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Postgenomic studies of Candida albicansMartchenko, Mikhail. January 2007 (has links)
No description available.
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Functional genomics : analysis of polytene region 38 of Drosophila melanogasterButler, Heather January 1999 (has links)
No description available.
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Detection of markers in a low density region of the barley (Hordeum vulgare L.) genome and their effects on the mapping of quantitative traitsCampeol, Nadia. January 1998 (has links)
No description available.
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Invasive alien plants of South Africa’s freshwater systems : accelerating identification of species and climatically suitable areas for species invasionHoveka, Lerato Nakedi 01 July 2014 (has links)
M.Sc. (Botany) / In South Africa, controlling and eradicating Azolla filiculoides and Eichhornia crassipes cost annually approximately US$ 60 million to the national budget. However, the success of these operations is mixed because invasive aquatic plants often spread very rapidly either before they are spotted or before decisions are taken to implement control actions. This limitation is further exacerbated by difficulties in determining the invasion potential of newly introduced or unknown aquatic plants, as well as difficulties inherent to species identification. Resolving these drawbacks requires pre-emptive actions such as identifying areas that are most vulnerable to invasion by alien plants. In this study, I first explore whether molecular technique such as DNA barcoding can be useful to: i) overcome potential limitation of morphology-based identification of invasive aquatic plants; and ii) establish successful control of these invasives. For this purpose, I tested the utility of official DNA barcodes (rbcLa + matK or core barcodes), trnH-psbA, and the core barcode + trnH-psbA to identify invasive aquatic plants of South Africa’s freshwaters. Second, I use the technique of ecological niche modeling to identify most vulnerable freshwater systems to species invasion under current and climatic conditions. My analysis indicates that the core barcodes and matK regions perform poorer compared to trnH-psbA, which provides 100% successful identification alone or in combination with the core barcodes. This study therefore validates trnH-psbA as single best DNA barcode for invasive alien aquatic plants of freshwater systems in South Africa. Using this DNA region in BLAST analysis to screen plants species sold in aquarium market in Johannesburg, I found surprisingly that some prohibited species are already in circulation in the market. These include Hydrilla verticillata, egeria densa, Myriophyllum spicatum, and Echinodorus cordifolius. Furthermore, based on climatic parameters, I explored the distribution of the "bad five" aquatic species in South Africa, i.e. the most damaging invaders of freshwater systems. I found distinct distribution potentials for these species under current climatic conditions. Overall, 38% of all South Africa’s dams occur in areas climatically vulnerable to the invasion by the bad five with the Western Cape Province being the most vulnerable. However, under predicted climate change scenario, I found evidence for contrasting shifts in species range: species such as Azolla filiculoides, Eichhornia crassipes, Salvinia molesta might increase their range by at most 2% whilst the ranges of Myriophyllum aquaticum and Pistia stratiotes might contract by at most 5%. This range contraction and expansion will result in some dams currently vulnerable to invasion becoming resilient whilst others that are currently resilient might become vulnerable owing to climate change. This result demonstrates not only the utility of DNA barcoding in implementing control measures, but also provides ways of prioritising control/management efforts.
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Genetic mapping of gray leaf spot resistance genes in maizeLehmensiek, Anke 12 1900 (has links)
Thesis (PhD)--Stellenbosch University, 2000. / ENGLISH ABSTRACT: Gray leaf spot (GLS) of maize, caused by the fungus Cercospora zeae-maydis,
can reduce grain yields by up to 60% and it is now recognized as one of the most
significant yield-limiting diseases of maize in many parts of the world. The most
sustainable and long-term management strategy for GLS will rely heavily on the
development of high-yielding, locally adapted GLS resistant hybrids.
Molecular markers could be useful to plant breeders to indirectly select for genes
affecting GLS resistance and to identify resistance genes without inoculation and
at an early stage of plant development. Only two studies in the USA have
examined quantitative trait loci (QTL) association with GLS resistance.
