Made available in DSpace on 2014-06-11T19:28:30Z (GMT). No. of bitstreams: 0 Previous issue date: 2011-02-28Bitstream added on 2014-06-13T20:37:27Z : No. of bitstreams: 1 souza_a_me_jabo.pdf: 1098095 bytes, checksum: 90c36824f4f63db09ab3ab57ecb91613 (MD5) / Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) / A mangueira (Mangifera indica L.) conta com diversos problemas de ordem fitossanitária, destacando-se como um dos mais importantes, a antracnose, causada na maioria das vezes pelo fungo C. gloeosporioides. Dada a importância comercial dessa doença, esse trabalho teve por objetivo realizar a caracterização genética e patogênica de uma população de isolados de Colletotrichum spp. oriundos de tecidos com sintomas de antracnose de diferentes variedades e órgãos das plantas de manga, dos principais municípios produtores do Estado de São Paulo, além de compará-los geneticamente com isolados obtidos de citros. O sequenciamento da região ITS1-5.8S-ITS2 possibilitou a identificação de 183 isolados de uma população obtida de mangueiras como C. gloeosporioides, com exceção de apenas um deles, o qual foi identificado como C. acutatum. Já os isolados de citros, sendo três obtidos de folhas assintomáticas e dois de flores com sintomas de podridão, foram classificados em C. gloeosporioides e C. acutatum, respectivamente. Os resultados obtidos mediante o emprego de marcadores fAFLP indicaram uma alta variabilidade genética entre isolados de uma mesma população e a ocorrência de fluxo gênico. Além disso, tais resultados corroboraram aqueles obtidos pelo sequenciamento da região ITS1-5.8S-ITS2, por agruparem os isolados do estudo segundo a sua espécie. Os isolados representativos da população, inclusive aqueles obtidos de citros, de ambas as espécies de Colletotrichum, causaram sintomas típicos de antracnose quando inoculados em folhas de mangueiras „Palmer‟ e „Tommy Atkins‟, indicando que, provavelmente, não há especificidade de hospedeiros para essas espécies / The mango crop (Mangifera indica L.) is attacked by several diseases and in this context, the anthracnose is one of the most important. This disease is caused by the fungus C. gloeosporioides in most situations. Due to economic importance of the anthracnose on mango, the aim of this study was to analyze the genetic and pathogenic variability of Colletotrichum spp. isolates obtained from different organs and varieties of mango plants with anthracnose symptoms, and from different municipalities of São Paulo State that are among the major producers of mango. The isolates from mango were also compared with isolates obtained from citrus. Sequencing of ITS1-5.8S-ITS2 region from 183 isolates obtained from mango allowed the identification of them as C. gloeosporioides, however, one of them, was identified as C. acutatum. The isolates from citrus, obtained from syptomless leaves and flowers with rot symptoms, were identified as C. gloeosporioides and C. acutatum, respectively. The results obtained by applying fAFLP markers indicated high level of genetic variability among isolates within population and the occurrence of gene flow. Moreover, these results corroborated those achieved by sequencing of the ITS1-5.8S-ITS2 region, because the isolates were grouped according to its species. Representative isolates of the population, including those obtained from citrus, belonging to both species of Colletotrichum, caused typical symptoms of anthracnose disease on mango leaves of Palmer and Tommy Atkins varieties, indicating the lack of host specificity for these species

Flesh colour and fillet fat percentage are the two most important attributes to salmon fillet quality. A medium genetic component to body lipid percentage within commercial lines has previously been shown (h2 = 0.17-0.24). A low level of heritability (h2 = 0.16) has also been reported for flesh colour in Atlantic salmon. To investigate whether this genetic component includes loci of major effect, a genome-wide QTL scan was performed with commercially bred Atlantic salmon (Landcatch Natural Selection). Five large full-sib families (10 parents with 153 offspring) were genotyped using microsatellite markers. To utilize the large difference between sire and dam recombination rate, a two-stage genotyping was employed. Initially, the parents and offspring were genotyped for two microsatellite markers per linkage group, and sire based QTL analysis was used to detect linkage groups with significant effects on those flesh quality traits. A linear-regression based interval as analytical method was applied for QTL detection. The results revealed evidence of QTLs affecting percentage fat percentage and flesh colour on linkage groups LNS16 and LNS1 respectively. To confirm the QTL and to provide an improved estimate of position, a dam-based analysis was then employed. One major QTL was located on the genome-wide significance level for percentage fat percentage. Microsatellite marker Ssa0016NVH (at position of 1.3 cM) was found to be tightly linked to QTL affecting percentage fat percentage. In addition, a QTL affecting flesh colour was found to be flanked by microsatellite markers Ssa9.44NUIG at position of 68.7 cM and Ssa0021NVH at position of 50.6 on linkage group LNS16. The evidence for suggestive QTL affecting flesh colour on linkage group LNS1 was also revealed. In order to increase marker density within these and other linkage groups, AFLP markers were employed, 24 primer combinations resulted in a total of 489 polymorphic fragments. Among 11 fragments that were found to be linked to the microsatellite markers on linkage group LNS16, four fragments (AAG-CAC328, AGG-CAG447, AGG-CTA237 and AGG-CTC237) were tightly linked to microsatellite marker Ssa9.44NUIG, but none were found to be linked to microsatellite Ssa0021NVH. Moreover, none of the AFLP markers were found to be linked to microsatellites residing on linkage group LNS1. Using a constructed map of microsatellite and AFLP markers for linkage group LNS16, the dam based analysis revealed a significant QTL for flesh colour at the location of 189 cM, while the sire based analysis detected a significant QTL for fat percentage at the location of 80 cM. Considering the dominant nature and clustering character of AFLP markers, it was concluded that a certain primer combination in AFLP markers could be of limited use for fine mapping and QTL detection in Atlantic salmon.

