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Isolation of early-responsive ncRNA from the wheat-Russian wheat aphid interactionNicolis, Vittorio F. 09 December 2013 (has links)
M.Sc. (Botany and Plant Biotechnology) / Wheat (Triticum aestivum L.) is the one of the three most extensively cultivated cereal crops worldwide (Shewry, 2009). In South Africa, wheat is cultivated in both summer and winter rainfall regions as monocultures typical to modern industrialised agriculture. Monocultures provide uniform crop quality and allow processes such as planting and harvesting to be mechanised (Altieri et al., 2009). However, the genetically homogeneous nature of monocultures increases the vulnerability of the crop to both biotic and abiotic stresses (Faraji, 2011). Future food production is challenged by predicaments such as an increasing human population while the ratio of arable land to population is decreasing. Yield losses of wheat due to biotic factors alone were estimated as 29 % (2001-2003) (Oerke, 2006). The need to reduce the gap between attainable yield and actual yield is therefore crucial in order to maximise crop production for future food security (Duveiller et al., 2007). One of the most damaging pests to worldwide wheat production is the Russian wheat aphid (RWA), Diuraphis noxia (Kurdjumov) (Arzani et al., 2004). A native pest of central Asia, the RWA has spread to all cereal producing areas of the world with the exception of Australia (Burd et al., 2006). While feeding on susceptible hosts, the aphid injects an eliciting agent into the host, which causes the breakdown of the chloroplast and cellular membranes, leading to the appearance of symptoms typical of RWA feeding, including leaf rolling (Botha et al., 2005). Leaf rolling creates a sheltered environment for the aphid from insecticides and predators, and this together with their parthenogenic and viviparous reproductive nature makes their rapid increase in numbers extremely difficult to control (Goggin, 2007). Resistant wheat genotypes currently represent the most effective long term solution to control RWA infestations; however resistance breaking aphid biotypes are rapidly overcoming the incorporated resistance genes under field conditions (Burd et al., 2006; Jankielsohn, 2011). Understanding the molecular basis of plant resistance to the RWA is crucial in creating cultivars with durable resistance (Botha et al., 2005).
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Genetics and Quantitative Trait Loci Mapping of Septoria Tritici Blotch Resistance, Agronomic, and Quality Traits in WheatHarilal, Vibin Eranezhath January 2013 (has links)
Most breeding programs aim at developing superior germplasm and better cultivars that combine high yield, disease and pest resistance, and end-use quality to satisfy the requirements of the growers as well as industry. A population, consisting of 138 F2-8 recombinant inbred lines (RILs) derived from a cross between ‘Steele-ND’ and ND 735, was evaluated to study the inheritance pattern of the septoria tritici blotch (STB)-resistant genes, agronomic and quality traits. The framework map made of 392 markers, including 28 simple sequence repeat (SSR) markers and 364 DArT markers, spanned a total distance of 1789.3 cM and consisted of 17 linkage groups. The map position of quantitative trait loci (QTL) found in this study coincided with the map position of durable STB resistance genes, Stb1. Thirteen QTL were detected for agronomic and quality traits. More saturation of the current map is needed to explore more QTL for this population.
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Genetic mapping of adult plant stripe rust resistance in the wheat cultivar KariegaRamburan, Viresh Premraj 04 1900 (has links)
Thesis (PhD (Agric)) -- Stellenbosch University, 2003. / ENGLISH ABSTRACT: Stripe (yellow) rust of wheat, caused by Puccinia striiformis f.sp. tritici, was first detected as a
single introduction into South Africa in 1996. Two additional pathotypes have since been
identified. Control of the disease may be achieved by use of genetic adult plant resistance
(APR) as is present in the local cultivar 'Kariega'. The aim of this project was to understand the
genetic basis of the APR in 'Kariega' to facilitate breeding of new varieties with genetic
resistance to stripe rust.
