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Dissertation
Using crop genetic diversity to improve resilience: Agronomic potential of evolutionary breeding under differing management systems
(2019-03)
Mainly within organic and low-input cropping systems, evolutionary breeding based on the creation of heterogeneous evolving composite cross populations (CCPs) has been gaining attention. The aim of this dissertation is to assess the agronomic potential and yield stability of wheat CCPs in comparison to pure line varieties under differing management systems.
Three winter wheat CCPs were created in the UK in 2001, based on parental varieties that were selected for either their high yield or baking quality. The baking ...
Dissertation
Towards crop communities: exploring wheat diversity, wheat-pea species mixtures and farming practice in a food system context
(2022-06)
This thesis combines experimental work on heterogeneous crop populations (HP) and species mixtures (SM) with a social scientific and participatory approach. Chapter 1 introduces crop communities as a concept to integrate multiple approaches to diversify farming systems. HPs provide intraspecific and SM interspecific diversity in crop communities. A key challenge for the genetic improvement of HPs, especially for root traits is to combine effective selection to improve HPs while maintaining intraspecific diversity. ...
Dissertation
Resistance Based Integrated Pest Management Strategy for Globodera rostochiensis and Globodera pallida in Potato Cropping Systems
(2019-10)
Potato cyst nematodes (PCN), Globodera rostochiensis and G. pallida are important potato pests responsible for high yield losses globally. The ability of PCN to persist in the soil for a long time makes their management challenging and therefore these nematodes are under strict quarantine regulations in many countries. Nevertheless, both PCN species have recently been reported in potato cropping systems in Kenya. Resistant potato cultivars reduce nematode densities in the field below damage threshold levels and thus ...
Dissertation
Untersuchungen zur Bedeutung phytotoxischer Sirodesmine und zur induzierten Seneszenz in Interaktionen von Phoma lingam mit Brassica-Arten
(1995)
Ziel dieser Arbeit war es, die Bedeutung phytotoxischer Sirodesmine in Interaktionen von Phoma lingam mit Brassica napus und Brassica juncea zu untersuchen. Ein weiteres Interesse galt dem Einfluß einer induzierten Seneszenz auf die Resistenzeigenschaften.
Zur Isolierung von Sirodesmin PL wurde ein Säulenchromatographieverfahren auf Kieselgelbasis entwickelt. Mit dieser Methode konnten bis zu 100 µg Sirodesmin PL in reiner Form pro Arbeitsgang chromatographiert werden.
Sirodesmin PL wurde in verschiedenen Dosierungen ...
Dissertation
Isolation and characterisation of novel nematophagous fungi from eggs of the cereal cyst nematode Heterodera filipjevi and identifying their secondary metabolites with nematicidal activity
(2018-06-11)
Parasitism caused by cereal cyst nematodes (CCNs) is a major limiting biotic factor in cereal cropping systems. CCNs attack cereal crops and can lead to significant yield reductions. Field observations in experimental wheat fields of the International Maize and Wheat Improvement Centre (CIMMYT) in Turkey had revealed a sharp decline in nematode populations of the cereal cyst nematode Heterodera filipjevi. Microscopic studies of the cyst samples obtained from these fields regularly demonstrated the presence of fungi ...
Dissertation
The Suppressive Nature of Compost against Pythium spp: evaluation of compost-based applications in two host pathogen systems using bioassays and molecular fingerprinting
(2018-08-14)
The suppressive effect of composts on soil-borne plant pathogens has been widely reported in the scientific literature. However, the role of the compost microbiome, in this respect, is still not well understood. The general goal of this research was the molecular-biological characterisation of the microbiomes of two compost types within the host-pathogen system Pythium ultimum and cucumber, thereby contributing to understanding the role of the microbial structure of the chosen composts in this specific system. An ...
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
Agrobiodiversity through evolutionary plant breeding – System specific adaptation of agronomic and morphological traits and effective populations size in composite cross populations of winter wheat
(2018-02-05)
Der Schwerpunkt der vorliegenden Arbeit ist die Beschäftigung mit Züchtungsmethoden, die eine Erhöhung der Agrobiodiversität mit sich bringen, außerdem werden die Auswirkungen diversifizierter Anbausysteme betrachtet.
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
Evaluation of Pathological Risks Associated with Use of Leguminous Cover crop and Living mulch species
(2017-11-15)
In the past 10 to 15 years, there has been a tendency in Europe to switch from cereal based cropping systems, with winter and summer fallow, to cropping systems which combine greater crop diversity with maximum soil cover. Increasing the opportunities of including legumes into crop rotations to be grown as cover crops, intercropped or under-sown with cereals can provide multiple beneficial services to agro-ecosystems. A major concern is however, that many of the leguminous species of interest share important soil-borne ...