The aim of this study was to map GLS resistance genes in a resistant Seed Co
LTD, Zimbabwean inbred line. Molecular markers linked to the GLS resistance
QTL were identified by using the amplified fragment length polymorphism (AFLP)
technique together with bulked segregant analysis. Eleven polymorphic AFLP
fragments were identified and converted to sequence-specific PCR (polymerase
chain reaction) markers. Eight of the 11 converted AFLP markers were added to
the maize marker database of the University of Stellenbosch.
Five of the 8 converted AFLP markers were polymorphic between the resistant
and the susceptible parent. They were amplified on the DNA of 230 plants of a
segregating F2 population and linkage analysis was performed with
MAPMAKER/EXP. Two linkage groups consisting of two markers each, with a
linkage distance of 10.4 cM (LOD 22.83) and 8.2 cM (LOD 55.41) between the
two markers, were identified. QTL mapping with MAPMAKER/QTL confirmed the
presence of QTL in both linkage groups. Two publicly available recombinant inbred families (Burr et a/., 1988) were used
to localize the converted AFLP markers on the genetic map of maize. The QTL,
which were identified with the AFLP markers, were mapped to chromosomes 1
and 5. Another AFLP marker was mapped to chromosome 2 and a further to
chromosome 3.
To obtain more precise localizations of the QTL on chromosomes 1 and 5,
sequence-tagged site markers and microsatellite markers were used. The
markers were amplified on the DNA of the 230 plants of the F2 population and
linkage analysis was performed with MAPMAKER/EXP. The order of the markers
was in agreement with the UMC map of the Maize Genome Database. Interval
mapping using MAPMAKERlQTL and composite interval mapping using QTL
Cartographer were performed. The QTL on chromosome 1 had a LOD score of
21 and was localized in bin 1.05/06. A variance of 37% was explained by the
QTL. Two peaks were visible for the QTL on chromosome 5, one was localized in
bin 5.03/04 and the other in bin 5.05/06. Both peaks had a LOD score of 5 and
11% of the variance was explained by the QTL.
To test the consistency of the detected QTL, the markers flanking each QTL
were amplified on selected plants of two F2 populations planted in consecutive
years and regression analysis was performed. Both the QTL on chromosome 1
and the QTL on chromosome 5 were detected in these populations. Furthermore,
the presence of a QTL on chromosome 3 was confirmed with these populations.
A variance of 8 -10% was explained by the QTL on chromosome 3.
In this study, a major GLS resistance QTL was thus mapped on chromosomes 1
and two minor GLS resistance QTL were mapped on chromosomes 3 and 5
using a resistant Seed Co LTD, Zimbabwean inbred line. Markers were identified
which could be used in a marker-assisted selection program to select for the GLS
resistance QTL. / AFRIKAANSE OPSOMMING: Grys blaarvlek (GBV) van mielies, veroorsaak deur die swam Cercospora zeaemaydis,
kan graanopbrengs met tot 60% verlaag en word beskou as een van die
vernaamste opbrengs-beperkende siektes wêreldwyd. Die toepaslikste
langtermyn stragtegie vir GBV beheer sal wees om plaaslike mieliebasters met
hoë opbrengs en GBV weerstand te ontwikkel.
Molekulêre merkers kan nuttig deur plantetelers gebruik word om
weerstandsgene te selekteer. Seleksie is moontlik in die afwesigheid van
inokolum en op 'n vroeë stadium van plant ontwikkeling. Slegs twee vorige
studies (in die VSA) het kwantitatiewe-kenmerk-Iokusse (KKL), vir GBVweerstand
ondersoek.
Die doel van hierdie studie was om die GBV weerstandsgene in 'n
weerstandbiedende ingeteelde lyn (Seed Co BPK, Zimbabwe) te karteer.
Molekulêre merkers gekoppel aan die GBV weerstands KKL is geïdentifiseer
deur gebruik te maak van die geamplifiseerde-fragmentlengte-polimorfisme-
(AFLP-) tegniek en gebulkte-segregaat-analise. Elf polimorfiese merkers is
geïdentifiseer en omgeskakel na volgorde-spesifieke PKR (polimerase
kettingreaksie) merkers. Agt van die elf omgeskakelde AFLP-merkers is by die
mieliemerker databasis van die Universiteit van Stellenbosch gevoeg.
