Mosaic has peculiar status in art across thousands of years. Since antiquility when mosaic governed entire Mediterranean, it stood to be an active art expression till nowadays, even despite it's demandigness and costingness - not only abroad but also at our territory. So it went through the period of decrement and "degradation" of it's own technique due to increasing favour of painting in the Renaissance and lived to see it's follow-up boom in 19th century. The thesis marks geografical expansion inlay art from it's roots till the modern age and it's influence on the technique developement. Historical part is more extensive because it has not been documented more detailed so far, which it definately is worthy to be. Thanks to Viktor Foester, the inlay art was reset at the beggining of the 20th century when he and two Italian workers founded a mosaic fitting-room. The fitting-room followed a trend of establishing inlay fitting-room in other states of Europe apart from Italy on the beggining of 18th century. Although the fitting-room died out after Foester's wife death, it gave chance to the origin of Czech mosaic art which persists till nowadays. The second part describes changes in technology of this antique craft across centuries. Technology developement with accent on technical changes in work progress and...

A fire history study conducted for the Utah State University (USU) Experimental Forest using three distinct periods of fire frequency, historic (1700-1855), settlement (1856-1909), and suppression (1910-present), showed a decreased mean fire interval (MFI) during the settlement period and a greatly increased MFI during the suppression era. The difference was attributed to the influx of ignition sources during the settlement of the nearby Cache Valley, located 40 kilometers to the west. The interaction of settlers with the resource during logging and livestock grazing activities encouraged the high MFI and created the vegetal mosaic now observed on the study area. The elevation of the study area, 2377 m to 2651 m, places the site in the Engelmann spruce-subalpine fir zone (Picea engelmannii, Parry ex Engelm.-Abies lasiocarpa (Engelm. ex. Wats)). The suppression era and its corresponding increase in MFI has permitted the advancement of tolerant species in the understory of the intoleran lodgepole pine (Pinus contorta var. latifolia (Engelm. ex. Wats)) and aspen (Populus tremuloides Michx.). Continue suppression of disturbance from wildfire will allow the lodgepole pine cover type, which experienced the lowest MFI during the settlement period, to be further invaded by tolerant species, leading to a decrease in stand diversity and more intense fires when they do occur.