A partial linkage map of a 'Kariega X Avocet S' doubled haploid population covering all 21
wheat chromosomes was generated using 208 DNA markers, viz, 62 SSR, 133 AFLP, 3 RGA
and 10 SRAP markers, and 4 alternative loci. The different marker techniques detected varying
polymorphism, viz, overall SSR: 46%, AFLP: 7%, SRAP: 6% and RGA: 9%, and the markers
produced low levels of missing data (4%) and segregation distortion (5%). A significant feature
of the linkage map was the low polymorphism found in the D genome, viz, 19% of all mapped
DNA markers, 11% of all AFLP markers and 30% of the total genome map distance. A region
exhibiting significant segregation distortion was mapped to chromosome 4A and a seedling
resistance gene for stem rust (Puccinia graminis f.sp . tritici), Sr26, mapped to chromosome 6A
close to three SSR markers. The leaf tip necrosis gene, Ltn, which was also segregating in the
population, mapped to chromosome 7D. Protocols for SRAP and RGA were optimised, and
SRAP marker use in wheat genetic linkage studies is reported for the first time.
The linkage map was used together with growth chamber and replicated field disease scores for
QTL mapping. Chromosomes showing statistically significant QTL effects were then targeted
with supplementary SSR markers for higher resolution mapping. The quality of disease
resistance phenotypic data was confirmed by correlation analysis between the different scorers
for reaction type (0.799±0.023) and for transformed percentage leaf area infected
(0.942±0.007).
Major QTL were consistently identified on chromosome 7D (explaining some 25-48% of the
variation) and on chromosome 2B (21-46%) using transformed percentage leaf area infected and transformed reaction type scores (early and final) with interval mapping and modified
interval mapping techniques. Both chromosomal regions have previously been identified in
other studies and the 7D QTL is thought likely to be the previously mapped APR gene Yr 18.
Minor QTL were identified on chromosomes lA and 4A with the QTL on 4A being more
prominent at the early field scoring for both score types. A QTL evidently originating from
'Avocet S' was detected under growth chamber conditions but was not detected in the field,
suggesting genotype-environment interaction and highlighting the need for modifications of
growth chamber conditions to better simulate conditions in the field.
The genetic basis of the APR to stripe rust exhibited by 'Kariega' was established by mapping
of QTL controlling this trait. The linkage map constructed will be a valuable resource for
future genetic studies and provides a facility for mapping other polymorphic traits in the
parents of this population with a considerable saving in costs. / AFRIKAANSE OPSOMMING: Streep of geelroes van koring word veroorsaak deur Puccinia striiformis f. sp tritici, en is die
eerste keer in 1996 in Suid-Afrika na introduksie van 'n enkele patotipe waargeneem. Twee
verdere patotipes is sedertdien in Suid-Afrika gei"dentifiseer. Beheer van die siekte word veral
moontlik gemaak deur die gebruik van genetiese volwasseplantweerstand soos gei"dentifiseer in
die plaaslike kultivar 'Kariega'. Die doel van hierdie studie was om die genetiese grondslag van
die streeproesweerstand te ontrafel ten einde die teling van nuwe bestande kultivars moontlik te
maak.
'n Verdubbelde haplo1ede populasie uit die kruising 'Kariega X Avocet S' is aangewend om 'n
gedeeltelike koppelingskaart vir die volle stel van 21 koring chromosome saam te stel. Die kaart
het uit 208 DNA merkers, nl., 62 SSR, 133 AFLP, 3 RGA, 10 SRAP merkers en 4 ander lokusse
bestaan. Totale polimorfisme wat deur die verskillende merkersisteme opgespoor is, was as volg:
SSR: 46%, RGA: 9%, AFLP: 7% en SRAP: 6%. Die mate van ontbrekende data was gering
(4%) asook die mate van segregasie distorsie (5%) van 'n enkele geval wat op chromosoom 4A
gekarteer is. 'n Prominente kenmerk van die koppelingskaart is die relatiewe gebrek aan
polimorfiese merkers op die D-genoom, nl., slegs 19% van alle DNA merkers en 11% van alle
AFLP merkers wat slegs 30% van die totale genoom kaartafstand bestaan het. Die stamroes
(Puccinia graminis f. sp. tritici) saailingweerstandsgeen, Sr26, karteer op chromosoom 6A naby
drie SSR merkers. Die geen vir blaartipnekrose, Ltn, karteer op chromosoom 7D. Protokolle vir
SRAP en RGA merkers is ge-optimiseer en gebruik van SRAP merkers in koppelings-analise
word vir die eerste keer in koring gerapporteer.
