicoccum amygdali Delacr.) is one of the most important almond (Prunus dulcis (Mill.) Webb) diseases in Portugal, causing cankers on one-year-old branches, and wilting and death of infected twigs and shoots. The disease leads frequently to tree decline and death. In the Algarve region of Portugal, the most common commercial cultivars show severe damages while some traditional almond cultivars seem not to be significantly affected. Infected plant material was collected from almond and peach trees. Fungi present in the infected tissues were isolated on PDA medium and transferred to the mycotec managed by the Estacao Nacional de Fruticultura Vieira Natividade (ENFVN). Some fungi accessions were identified as Eutypa lata (Pers.: Fr.) Tul. & C. Tul. Seventeen accessions, one identified as Eutypa and sixteen as Phomopsis, were analyzed by ISSR and AFLP techniques. Fourteen Phomospsis accessions, grouped in a main cluster, showed a coefficient of similarity (DICE) over 0.88. One of the putative Phomopsis accessions showed to be erroneously classified as it displays strong genetic similarity (DICE 0.92) to the Eutypa accession, while these two samples presented very low genetic similarity (DICE 0.20) to the main group of Phomopsis accessions. One sample, which we hypothesize to be of Cytospora sp. remained apart (DICE 0.15) from all the other accessions. The identification and cloning of molecular markers specific to each pathogenic species will be of major interest for further rapid identification of the causal agent of canker symptoms in almond.
- Molecular characterization of Phaseolus vulgaris L. genotypes included in Bulgarian collection by ISSR and AFLP (TM) analysesPublication . Svetleva, D.; Pereira, G.; Carlier, Jorge; Cabrita, L.; Leitão, J. M.; Genchev, D.Seventy-eight (33 Bulgarian and 45 foreign) common bean (Phaseolus vulgaris L.) genotypes included in Bulgarian collection were screened for ISSR (Inter Simple Sequence Repeats) and AFLP (TM) (Amplified Fragment Length Polymorphism) markers. ISSR analysis was performed with 13 primers, and 55 (36.7%) out of the 150 bands observed were polymorphic. One hundred and sixty-four AFLP (TM) fragments were obtained with three primer combinations, of which 54 (32.9%) were polymorphic. UPGMA (Unweighted Pair Group Method Arithmetic Averages) analysis was performed using DICE coefficient and dendrograms were constructed using either the data from each method (ISSR and AFLP (TM)) separately or combined in a single joint matrix. Despite some genetic heterogeneity observed in both pools (Middle American origin: M and Andean origin: A) the genotypes were separated in to main groups: one gathering genotypes mainly from pool M and the other more genotypes from pool A. Moreover, Bulgarian genotypes were spread over the two groups suggesting that they are not subject to genetic erosion and that the Phaseolus genetic diversity is conserved. (c) 2006 Elsevier B.V. All rights reserved.