• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 1
  • 1
  • 1
  • Tagged with
  • 151
  • 27
  • 22
  • 22
  • 7
  • 6
  • 5
  • 5
  • 5
  • 5
  • 4
  • 4
  • 3
  • 3
  • 3
  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Effect of fertilisation, crop protection, pre-crop and variety choice on yield of phenols content diseases severity and yield of winter wheat

Almuayrifi, Mohammed Saleh B. January 2013 (has links)
There is increasing pressure from government legislation and supermarket quality assurance schemes to reduce chemosynthetic pesticide-inputs in conventional production systems. This has resulted in the need to study potential management based approaches to develop alternative management (e.g. rotational design or crop nutrition) strategies and/or crop breeding/variety selection based approaches to reduce disease pressure or crop resistance to biotic stress. Two long-term, factorial field trials (the NSCS and the NUE-crops trials) were used to assess effects of fertiliser input types (composted manure vs mineral fertilisers), fertiliser input levels, pre-crop/rotational position, crop protection (with and without the use of chemosynthetic pesticides) and wheat genetics/variety choice on phenolic profiles in flag leaves, foliar disease severity and grain yield in winter wheat. Interactions between crop management practices and growing season were investigated using univariate and redundancy analysis approaches. Flag leaf concentrations of phenolic compounds differed between years and plant growth stages and were higher (approx 40%) in crops fertilised with organic compared to mineral fertilisers, but there were virtually no effects of crop protection on phenolic profiles. In contrast, both disease severity and crop yield were significantly affected by crop protection and fertilisation practices. The use of conventional, pesticide based crop protection resulted in lower disease severity and higher yields and mineral NPK fertilisers resulted in lower Septoria and higher mildew and stripe rust severity. Effects of precrop/rotational position and wheat genetics/variety choice, and interactions between precrop, fertilisation, crop protection and/or variety choice were also detected for phenolic profiles, disease severity and grain yield. RDA identified (a) positive associations between organic fertilisation and radiation, and concentrations of phenolic compounds in leaves, (b) positive associations between organic crop protection and relative humidity, and disease severity and (c) negative associations between concentrations of most phenolic compounds and disease severity. Results indicate that it is possible to increaseing concentrations of phenolic compounds in cereals via changes to fertilisation practices, and that this may (a) reduce disease severity and/or increase crop yield in cropping systems which omit chemosynthetic pesticides, but (b) may have no effect on disease and reduced crop yields in cereal cropping systems which use pesticides. However, varietal differences in leaf phenolic expression under organic fertilisation could not be linked to differences in disease severity and yields.
2

Identification of pathogens and control of spot blotch disease of barley (Hordeum vulgare) by combining plant resistance and biological control

Aada, Abdallah January 2013 (has links)
Spot blotch is one of the most important diseases of barley (Hordeum vulgare) in Libya and worldwide. The overall aim of this study was to investigate the potential of biological control in combination with disease resistance to control spot blotch without the potential hazards of chemical application. Fungi were isolated from barley plants with spot blotch symptoms from different areas in Libya. As well as the commonly known spot blotch pathogen Bipolaris sorokiniana (teleomorph Cochliobolus sativus), Bipolaris spicifera (teleomorph Cochliobolus spicifer), Curvularia inaequalis, and Alternaria alternata were identified by their morphology and ribosomal DNA sequences. Bipolaris sorokiniana was the most serious pathogen under the test conditions; the others infected barley but caused less severe symptoms. Spot blotch resistance of barley seedlings was tested under greenhouse conditions with four Libyan cultivars (ACSAD, Nibola, Rehan, and Wadi Utbah) and two UK cultivars (Gaelic and Pastoral). Nibola was the most resistant. The ability of the organisms in three commercial biocontrol products, Trichoderma harzianum T-22 (Trianum), Streptomyces lydicus WYEC 108 (Actinovate) and Bacillus subtilis QST 713 (Serenade), to control spot blotch individually and in combination was investigated. On agar plates, all three inhibited growth of the pathogens completely on the second day of culture, except that for B. spicifera with S. lydicus there was an inhibition zone and the pathogen grew in the opposite direction. Disease severity was lowest when T. harzianum T-22 was applied individually to the most resistant cultivar, Nibola. Foliar application, soil treatment and seed coating all reduced disease severity. With foliar application, T. harzianum T-22 was more effective when applied at the same time as the pathogen than when applied one week before or four days after. In a field experiment with T. harzianum T-22, foliar application combined with seed treatment suppressed spot blotch more effectively than either method individually.
3

Identification of radiation use efficiency traits in a wheat and spelt population

Chuong, Nguyen Duc Xuan January 2014 (has links)
Wheat is one of the main staple food crops, providing an essential source of carbohydrates for millions of people. Therefore, demand for wheat will increase in next few decades as the global population increases toward a prediction 9 billion by 2050. Further advances in wheat yield requires the integration of new tools and strategies to complement traditional approaches to select genotypes that are better suited to abiotic stress, in the context of climate change. Identifying morphological and physiological characters, correlated with tolerance to environmental stress, is a priority for wheat breeders. One approach that can be combined in wheat breeding programmes is to create new genetic variation, for example by crossing wheat with close relatives such as spelt. The overall objective of this study is to investigate the physiological traits associated with radiation use efficiency (RUE) in a segregating population of 225 recombinant inbred lines, originating from the cross of wheat (cv. Forno) with spelt (cv. Oberkulmer). Three field experiments from 2010 to 2012 were carried out at Sutton Bonington. All lines, and their parents, were grown as ear rows in 2010 and arranged in randomized design with one replicate of mini plots in 2011. In 2012 three replicates were grown in a randomised complete block design. In these experiments, plant development, RUE, biomass, grain yield and associated physiological traits were measured in the recombinant inbred lines. In addition, a glasshouse experiment was conducted in 2013 to investigate gas exchange traits amongst 18 selected lines with a wide range of RUE, alongside the parents.
4