Die koppelingskaart is in kombinasie met groeikamerdata en gerepliseerde veldproefdata gebruik
om die gene (QTL) vir volwasseplant streeproesweerstand te karteer. Chromosome met statisties
betekenisvolle QTL is met aanvullende SSR merkers geteiken om die resolusie van kartering
verder te verhoog. Die kwaliteit van fenotipiese data, soos in die proewe aangeteken, is bevestig
deur korrelasies te bereken tussen lesings geneem deur onafhanklike plantpataloe (0.799 ± 0.023
vir reaksietipe en 0.942 ± 0.007 vir getransformeerde persentasie blaaroppervlakte besmet).
Hoofeffek QTL vir die twee maatstawwe van weerstand is deur middel van die metodes van
interval QTL kartering en gemodifiseerde interval QTL kartering konsekwent op chromosome
7D (25-48% van variasie verklaar) en 2B (21-46% van variasie verklaar) ge"identifiseer. In
vorige studies is aangetoon dat beide chromosome 7D en 2B QTL vir volwasseplant
streeproesweerstand dra. Die 7D QTL is waarskynlik die weerstandsgeen, Yr 18. QTL met klein
effekte op weerstand is op chromosome lA en 4A ge"identifiseer. Die effek van laasgenoemde
geen was meer prominent in die velddata in die vroee datum van weerstandsbeoordeling. Een
QTL, afkomstig van 'Avocet S', is slegs onder groeikamertoestande identifiseerbaar. Dit dui op
moontlike genotipe-omgewing wisselwerking en beklemtoon die noodsaaklikheid om
aanpassings te maak in groeikamertoestande vir beter simulasie van veldproeftoestande.
Die genetiese grondslag van volwasseplantweerstand teen streeproes in die kultivar 'Kariega' is
deur QTL kartering bepaal. Die 'Kariega X Avocet S' koppelingskaart kan as 'n waardevolle basis
dien vir toekomstige genetiese ontledings van ander polimorfiese kenmerke in die populasie.
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Mapping and survey sequencing of Dn resistance genes in Triticum aestivum L.Bierman, Anandi 03 1900 (has links)
Thesis (PhD)--Stellenbosch University, 2015 / ENGLISH ABSTRACT : Diuraphis noxia Kurdjumov (Russian Wheat Aphid; RWA) is a pest of wheat and barley that has spread from its home range in the fertile crescent to most wheat producing countries except Australia. Since its first introduction to South Africa and the USA in the late 20th century, breeding programs for wheat phenotypes
resistant to the aphid were put in place. Conventional breeding practices rely on phenotypic screening to verify traits carried by offspring and genetic tools such as marker assisted selection (MAS) have greatly aided this process in speed and accuracy. The size and complexity of the wheat genome, its allopolyploid nature and repetitive elements have, however, posed a challenge to studies on the genetics of this cereal crop. Many studies have focused on chromosome 3B which is the largest of the wheat chromosomes and easily separated from the redundant genomic background by techniques such as flow cytometry. The similarity in size of the remaining chromosomes however, limits the application of flow cytometry to their isolation. Databases such as Grain-Genes (http://wheat.pw.usda.gov/GG2/index.shtml) house marker data from various mapping studies for all wheat chromosomes and in 2014 the International Wheat Genome Sequencing Consortium (IWGSC) completed the draft genome sequence of wheat categorized by chromosome. Sources of resistance (Dn resistance genes) against RWA are located on chromosome 7D. but despite the marker and sequence data available currently, mapping studies specific for the Dn resistance genes are few. Additionally, sequence data available is derived from cultivars susceptible to RWA and is not comprehensively annotated and assembled in many cases. In this study, we demonstrate a novel, combined approach to isolate and characterize the Dn resistance genes through the use of a genetic map constructed from Amplified Fragment Length Polymorphism (AFLP), Expressed Sequence Tag (EST) and microsatellite markers and a physical map constructed from Next Generation
