No description available.

No description available.

<p>&nbsp / </p> <p align="left">The domesticated apple (<i><font face="TimesNewRomanPS-ItalicMT">Malus </font><font face="TimesNewRomanPSMT">x </font><i><font face="TimesNewRomanPS-ItalicMT">domestica </font><font face="TimesNewRomanPSMT">Borkh.), belonging to the </font><i><font face="TimesNewRomanPS-ItalicMT">Malus </font><font face="TimesNewRomanPSMT">genus of the Rosaceae family, is one of the edible pomaceous fruits. Since it is one of the important commercial fruit crops worldwide, the quality of the fruit is crucial to breeders and farmers as it ultimately determines acceptance of a cultivar for consumption. Fruit quality is also a critical determinant factor that is used to estimate the potential of apples to have a long shelf life. The introduction of marker-assisted selection (MAS) has allowed hastening of traditional breeding and selection of high-quality apple cultivars. The availability of genetic linkage maps, constructed by positioning molecular markers throughout the apple genome, enables the detection and analysis of major genes and quantitative trait loci (QTLs) contributing to the quality traits of a given genotype.&nbsp / herefore, the primary aim of this study was to construct a genetic linkage map of the &lsquo / Golden Delicious&rsquo / x &lsquo / Dietrich&rsquo / population for the identification of QTLs associated with fruit quality traits and then to examine the apple fruit pulp proteome with a specific focus on fruit firmness. In this regard, genomic DNA was extracted from leaves of the &lsquo / Golden Delicious&rsquo / x Dietrich&rsquo / population and used in megaplex PCR reactions. The PCR products were analysed prior to scoring of alleles. Polymorphic markers were then used to construct genetic linkage maps. The genetic linkage maps constructed in this study comprise of 167 simple sequence repeats (SSR) markers, 33 of these were newly developed markers. The 17 linkage groups of apple were constructed and aligned to existing apple genetic maps. The maps span 1,437.8 cM and 1,491.5 cM for &lsquo / Golden Delicious&rsquo / and &lsquo / Dietrich&rsquo / , respectively.</font></i></i></i></p>

The independent evolution of the sexes may often be constrained if male and female homologous traits share a similar genetic architecture. Thus, cross-sex genetic covariance is assumed to play a key role in the evolution of sexual dimorphism (SD) with consequent impacts on sexual selection, population dynamics and the speciation process. I used quantitative genetics tools to assess the importance of sex-specific genetic variance in facilitating the evolution of body mass and horn size SD in wild bighorn sheep from Ram Mountain, Alberta. I also developed a bighorn sheep genetic linkage map composed of 247 microsatellite markers to gain insights about the genetic architecture of trait variation. Finally, I conducted systematic reviews and meta-analyses of published cross-sex genetic correlations (rMF, a standardized estimate of cross-sex genetic covariance) to test basic hypotheses about the importance of sex-specific genetic variance in the evolution of SD and mechanisms responsible for generating such variance. My results demonstrated that sex-specific genetic variance was present in bighorn sheep and that it likely played an important role in alleviating intralocus sexual conflicts. The quantitative trait locus (QTL) mapping analysis resulted in the identification of numerous loci influencing body mass and horn dimensions, some of which had apparent sex-specific effects. An analysis of 553 rMF estimates recovered from 114 published sources allowed demonstrating that 1) the evolution of SD was generally constrained by positive cross-sex genetic covariance, 2) levels of SD were often sub-optimal, and 3) sex-specific genetic variance was an important mechanism allowing the evolution of SD. In addition, I confirmed the long-standing hypothesis of a general decline in rMF with age. Sexual dimorphism is an important evolutionary phenomenon, but our understanding of its evolution is still limited. After decades of speculation, my research has provided clear empirical evidence for the importance of sex-specific genetic variance in allowing its evolution. / Ecology

Thesis (Ph. D.)--University of Tennessee, Memphis, 2006. / The electronic version of this thesis is available at http://d.utmem.edu/CAMPUS-ACCESS-ONLY/2006-001-chona.pdf Includes bibliographical references (leaves 128-136).

Thesis (Ph.D.)--University of Alabama at Birmingham, 2009. / Title from PDF title page (viewed on July 13, 2010). Includes bibliographical references.