Vyf van die 8 omgeskakelde AFLP-merkers was polimorfies tussen die bestande
en vatbare ouers. Hulle is geamplifiseer op die DNA van 230 plante van 'n
segregerende F2-populasie en is gebruik in 'n koppelingstudie met
MAPMAKER/EXP. Twee koppelingsgroepe, elk bestaande uit twee merkers, met
onderskeidelik koppelingsafstande van 10.4 eM (LOD 22.83) en 8.2 eM (LOD
55.41) tussen die merkers, is geïdentifiseer. KKL-kartering het getoon dat KKL in
albei koppelingsgroepe aanwesig is. Twee kommersieël beskikbare, rekombinant-ingeteelde families (Burr et aI.,
1988) is gebruik om die omgeskakelde AFLP-merkers op die mielie genetiese
kaart te plaas. Die KKL wat met die AFLP-merkers geïdentifiseer is, is gekarteer
op chromosome 1 en 5. 'n Verdere AFLP-merker is op chromosoom 2 gekarteer
en 'n ander op chromosoom 3.
Ten einde die KKL op chromosome 1 en 5 meer akkuraat te karteer, is volgordege-
etikeerde en mikrosatelliet merkers gebruik. Die merkers is geamplifiseer op
die DNA van die 230 plante van die F2-populasie en koppelings-analises is
uitgevoer. Die volgorde van die merkers was dieselfde as die van die UMC-kaart
in die Mielie Genoom Databasis. Interval kartering met MAPMAKER/QTL en
komposiet interval kartering met QTL Cartographer is uitgevoer. Die KKL op
chromosoom 1 het 'n LOD-telling van 21 gehad en is in bin 1.05/06 geplaas. Die
KKL was verantwoordelik vir 37% van die variansie. Twee pieke was
onderskeibaar vir die KKL op chromosoom 5, een in bin 5.03/04 geleë en die
ander in bin 5.05/06. Elke piek het 'n LOD-telling van 5 gehad en die twee KKL
was verantwoordelik vir 11% van die variansie.
Om die herhaalbaarheid van die effek van die KKL te toets is die merkers naaste
aan elke KKL geamplifiseer op geselekteerde plante van twee F2-populasies wat
in opeenvolgende jare geplant is. Regressie analise is op die data gedoen. Beide
die KKL op chromosoom 1 en die KKL op chromosoom 5 kon in hierdie
populasies geïdentifiseer word. Verder kon die aanwesigheid van 'n verdere KKL
op chromosoom 3 in hierdie populasies bevestig word. Laasgenoemde KKL was
verantwoordelik vir 8-10% van die totale variansie.
In hierdie studie is daar dus 'n hoof GBV-weerstands KKL gekarteer op
chromosoom 1 en twee kleiner GBV-weerstands KKL gekarteer op chromosome
3 en 5. Merkers is geïdentifiseer wat moontlik in merker-gebaseerdetelingsprogramme
gebruik kan word om plante te selekteer wat die GBVweerstands
KKL het.