Sequencing (NGS) data of ditelosomic chromosomes (7DS and 7DL) isolated by microdissection on the PALM microbeam system. A 122.8 cM genetic map was produced from 38 polymorphic AFLP markers and two ESTs with the microsatellite Xgwm111 as anchor to related genetic maps. Through comparison to maps available on GrainGenes the location of the Dn1 resistance gene was narrowed down to a deletion bin (7DS5-0.36-0.62) on the short arm of chromosome 7D with an AFLP marker (E-ACT/M-CTG_0270.84) mapping closely at 3.5 cM and two ESTs mapping at 15.3 cM and 15.9 cM from Dn1. Isolation of individual chromosome arms 7DS and 7DL using the PALM Microbeam system
allowed sequencing of the chromosome without the redundancy of the remainder
of the hexaploid genome. Through isolating the chromosome arms in this way, a >80-fold reduction in genome size was achieved as well as a major reduction in repetitive elements. Analysis of the sequencing data confirmed that 7DL is the physically shorter arm of the chromosome though it contains the majority of protein coding sequences. / AFRIKAANSE OPSOMMING : Diuraphis noxia Kurdjumov (Russiese koring-luis; RWA) is « pes wat op koring en gars voorkom. Die pes het vanaf sy tuiste in die midde Ooste na meeste koringproduserende lande behalwe Australië versprei. Sedert die eerste bekendstelling van RWA in Suid Afrika en die VSA in die vroeë 20ste eeu is teelprogramme
ten gunste van koring lyne met weerstand teen RWA begin. Tradisionele teelprogramme maak op fisieise observasie van die fenotipe staat om te verifieer of plante in die nageslag die gewenste eienskap dra. Genetiese metodes soos merkerondersteunde
seleksie (MAS) versnel hierdie selekteringsproses grootliks. Die grootte en kompleksiteit van die koring genoom asook die polyploïde en herhalende natuur
daarvan is « groot hindernis vir genetiese studies van hierdie graangewas. Baie studies het op chromosoom 3B gefokus wat die grootste van die koring chromosome
is en dus maklik vanaf die res van die oorbodige genomiese agtergond deur tegnieke soos vloeisitometrie geskei word. Die ooreenkoms in grootte tussen die res
van die chromosome bemoeilik die toepassing van vloeisitometrie om hulle te isoleer. Databasisse soos GrainGenes (http://wheat.pw.usda.gov/GG2/index.shtml)
bevat merker data vanaf verskeie karterings-studies vir al die chromosome en in 2014 het die "International Wheat Genome Sequencing Consortium"(IWGSC) die
voorlopige basispaarvolgorde van die koring genoom bekendgestel, gekategoriseer volgens chromosoom. Weerstandsbronne (Dn weerstandsgene) teen RWA kom
meestal op chromosoom 7D voor. Ten spyte van merker en basispaarvolgorde data tans beskikbaar is karterings-studies spesifiek tot die Dn gene skaars en basispaarvolgorde data is vanaf kultivars afkomstig wat nie weerstandbiedend teen RWA is nie en waarvan die annotasie en samestelling baie keer nie goed is nie. In hierdie studie demonstreer ons « nuwe, gekombineerde aanslag om die Dn weerstandsgene te isoleer en karakteriseer deur van « genetiese kaart opgestel met "Amplified Fragment Length Polymorphism"(AFLP), "Expressed Sequence Tag"(EST) en mikrosatelliet
merkers asook « fisiese kaart saamgestel deur die volgende-generasiebasispaarvolgordebepaling
van ditelosomiese chromosome (7DS en 7DL) geïsoleer
deur mikrodisseksie met die "PALM Microbeam"sisteem gebruik te maak. « Genetiese kaart van 122.8 cM was met 38 polimorfiese AFLP merkers en twee EST
merkers geskep. Die mikrosatelliet, Xgwm111, is ook ingesluit en het as anker vir verwante genetiese-kaarte gedien. Deur vergelyking met genetiese-kaarte op
GrainGenes is die posisie van die Dn1 weerstandsgeen vernou na « delesie bin (7DS5-0.36-0.62) op die kort arm van chromosoom 7D met « AFLP merker (EACT/
M-CTG_0270.84) wat ongeveer 3.5 cM vanaf die geen karteer. Die twee EST merkers is 15.3 cM en 15.9 cM vanaf die geen gekarteer. Isolering van die individuele
chromosoom arms, 7DS en 7DL, deur van die "PALM Microbeam"sisteem gebruik te maak het basispaarvolgordebepaling van die chromosoom toegelaat sonder die oortolligheid van die res van die hexaploïde genoom. Deur die chromosoom so te isoleer is « >80-maal verkleining in genoom grootte bereik insluitend « groot reduksie in herhalende elemente. Analise van die data vanaf basispaarvolgordebepaling
het bevestig dat chromosoom 7D die fisiese kleiner chromosoom is maar dat dit die meerderheid van proteïn koderende basispaarvolgordes bevat.