The co-occurrence of polyploidy and clonal reproduction among plant species has long been recognized, but the evolutionary mechanisms underlying the association are unknown. Here, I investigate whether polyploidy increases the magnitude of clonality, either directly or indirectly, by comparing the extent and spatial structure of clones between diploid and tetraploid Chamerion angustifolium in a greenhouse environment and natural populations. In the greenhouse, tetraploid plants allocated 90.4% more dry mass to root buds, the primary mechanism of clonal reproduction, than diploids. Per unit root mass, tetraploids produced 44% fewer root buds and the average position of the root buds along the root was 47% closer to the stem than in diploids. In natural populations, the magnitude of clonality in tetraploid C. angustifolium was similar or less than in diploids. However, clones were spatially aggregated in all diploid populations but only in two of five tetraploid populations. Average clone patch diameter, however, was not significantly different between diploids (3.9 m) and tetraploids (2.5 m). These data do not support the hypothesis that clonality increases as a result of genome duplication. Rather, it is possible that clonality is linked to genome duplication because clonal diploids are predisposed for polyploid formation and establishment. / National Science and Engineering Research Council, Canada Research Chair Program, Canadian Foundation for Innovation

Knowledge of the genetic variation of crop collections is essential for their efficient use in plant breeding programs. The Ethiopian Highland Maize Germplasm Collection Mission was launched throughout the highlands of Ethiopia in 1998 and 287 traditional maize accessions were collected from farmers’ fields. To date, no information was available on the morphological and genetic diversity in this important collection. Various molecular marker techniques and quantitative genetics approaches were applied to accurately unravel the extent of phenotypic and genetic diversity, to study patterns of morphological and molecular variation and to determine association of molecular markers with quantitative trait variation, with the view of designing a sound breeding program and management strategy for maize in the highlands of Ethiopia. The morphological study confirmed that traditional Ethiopian highland maize accessions contain large amounts of variation for agro-morphological traits. The broad trait diversity observed among the accessions suggested ample opportunities for the genetic improvement of the crop through selection directly from the accessions and/ or the development of inbred lines for a future hybrid program. Selection practices followed by local farmers are mostly consistent within agroecology and gave rise to morphologically distinct maize accessions in different agroecologies. This underscores the importance of considering farmers’ knowledge of diversity in the collection and evaluation of local accessions. The results of amplified fragment length polymorphism (AFLP) and microsatellite or simple sequence repeat (SSR) marker analyses showed that bulking leaf samples from 15 individual plants per out-bred accession is an effective means of producing representative profiles of individual plants, thereby reducing the cost of DNA extraction and subsequent marker analysis of open-pollinated varieties. Cluster analyses based on AFLP and SSR data showed that most of the accessions collected from the Northern agroecology were genetically distinct from the Western and Southern accessions suggesting that differentiation for adaptive traits for drought conditions may have occurred in the Northern accessions. However, there was very little genetic differentiation between the Western and Southern accessions suggesting gene flow between the two agroecologies and recent introduction of similar improved varieties in these agroecoogies . In both marker systems, high mean genetic diversity was observed among the traditional Ethiopian highland maize accessions. This is possibly due to (i) the continuous introduction of maize from abroad by different organizations; (ii) genetic variation generated through farmers management practices; and (iii) the presence of different environmental conditions in the highlands of Ethiopia to which local landraces may have been adapted. The correlation between the morphological dissimilarity matrix and the matrices of genetic dissimilarity based on SSR and AFLP markers were 0.43 and 0.39, respectively (p = 0.001 in both cases). The correlation between SSR and AFLP dissimilarity matrices was 0.67 (p = 0.001). These significant correlations indicate that the three independent sets of data likely reflect the same pattern of genetic diversity, and validate the use of the data to calculate the different diversity statistics for Ethiopian highland maize accessions. From this study, three groups of maize accessions with distinctive genetic profiles and morphological traits were identified that will be useful for future collection, conservation and breeding programs of maize for the highlands of Ethiopia. A pilot association study using SSR markers and quantitative trait variation indicated that molecular markers could be useful to identify genetic factors controlling earliness, tallness, grain yield and associated traits, which could be exploited by various breeding schemes. The analytical tools outlined in this dissertation can be a useful tool in managing genetic variation of open-pollinated crops and will aid in the conservation of unique genetic diversity. Production stability and global food security are linked to the conservation and exploitation of worldwide genetic resources and this research attempts to add to that body of knowledge. Copyright 2005, University of Pretoria. All rights reserved. The copyright in this work vests in the University of Pretoria. No part of this work may be reproduced or transmitted in any form or by any means, without the prior written permission of the University of Pretoria. Please cite as follows: Beyene, YA 2005, Genetic analysis of traditional Ethiopian Highland Maize (Zea Mays l.) using molecular markers and morphological traits : implication for breeding and conservation, PhD thesis, University of Pretoria, Pretoria, viewed yymmdd < http://upetd.up.ac.za/thesis/available/etd-02212006-112610 / > / Thesis (PhD (Genetics))--University of Pretoria, 2005. / Genetics / unrestricted