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Map-based cloning of the NIP gene in model legume Medicago truncatula.Morris, Viktoriya 05 1900 (has links)
Large amounts of industrial fertilizers are used to maximize crop yields. Unfortunately, they are not completely consumed by plants; consequently, this leads to soil pollution and negative effects on aquatic systems. An alternative to industrial fertilizers can be found in legume plants that provide a nitrogen source that is not harmful for the environment. Legume plants, through their symbiosis with soil bacteria called rhizobia, are able to reduce atmospheric nitrogen into ammonia, a biological nitrogen source. Establishment of the symbiosis requires communication on the molecular level between the two symbionts, which leads to changes on the cellular level and ultimately results in nitrogen-fixing nodule development. Inside the nodules hypoxic environment, the bacterial enzyme nitrogenase reduces atmospheric nitrogen to ammonia. Medicago truncatula is the model legume plant that is used to study symbiosis with mycorrhiza and with the bacteria Sinorhizobium meliloti. The focus of this work is the M. truncatula nodulation mutant nip (numerous infections and polyphenolics). The NIP gene plays a role in the formation and differentiation of nodules, and development of lateral roots. Studying this mutant will contribute knowledge to understanding the plant response to infection and how the invasion by rhizobia is regulated. Previous genetic mapping placed NIP at the top of linkage group 1 of the M. truncatula genome. A NIP mapping population was established with the purpose of performing fine mapping in the region containing NIP. DNA from two M. truncatula ecotypes A17 and A20 can be distinguished through polymorphisms. Positional mapping of the NIP gene is based on the A17/A20 genetic map of M. truncatula. The NIP mapping population of 2277 plants was scored for their nodulation phenotype and genotyped with flanking molecular genetic markers 146o17 and 23c16d, which are located ~1.5 cM apart and on either side of NIP. This resulted in the identification of 170 recombinant plants, These plants' DNAs were tested further with different available genetic markers located in the region of interest, to narrow the genetic interval that contains the NIP gene. Segregation data from genotyping analysis of recombinant plants placed NIP in the region between 4L4 and 807 genetic markers.
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Regeneration Patterns and Facilitation Following Blowdown in a Self- Replacing Lodgepole Pine (Pinus contorta) Stand in Central OregonKarps, Jennifer Michelle 16 February 2006 (has links)
Nurse plant and object facilitation is an important factor mitigating abiotic stress, improving seedling recruitment, and shaping the fine-scale spatial patterns of many plant communities. I investigate the role of facilitation on lodgepole pine regeneration following blowdown in central Oregon. My objective is to examine the importance of nurse objects on seedling recruitment under varying stand conditions. I base my analysis on 1) the mapped locations and attributes of seedlings, saplings, trees, shrubs, snags, stumps, and sound and decomposed logs in each of five, 500 m2 circular plots, 2) water holding capacity estimates of woody and leafy litter and pumice soil, and 3) growing-season air temperatures. My analysis identifies seedling patterns at multiple spatial scales (~0-8 m) using nearest neighbor and Ripley’s K statistics and identifies differences in canopy structure, seedling development, and temperature using non-parametric rank-sum tests.
My results show blowdown severity varies with pre-disturbance stand structure, resulting in a multi-modal stand structure with a wide range of canopy and seedling microhabitat conditions. Stand-wide, post-blowdown regeneration patterns reveal >80% of seedlings grow near nurse shrubs, logs, and woody litter, suggesting preferential germination and survival in these microhabitats. High seedling densities correspond with median shrub diameters, and up to 38% of seedlings grow near recently downed logs, indicating both shrubs and logs serve as important nurse objects. The role of nurse objects in mitigating moisture stress is implicated by the potentially high evaporative stress under extreme growing season temperatures in areas of severe blowdown and by the high moisture-holding capacity of woody litter relative to the pumice soil. Stand-wide, 91% of all seedlings and 87% of all shrubs grow on woody litter, and seedlings growing on woody litter show the greatest development.
The positive spatial correlation of seedlings and shrubs with nurse plants and woody litter supports the assertion that both are important facilitators for seedling regeneration and emerging spatial patterns of stand recovery. These results have important management implications, suggesting that the removal of nurse plants and objects through salvage logging or prescribed burning may have negative long-term impacts on local and regional forest regeneration.
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Location and expression of genes related to the cytoplasmic male sterility system of Brassica napusGeddy, Rachel Gwyneth. January 2006 (has links)
No description available.
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Early-flowering mutants of a late-flowering ecotype of Arabidopsis thalianaWilson, Dale, 1972- January 2001 (has links)
Abstract not available
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Genetic characterisation and QTL mapping of zinc nutrition in barley (Hordeum vulgare)Lonergan, Paul Francis. January 2001 (has links) (PDF)
Includes bibliographical references (leaves 192-211). Maps major genes or quantitative trait loci associated with zinc nutrition in the vegetative and reproductive tissues of barley (Hordeum vulgare)
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