Phenotypic and genetic analysis of yellow rust resistance in the UK winter wheat cultivar Claire

Powell, Nicola Michelle January 2010 (has links)
Yellow rust resistance in the winter wheat cultivar Claire is considered durable, as Claire has been grown extensively within the UK for over 10 years and the resistance has remained effective. To characterise this potentially durable source of resistance a doubled haploid (DH) population was produced between Claire and the yellow rust susceptible cultivar Lemhi. Construction of a genetic linkage map, together with phenotypic data allowed the estimation of the number, chromosomal position and degree of effect of yellow rust resistant QTL(s). Claire was found to exhibit a quantitative, adult plant resistance phenotype (APR) controlled by two major QTLs, both located on chromosome 2DL (QTLAPR.2Da and QTLAPR.2Db) and two minor QTLs, located on 2BL (QTLAPR.2B) and 7BL (QTLAPR.7B). These QTLs act additively to achieve a resistance response that has remained effective since Claire’s release in 1999. Marker loci associated with the two major QTLs and knowledge of Claire’s pedigree suggests QTLAPR.2Da could be a APR QTL, known to confer complete immunity to yellow rust, originating from the winter wheat cultivar Alcedo and that QTLAPR.2Db is the durable yellow rust resistance gene Yr16 derived from Cappelle-Desprez. However, DH lines containing QTLAPR.2Da exhibited either a complete or partial yellow rust resistance indicating a potential suppressor effect against the resistant phenotype conferred by this major QTL could be segregating within the population. Analysis of transcript levels of defence genes was used to examine the effect of the hypothesized suppressor on the expression of basal defence in DH lines containing QTLAPR.2Da. No correlation between the presence of the hypothesized suppressor and expression of basal defence genes was observed. The identification of four APR QTLs in Claire and a potential suppressor in Lemhi that affects QTLAPR.2Da will serve as a precursor to help elucidate the defence mechanisms of the yellow rust resistance in Claire.
5

A micrometeorological study on the effect of water stress on growth and yield of wheat (triticum aestivum L.) in arid climate

Abdullah, M. A. January 1980 (has links)
The objective was to investigate the possibility of imposing water stress at particular stages of wheat development without much affecting the final yield. This is important in planning for scheduling irrigation in Egypt to use water in the most economic way. Crops were grown in 1977 and 1978 with two water treatments in each year. Detailed micrometeorological measurements were made. Plant measurements were used to follow the growth and development of the crops and to estimate their final yields. The crop water budgets were estimated from measurements of soil water content.
6

Ecological and sociological aspects of the Phalaris minor epidemic in the rice-wheat system of Haryana, India

Franke, Angelinus Cornelius January 2005 (has links)
No description available.
7

The evolution of the cytosolic pathway of ADP-glucose synthesis in cereal endosperm

Rösti, Sandrine January 2006 (has links)
No description available.
8

A study of the bionomics and control of Sitophilus zeamais (Motschulsky) and Sitotroga cerealella (Oliver), and associated fauna in stored maize under laboratory and field conditions in Kenya

De Lima, C. P. F. January 1978 (has links)
No description available.
9

Investigating secondary metabolism in Zymoseptoria tritici

Ali, Solaf Jawhar January 2015 (has links)
One of the most serious fungal diseases of wheat is Septoria tritici Blotch caused by Zymoseptoria tritici. This disease is typified by an asymptomatic latent phase, followed by a rapid onset on host-cell necrosis. There has long been debate about whether the necrosis is due to production of secondary metabolite toxins or other effects of the fungus such as use of small protein effectors thereby providing nutrients for fungal growth. Secondary metabolites are mainly classified into polyketides (PKs), non-ribosomal peptides (NRPs), alkaloids and terpenes. Genome analysis of Z. tritici identified nine PKS and two hybrid PKS NRPS pathways in addition to the NRPS believed to be responsible for siderophore biosynthesis. Promoter: GFP fusions were made for all of these candidate toxin synthase genes and their expression followed in vitro and through the disease cycle by confocal microscopy, however only pPKS3 gave any apparent GFP expression in planta. Disruption of PKS3 did not generate any mutant phenotype. In fungi, the phosphopantetheine transferase (PPTase) is needed not only for the PKS and NRPS activation, but also both lysine and siderophore synthesis and its disruption in Z. tritici is reported to have very reduced virulence. The Z. tritici alpha-aminoadipate reductase (Lys2) gene was disrupted and the ZtΔlys2 mutant was auxotrophic for lysine. Furthermore, the pathogenicity testing of ZtΔlys2 on wheat showed a significant reduction in symptom development and the pycnidia and spore number compared with a wild type. In a parallel experiment, ornithine N hydroxylase (SidA) was disrupted to prevent hydroxamate siderophore synthesis. The resulting ZtΔlys2 mutant was unable to synthesise ferrichrome and required supplementation with a high concentration of iron. It was more sensitive to oxidative stress compared with wild type and showed reduction of pycnidia and spore numbers. Whilst L1PPTstrain shows reduced virulence, the impacts of lysine and iron uptake are sufficient to account for the reduction in virulence so given that these genes also had very low if any expression in planta, it is unlikely that PKS and hybrid PKS NRPS play a major role in disease of Z. tritici.
10

Some aspects of the nature of resistance in barley varieties to rhynchosporium secalis

Ives, S. M. January 1979 (has links)
No description available.

Page generated in 0.0205 seconds