A dissertation presented by Sarah Jane Rogans to The Faculty of Science, University of the Witwatersrand, Johannesburg in fulfilment of the requirements for the degree of Doctor of Philosophy in the School of Molecular and Cell Biology. 2016 / Cassava (Manihot esculenta, Crantz) is considered to be an important food security crop consumed by over a billion peoples globally, many who subsist on it. Cassava mosaic disease (CMD) is one of the main biotic and economically important constraints to cassava cultivation in sub-Saharan Africa. Geminiviruses are the casual agents of CMD and cause disease to many staple food and cash crops of great economic importance worldwide. There are currently 11 species of Begomoviruses that belong to the Geminiviridae family. South African cassava mosaic virus (SACMV) is a circular ssDNA bipartite (DNA A and DNA B components) begomovirus belonging to the family Geminiviridae, and is one of the causal agents of cassava mosaic disease (CMD) endemic to southern Africa. Various strategies to control CMD are currently being investigated, one of which is cis-genics, which involves manipulation of endogenous host genes to combat viral pathogens. In order to achieve this, it is imperative to elucidate molecular mechanisms involved in host-virus interactions. Endogenous small RNAs (sRNAs), including microRNAs (miRNAs), have been found associated with gene regulatory mechanisms in response to virus infection. Amongst the non-coding host sRNAs targeting viruses are small interfering RNAs (siRNAs) associated with posttranscriptional gene silencing (PTGS) and transcriptional gene silencing (TGS), which are involved in the host RNA silencing pathway. The RNA silencing pathway is a highly conserved basal immunity pathway involved in host defence against plant viruses. The aim of this study was to identify siRNAs and miRNAs associated with gene regulatory mechanism in response to SACMV infection and to determine if they a play a role in the susceptible or recovery phenotype observed in SACMV tolerant cassava landrace TME3 or T200, respectively. Furthermore, virus-derived siRNA (vsRNA) populations targeting the DNA A and B components of SACMV were also investigated. MicroRNAs (miRNAs) are an important class of endogenous non-coding single-stranded small RNAs (21-24 nt in length), which serve as post-transcriptional negative regulators of gene expression in plants. Despite the economic importance of Manihot esculenta Crantz (cassava) only 153 putative cassava miRNAs (from multiple germplasm) are available to date in miRBase (V.21). Therefore, both conserved and novel miRNAs needed to be identified in cassava before we could determine what association they had with SACMV infection. In this part of the study, mature sequences of all known plant miRNAs were used as a query for homologous searches against cassava EST and GSS databases, and additional identification of novel and conserved miRNAs were gleaned from next generation sequencing (NGS) of two cassava landraces (T200 from southern Africa and TME3 from West Africa) at three different growth stages post explant transplantation and acclimatization. EST and GSS derived data revealed 259 and 32 conserved miRNAs in cassava, and one of the miRNA families (miR2118) from previous studies has not been reported in cassava. NGS data collectively displayed expression of 289 conserved miRNAs in leaf tissue, of which 230 had not been reported previously. Of the 289 conserved miRNAs identified in T200 and TME3, 208 were isomiRs. Thirty-nine novel cassava-specific miRNAs of low abundance, belonging to 29 families, were identified. Thirty-eight (98.6%) of the putative new miRNAs identified by NGS have not been previously reported in cassava. Several miRNA targets were identified in T200 and TME3, highlighting differential temporal miRNA expression between the two cassava landraces. This study contributes to the expanding knowledge base of the micronome of this important crop. MicroRNAs play a crucial role in stress response in plants, including biotic stress caused by viral infection. Viruses however can interfere with and exploit the silencing-based regulatory networks, causing the deregulation of miRNAs. This study aimed to understand the regulation of miRNAs in tolerant (TME3) and susceptible (T200) cassava landraces infected with SACMV. Next-generation sequencing was used for analysing small RNA libraries from infected and mock-inoculated cassava leaf tissue collected at 12, 32 and 67 dpi (days post-inoculation). The total number of differentially expressed miRNAs (normalized against mock-inoculated samples) across all three time points was 204 and 209 miRNAs, in TME3 and T200 infected plants, respectively, but the patterns of log2fold changes in miRNA families over the course of infection differed between the two landraces. A high number were significantly altered at 32 dpi when T200 and TME3 plants showed severe symptoms. Notably, in T200 69% and 28 (100%) of miRNA families were upregulated at 12 and 32 dpi, respectively. In contrast, TME3 showed an early pre-symptomatic response at 12 dpi where a high number (87%) of miRNAs showed a significant log2fold downregulation. Endogenous targets were predicted in the cassava genome for many of the identified miRNA families including transcription factors, disease resistance (R)-genes and transposable elements. Interestingly, some of the miRNA families (miR162, miR168 and miR403) that were significantly affected in both T200 and TME3 upon SACMV infection were shown to target proteins (DCL1, AGO1 and AGO2) that play important roles in the RNA silencing pathway. From results, we suggest that the early (12 dpi) miRNA response to SACMV in TME3 appears to involve PTGS-associated AGO1, DCL2 and a cohort of R genes belonging to the miR395 family which may prime the plant for tolerance and recovery downstream, while in T200, SACMV suppresses AGO1, AGO2 (at 32 and 67 dpi), and DCL2 (32 dpi) mediated RNA silencing, leading to severe persistent disease symptoms. This study provides insights into miRNA-mediated SACMV cassava interactions and may provide novel targets for control strategies aimed at developing CMD-resistance cassava varieties Endogenous small RNAs (sRNAs) associated with gene regulatory mechanisms respond to virus infection, and virus-derived small interfering RNAs (vsRNAs) have been implicated in recovery or symptom remission in some geminivirus-host interactions. Transcriptional gene silencing (TGS) (24 nt vsRNAs) and post transcriptional gene silencing (PTGS) (21-23 nt vsRNAs) have been associated with geminivirus intergenic (IR) and coding regions, respectively. In this Illumina deep sequencing study, we compared for the first time, the small RNA response to South African cassava mosaic virus (SACMV) of cassava landrace TME3 which shows a recovery and tolerant phenotype, and T200, a highly susceptible landrace. Interestingly, different patterns in the percentage of SACMV-induced normalized total endogenous sRNA reads were observed between T200 and TME3. Notably, in T200 there was a significant increase in 21 nt sRNAs during the early pre-symptomatic response (12 dpi) to SACMV compared to mock, while in TME3, the 22 nt size class increased significantly at 32 dpi. While vsRNAs of 21 to 24 nt size classes covered the entire SACMV DNA- A and DNA-B genome components in T200 and TME3, vsRNA population counts were significantly lower at 32 (symptomatic stage) and 67 dpi in tolerant TME3 compared with T200 (non-recovery). It is suggested that the high accumulation of primary vsRNAs, which correlated with high virus titres and severe symptoms in susceptible T200, may be due to failure to target SACMV-derived mRNA. In contrast, in TME3 low vsRNA counts may represent efficient PTGS of viral mRNA, leading to a depletion/sequestration of vsRNA populations, supporting a role for PTGS in tolerance/recovery in TME3. Notably, in TME3 at recovery (67 dpi) the percentage (expressed as a percentage of total vsRNA counts) of redundant and non-redundant (unique) 24 nt vsRNAs increased significantly. Since methylation of the SACMV genome was not detected by bisulfite sequencing, and vsRNA counts targeting the IR (where the promoters reside) were very low in both the tolerant or susceptible landraces, we conclude that 24 nt vsRNA-mediated RNA directed genome methylation does not play a central role in disease phenotype in these landraces, notwithstanding recognition for a possible role in histone modification in TME3. This work represents an important step toward understanding variable roles of sRNAs in different cassava genotype-geminivirus interactions. Also, by comparing the differences between a tolerant and susceptible host the aim is to achieve better understanding of the effect of pathogens on host sRNAome, an area that is deserving of me attention in plant systems. The expectation is that these findings presented in the PhD will contribute to the long-term goals of devising new methods of disease control against SACMV and understanding the complex interconnected mechanisms involved in virus-host interactome. / LG2017