Doctor of Philosophy / Department of Agronomy / S.V. Krishna Jagadish / Sorghum (Sorghum bicolor (L.) Moench) is one of the hardiest crop to abiotic stresses compared with other grain crops. However early stage chilling, terminal heat and drought stress are three most damaging abiotic stresses that have limited sorghum productivity in the US Great plains and other locations having similar environmental conditions. Three studies were conducted with an overall goal aimed at increasing grain sorghum’s resilience to harsh climatic conditions. In the first study, four promising chilling stress tolerant sorghum advanced breeding lines, a known early stage chilling tolerant Chinese landrace (Shan Qui Red - SQR) and a susceptible US elite cultivar (RTx430) as checks were assessed for chilling tolerance during emergence and early growth under field and controlled environments. Aerial phenotyping using unmanned aircraft systems (UAS) fitted with multispectral camera was used to capture reflectance-based vegetation indices (NDVI and NDRE) in field experiments. Some advanced breeding lines with superior agronomic background also recorded significantly better emergence, seedling growth and vigor compared to SQR under chilling conditions. Aerial phenotyping indices from images taken between 30 and 60 days after emergence were consistently correlated with destructive measurements under early plantings, indicating their effectiveness in differentiating chilling responses. Second study was conducted to understand physiological mechanisms inducing heat stress resilience in sorghum during flowering. A diverse set of sorghum inbreds and selected hybrids were tested under greenhouse, growth chamber facilities and field conditions. A highly conserved early-morning-flowering mechanism was observed across all the inbreds and hybrids, with the peak anthesis wherein >90% of florets completed flowering within 30 min after dawn. The conserved response was consistent even under drought stress and heat stress exposure imposed at different times of the day. Our findings report a novel heat escaping early-morning-flowering mechanism effectively employed by sorghum to minimize heat stress impact at anthesis. Another experiment with sequential increase in daytime temperature treatments suggest heat stress induced loss in pollen viability to be a key factor resulting in reduced seed-set and grain yield. The findings suggest heat stress could have a greater impact on post-pollen germination processes such as fertilization, embryo formation and development. We identified a heat tolerant genotype “Macia” which appears to be a promising donor for developing improved heat tolerant sorghum hybrids. In the third study, a bi-parental recombinant inbred lines (RILs) mapping population developed from elite post flowering drought susceptible cultivar (RTx430) and a known drought tolerant cultivar (SC35) were evaluated under wide spectrum of environments and moisture conditions. Several novel and major QTL for grain yield, panicle neck diameter, effective quantum yield of photosystem II and chlorophyll content were identified. The genomic regions and the candidate genes within these regions can potentially help in improving source and sink dynamics in sorghum under diverse environments. The findings from these studies will complement ongoing efforts in developing future sorghum with enhanced resilience to different abiotic stresses that continue to limit sorghum productivity.

Genetic associations have been discovered for many human complex traits, and yet for most associated loci the causal variants and molecular mechanisms remain unknown. Studies mapping quantitative trait loci (QTLs) for molecular phenotypes, such as gene expression, RNA splicing, and chromatin accessibility, provide rich data that can link variant effects in specific cell types with complex traits. These genetic effects can also now be modeled in vitro by differentiating human induced pluripotent stem cells (iPSCs) into specific cell types, including inaccessible cell types such as those of the brain. In this thesis, I explore a range of approaches for using QTLs to identify causal variants and to link these with molecular functions and complex traits. In Chapter 2, I describe QTL mapping in 123 sensory neuronal cell lines differentiated from human iPSCs. I observed that gene expression was highly variable across iPSC-derived neuronal cultures in specific gene categories, and that a portion of this variability was explained by commonly used iPSC culture conditions, which influenced differentiation efficiency. A number of QTLs overlapped with common disease associations; however, using simulations I showed that identifying causal regulatory variants with a recall-by- genotype approach in iPSC-derived neurons is likely to require large sample sizes, even for variants with moderately large effect sizes. In Chapter 3, I developed a computational model that uses publicly available gene expression QTL data, along with molecular annotations, to generate cell type-specific probability of regulatory function (PRF) scores for each variant. I found that predictive power was improved when the model was modified to use the quantitative value of annotations. PRF scores outperformed other genome-wide scores, including CADD and GWAVA, in identifying likely causal eQTL variants. In Chapter 4, I used PRF scores to identify relevant cell types and to fine map potential causal variants using summary association statistics in six complex traits. By examining individual loci in detail, I showed how the enrichments contributing to a high PRF score are transparent, which can help to distinguish plausible causal variant predictions from model misspecification.

No description available.

Philosophiae Doctor - PhD / The domesticated apple (Malus x domestica Borkh), belonging to the Malusgenus of the Rosaceae family, is one of the edible pomaceous fruits. Since it is one of the important commercial fruit crops worldwide, the quality of the fruit is crucial to breeders and farmers as it ultimately determines acceptance of a cultivar for consumption. Fruit quality is also a critical determinant factor that is used to estimate the potential of apples to have a long shelf life / South Africa