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A study of resistance to cereal cyst nematode (`Heterodera avenae Woll.`) located in the rye genome of triticale / by Robert AsieduAsiedu, Robert January 1986 (has links)
Bibliography: leaves 133-152 / iv, 152 leaves, [47] leaves of plates : ill. (1 col.) ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Thesis (Ph.D.)--University of Adelaide, 1987
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Mapping of chromosome arm 7DL of Triticum aestivum L.Heyns, I.C. 03 1900 (has links)
Thesis (MSc (Genetics))--University of Stellenbosch, 2005. / The Russian wheat aphid, Diuraphis noxia (Mordvilko), is a serious insect pest of wheat and
barley. It affects the quality and yield of grain by sucking plant sap from the newest growth
whilst toxic substances are injected that destroy plant tissue. The Russian wheat aphid also
acts as a vector of plant viruses. The cultivation of aphid resistant cultivars is the preferred
control strategy and nine resistance genes, designated Dn1 to Dn9, have been identified.
Another undesignated gene, Dnx, was found in the wheat accession PI220127. Mapping of the
resistance genes relative to known markers will improve their use in breeding programs.
The dominant RWA resistance gene, Dn5, was identified in the accession PI294994
and mapped to chromosome arm 7DL. However, recent reports have placed Dn5 on ...
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Mapping genes for stem rust and Russian wheat aphid resistance in bread wheat (Triticum aestivum)Wessels, Willem Gerhardus 03 1900 (has links)
Thesis ( MScAgric) -- Stellenbosch University, 1997. / ENGLISH ABSTRACT: Stem rust is considered the most damaging of the wheat rusts causing yield losses of more than
50% in epidemic years. Similarly, Russian wheat aphids (RWA) can be regarded as one ofthe
most devastating insect pests of wheat. Yield losses due to R W A primarily result from a
reduction in plant resources (sucking plant sap). Secondary losses are incurred by viruses
transmitted during feeding. Mapping disease and insect resistance genes that are effective against
prevailing pathotypes and biotypes of South Africa will optimize their utilization in breeding
programmes.
The wheat line, 87M66-2-l, is homozygous for a single dominant stem rust resistance gene
located on chromosome lD. This stem rust resistance gene has been derived from Triticum
tauschii accession RL5289 and is here referred to as Srtau. The aim of this study was to
determine the chromosome arm involved. Following the chromosome arm allocation of Srtau,
its possible linkage with the genes Rg2, Lr 21 , Sr X and Sr 33 was studied.
A telosomic analysis has shown that Srtau is located on chromosome arm 1 DS and is linked to
the centromere with a recombination frequency of 21 ± 3 .40%. Glume blotch and a heavy
mildew infection of segregating families planted in the field in 1996 made the linkage study
between Lr 21 (leaf rust resistance) and Rg2 (glume colour) impossible. However, estimated
linkages of 9 ± 1.9 map units between Sr33 (stem rust resistance) and Srtau, ± 6 map units
between Sr X (stem rust resistance) and Sr 3 3 and ± 1 0 map units between Sr X and Srtau suggested
that SrX, Sr33 and Srtau are closely linked on I DS. Taking existing map data into consideration,
it seems that the most likely order of the genes is: centromere - Srtau - Sr 3 3 - Sr X.
A single dominant R W A resistance gene, Dn5, was identified in the T aestivum accession 'SA
463' and is located on chromosome 7D. The aim ofthis study was to determine the chromosome
arm involved. The possible linkage of Dn5 with the endopeptidase locus, Ep-D1 b. and chlorina
mutant gene, cn-D1, was then studied. Endopeptidase zymograms of 'SA 463' revealed two
unknown polymorphisms. F 2 monosomic analyses involving the chromosomes 7 A, 7B and 7D
were performed in an attempt to identify the loci associated with these polymorphisms.
Dn5 was mapped on chromosome arm 7DL. A recombination frequency of60 ± 4.53% between
Dn5 and the centromere suggested the absence of linkage. Linkage between Ep-Dl and cn-Dl
could not be calculated as a result of similar isoelectric points of the 7DL encoded endopeptidases
of the parental material studied. Recombination frequencies of32 ± 4.97% between Dn5 and EpDl
and 37 ± 6.30% between Dn5 and cn-Dl were, however, encountered. The two novel
endopeptidase alleles encountered in 'SA 463' were designated as Ep-Dle and Ep-Ald.