A Thesis Submitted to the Faculty of Science, University of the Witwatersrand, Johannesburg, in fulfillment of the requirements for the Degree of Doctor of Philosophy / The Epidemiology, occurrences and effect of BMV (Brome Mosaic virus) wheat (triticum aestivum) in the summer rainfall area. (Abbreviation abstract) / AC 2018

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The objectives of this study were to determine the effects the temperature sensitivity of alleles of Rsv1 in soybean (Glycine max (L.) Merr.). Soybean cultivars carrying alleles of Rsv were exposed to 1 several heat treatments designed to induce heat shock protein production prior to inoculation with soybean mosaic virus (SMV). The heat treatment methods were similar to those employed in the research with N gene-tobacco mosaic virus studies. The soybean cultivars used were Lee 69, York, Kwanggyo, Ogden and PI96983, carrying the Rsv, Rsv1-y, Rsv1-k, Rsv1-t, and Rsv1 allles of Rsv1, respectively, and were selected to provide a range of reactions to selected SMV pathotype groups. For example Rsv1-y and Rsv1-k give a necrotic response to SMV G4 and SMV G6, respectively, while both are resistant to SMV G1. To determine the durability of resistance under heat shock conditions, the symptoms were observed for changes in the phenotype of the resistance response. Immunological techniques were employed to determine the vascular movement and localization of the viral antigen in the plant. Heat treatments used were found to induce HSP but to have no effect on the resistance phenotype. A detached leaf assay was used to test the same Rsv alleles at constant 1 high temperatures. Primary trifoliolate leaflets were removed and inoculated, then placed into a continuously lighted incubator at 20 °C or 30 °C. Leaf immunoprint assays were used to determine the localization of the viral antigen. The visible symptoms for necrotic lesions and veins were observed for necrotic phenotype-pathotype combinations but mosaic symptoms were not observed on detached leaves, as expected for inoculated leaves. The detached leaf assay confirmed that no change from the expected resistance response of the Rsv alleles occurred at 30 C. A breakdown 1 o of resistance to SMV at high temperature had been reported in soybean by Tu and Buzzell (1987). The resistance gene in which the high temperature breakdown occurred has been determined to be Rsv . Using cultivars and breeding lines carrying Rsv a similar experiment was attempted in growth 3 3 chambers. Preliminary results suggest that Rsv is temperature sensitive. / Master of Science

The spotted bird grasshopper, Schistocerca lineata Scudder (Orthoptera: Acrididae), is a widely distributed species found throughout most of the continental United States and southern Canada. This species is known to be highly variable in morphology, with many distinct ecotypes across its native range. These ecotypes display high levels of association with type-specific host plants. Understanding the evolutionary relationships among different ecotypes is crucial groundwork for studying the process of ecological differentiation. I examine four ecotypes from morphological and phylogeographic perspectives, and look for evidence of distinct evolutionary lineages within the species. I also begin to explore the potential role of the microbial community of these grasshoppers in ecological divergence by using 454 pyrosequencing to see if the microbial community structure reflects the ecology of the grasshoppers. I find support for a distinct aposematic lineage when approaching the data from a phylogeographic perspective and also find that this ecotype tends to harbor a unique bacterial community, different from that of a single other ecotype.

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