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Dissertation
Genetic variation of and environmental effects on inducibility of resistance in tomatoes (Solanum lycopersicum L.) to Phytophthora infestans (Mont) de Bary
(2010-12-02)
Many plant strengtheners are promoted for their supposed effects on nutrient uptake and/or resistance induction (IR). In addition, many organic fertilizers are supposed to enhance plant health and several studies have shown that tomatoes grown organically are more resistant to late blight, caused by Phytophthora infestans to tomatoes grown conventionally. Much is known about the mechanisms underlying IR. In contrast, there is no systematic knowledge about genetic variation for IR. Therefore, the following questions ...
Dissertation
Development and Integration of Biocontrol Products in Branched Broomrape (Phelipanche ramosa) management in Tomato
(2012-10-19)
Parasitic weeds of the genera Striga, Orobanche, and Phelipanche pose a severe problem for agriculture because they are difficult to control and are highly destructive to several crops. The present work was carried out during the period October, 2009 to February, 2012 to evaluate the potential of arbuscular mycorrhizal fungi (AMF) to suppress P. ramosa on tomatoes and to investigate the effects of air-dried powder and aqueous extracts from Euphorbia hirta on germination and haustorium initiation in Phelipanche ramosa. ...
Dissertation
Pathogens occuring in the winter pea-maize-winter wheat rotation, their host specificity and the potential of compost in suppressing foot and root disease of peas
(2015-09-17)
The overall aim of the work presented was to evaluate soil health management with a specific focus on soil borne diseases of peas. For that purpose field experiments were carried out from 2009 until 2013 to assess crop performance and pathogen occurrence in the rotation winter pea-maize-winter wheat and if the application of composts can improve system performance. The winter peas were left untreated or inoculated with Phoma medicaginis, in the presence or absence of yard waste compost at rate of 5 t dry matter ha-1. ...
Dissertation
Etiology of Maize Root rot in Oman: Causal agents and effects of a compost based organic growing system
(2018-08-16)
Summary:
In Oman, the main cereal crop Maize is facing serious problems due to high salinity, alkaline soils with low organic matter, high temperatures, and root rot diseases. Production peaked at 40,000 t in 2011 but dropped to less than 15,000 t in 2014.
A survey on maize root rot in eight maize growing governorates in Oman yielded nine fungal and oomycetes species of which Pythium arrhenomanes and Fusarium fujikuroi were first reports on maize in Oman. Both are able to attack multiple hosts. Under controlled ...
Dissertation
Studies on the diversity of the main necrotrophic pathogens on wheat and barley Pyrenophora tritici-repentis and Cochliobolus sativus
(2017-10-30)
Leaf blights such as tan spot of wheat (Pyrenophora tritici-repentis) and spot blotch of barley (Cochliobolus sativus) are among the main constraints in achieving high and stable yields and are the main concerns among the several intrinsic drawbacks of narrow cropping sequencesas both are residue borne. The development of useful and durable resistance against prevalent races requires detailed information on the virulence diversity of the pathogen and the type of resistances available in the host. Thus, the focus of ...
Dissertation
The status and barriers to the implementation and continuation of the school gardening projects in Germany, Nigeria and the United States of America
(2010-10-25)
In drawing a conclusion for this study, care must be taken in generalizing findings since the population of students and teachers investigated were limited to certain levels in the different schools and countries. This study recognized some complexity of the factors underlying the status of school gardening instruction and activities in Germany, Nigeria and the U.S. as inadequate time for decision-making in the process of gardening, motivation of teachers and students. This was seen as the major impediments that ...
Dissertation
Analyzing Gene Centres with the Help of the Checklist Method – the Case of Syria
(2016-06-07)
The present survey of species diversity of cultivated plants is the first for Syria. Some cultivated species will be added in the future, because due to the civil war in Syria, it was not possible to visit the country in the frame of the present work, as initially planned. Checklists proved to be a useful tool for overviewing the cultivated plants of selected areas and allow a characterization of the state of plant genetic resources of Syria.
Syria has experienced several civilizations. Man settled in this productive ...
Dissertation
Amount, composition and turnover of organic matter in topsoils and subsoils under mature beech forest
(2017-12-15)
Two-third of the terrestrial carbon (C) is stored in soils, and up to 63 % of the soil organic C (SOC) is stored in subsoils (i.e. below 30 cm soil depth). Forest soils account for nearly 70 % of the global SOC, demonstrating their great importance regarding the global carbon cycle. The higher average age of the OC stored in subsoil indicates that the subsoil OC is more stable against microbial decomposition. The capability of soil to stabilize OC is affected by substrate characteristics (e.g. size, distribution, ...
Dissertation
Effects of tillage intensity on soil C, N, and P pools with different stability
(2013-11-29)
Es ist bekannt, dass die Umsatzdynamik der organischen Substanz von der Bodenbearbeitungsintensität abhängt. Bis jetzt sind nur wenige Daten zum Einfluss der Bearbeitungsintensität und des Zwischenfruchtanbaus auf C-, N-, und P-Dynamik im Ober- (0-5 cm Tiefe) und Unterboden (5-25 cm Tiefe) von Lössböden verfügbar. Hauptziele dieser Arbeit waren die (i) Quantifizierung des Einflusses von verschiedenen langzeitig durchgeführten Bearbeitungssystemen auf labile, intermediäre, und passive C- und N-Pools; (ii) Quantifizierung ...
Dissertation
Effects of grassland renovation on carbon concentrations and aggregate distribution in temperate grassland soils
(2013-12-05)
The effects of continuous tillage on the distribution of soil organic matter (SOM) and aggregates have been well studied for arable soils. However, less is known about the effects of sporadic tillage on SOM and aggregate dynamics in grassland soils. The objectives of the present thesis were (I) to study the longer-term effects of sporadic tillage of grassland on organic carbon (Corg) stocks and the distribution of aggregates and SOM, (II) to investigate the combined effects of sporadic tillage and fertilization on ...