A RWA resistance gene was transferred from the rye accession ' Turkey 77' to wheat and in the
process the RWA resistant wheat lines 91M37-7 and 91M37-51 were derived. No rye chromatin
could be detected in these plants following C-banding. The aim of this study was to determine
(i) on which chromosome the gene(s) is located, and (ii) whether the resistance can be the result
of a small intercalary translocation of rye chromatin.
A monosomic analysis of the RWA resistance gene in 91M37-51 has shown that a single
dominant resistance gene occurs on chromosome 7D. The use of rye-specific dispersed probes
did not reveal any polymorphisms between the negative controls and RW A resistant lines 91M3 7-
7 and 91M37-51 which would suggest that it is unlikely that the resistance was derived from rye. / AFRIKAANSE OPSOMMING: Stamroes word as die mees vemietigende graanroessiekte beskou en het in epidemiese jare
oesverliese van meer as 50% tot gevolg. Russiese koringluise is eweneens een van die emstigste
insekplae van koring. Russiese koringluise veroorsaak oesverliese deurdat dit plantsap uitsuig
en die plant van voedingstowwe beroof. Dit tree egter ook as 'n virusvektor op en kan so
indirekte oesverliese veroorsaak. Kartering van siekte- en insekweerstandsgene wat effektief is
teen die Suid-Afrikaanse patotipes en biotipes, sal hulle gebruik in teelprogramme optimiseer.
Die koringlyn, 87M66-2-l , is homosigoties vir 'n dominante stamroes-weerstandsgeen wat op
chromosoom ID voorkom. Hierdie weerstandsgeen is uit die Triticum tauschii aanwins, RL5289,
afkomstig en word hiema verwys as Srtau. Daar is gepoog om te bepaal op watter chromosoomarm
Srtau voorkom, waama sy koppeling met betrekking tot die gene Rg2, Lr21 , SrX en Sr33
bepaal is.
'n Telosoomanalise het getoon dat Srtau op chromosoom-arm 1 DS voorkom en gekoppel is aan
die sentromeer met 'n rekombinasie-frekwensie van 21 ± 3.40%. Segregerende populasies wat
in 1996 in die land geplant is, is hewig deur aarvlek en poeieragtige meeldou besmet en dit het
die moontlike bepaling van koppeling tussen Lr21 (blaarroesweerstand) en Rg2 (aarkaffie kleur)
belemmer. Koppelingsafstande van 9 ± 1. 9 kaart-eenhede tussen Sr 33 (stamroesweerstand) en
Srt au, ± 6 kaart -eenhede tussen Sr X ( stamroesweerstand) en Sr 3 3 en ± 1 0 kaart -eenhede tussen
SrX en Srtau is geraam en toon dat SrX, Sr33 en Srtau nou gekoppel is. Die waarskynlikste
volgorde van die gene op lDS is: sentromeer- Srtau- Sr33- SrX.
'n Enkele dominante Russiese koringluis-weerstandsgeen, Dn5, is in dieT aestivum aanwins 'SA
463 ' ge"identifiseer en kom op chromosoom 7D voor. Die studie het ten doel gehad om te bepaal
op watter chromosoom-arm Dn5 voorkom, asook wat die koppeling van Dn5 met die
endopeptidase lokus, Ep-Dl, en die chlorina mutante geen, cn-Dl , is. Endopeptidase
simograrnme van 'SA 463' het twee onbekende polimorfismes getoon. Die gene wat kodeer vir
hierdie twee polimorfismes is met behulp van F2 monosoom-analises wat die chromosome 7 A,
7B en 7D betrek, gei:dentifiseer.
Dn5 is op chromosoom 7DL gekarteer. 'n Rekombinasie-frekwensie van 60 ± 4.53% is gevind
vir die sentromeer en Dn5 en dui op die afwesigheid van koppeling. Koppeling tussen Ep-Dl en
cn-Dl kon nie bepaal word nie omdat die endopeptidase bande geproduseer deur die ouerlike
materiaal wat in die studie gebruik is, nie met sekerheid in die nageslag onderskei kon word nie.
Rekombinasie-frekwensies van 32 ± 4.97% tussen Dn5 en Ep-Dl en 37 ± 6.30% tussen Dn5 en
cn-Dl is egter bereken. Dit word voorgestel dat daar na die twee onbekende endopeptidase-allele
wat in 'SA 463 ' voorkom, verwys word as Ep-Dle en Ep-Ald.
'n Russiese koringluis-weerstandsgeen is uit die rog-aanwins, 'Turkey 77', oorgedra na koring
en in die proses is die Russies koringluis weerstandbiedende lyne, 91M37-7 en 91M37-51 ,
geproduseer. Geen rog-chromatien kon egter met behulp van C-bande in hierdie lyne
waargeneem word nie. Die doel van die studie was om te bepaal (i) op watter chromosoom die
geen(e) voorkom, en (ii), of die Russiese koringluis weerstandsgeen die gevolg kan wees van 'n
klein interkalere translokasie van rog- chromatien.
'n Monosoom-analise van die Russiese koringluis-weerstandsgeen in 91M37-51 het getoon dat
'n enkele dominante weerstandsgeen op chromosoom 7D voorkom. Rog-spesifieke herhalende
peilers het geen polimorfismes tussen negatiewe kontroles en die Russiese koringluis
weerstandbiedende lyne 91M37-7 en 91M37-51 getoon nie. Dit is dus onwaarskynlik dat die
weerstand in die lyne uit rog verhaal is.
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Profiling of gene expression in bread wheat (Triticum aestivum L.) line PI 137739 in response to Russian wheat aphid (Diuraphis noxia Mordvilco) feedingLacock, Lynelle 09 May 2005 (has links)
This thesis investigates the effect of Russian wheat aphid (RWA; Diuraphis noxia) infestation on the defence responses of the bread wheat line, PI 137739, on a molecular level. PI 137739 is known to contain the RWA resistance gene, Dn1. The study was conducted by utilising and combining a vast array of molecular biological techniques. Chapter 1 introduces the reader to a summary of the resistance responses observed within infested plants. A detailed description of the Russian wheat aphid follows and the genes responsible for RWA resistance in wheat is discussed. A brief report of research performed on the bread wheat genome is given and the biochemical defence responses of plants against insect infestation are discussed. This is followed by a concise description of resistance (R) genes and resistance gene categories in plants. The last discussion concerns microarray technology, a molecular tool utilised during this study. Chapter 2 aims at identifying genes involved in resistance against RWA infestation; specifically, genes containing the conserved nucleotide binding site¬leucine rich repeat (NBS-LRR) motif. Genomic, as well as complementary DNA (cDNA), was utilised in order to compare functional gene expression in wheat infested with the RWA. This was executed by employing PCR-based methods, single-pass sequencing and basic local alignment search tool (BLAST) analyses. Chapter 3 introduces suppression subtractive hybridisation (SSH) as a tool to further identify NBS-LRR or other resistance-related sequences in RWA infested wheat plants. SSH allows the comparative analysis of differential gene expression in RWA infested and uninfested wheat in order to identify resistance-¬related genes expressed in the infested, resistant wheat plants. The effect of RWA infestation on wheat resistance responses was examined further in chapter 4 through microarray analysis. The aim was the introduction and establishment of the microarray technique and to test the feasibility of using microarrays for differential gene expression and regulation studies. Microarray slides were assembled in order to monitor the up- and down¬regulation of genes at different time intervals - day 2, day 5 and day 8 - of RWA infestation. Clones isolated throughout this study were assembled on microarray slides and probed with control and RWA infested RNA. Differential gene regulation was assessed and further confirmed through Northern blot analyses, as well as quantitative real-time PCR. The thesis concludes with a general summary of the results obtained in chapter 5 and future prospects are outlined. / Thesis (PhD(Genetics))--University of Pretoria, 2005. / Genetics / unrestricted
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Evaluation and genetic analysis of wheat streak mosaic virus resistance in wheat germplasm by symptomatology, enzyme-linked immunosorbent assay, and slot-blot hybridizationStoddard, Sara L. January 1986 (has links)
Call number: LD2668 .T4 1986 S76 / Master of Science / Plant Pathology
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Ontwikkeling van molekulere merkers vir wilde-spesie-verhaalde weerstandsgeenkomplekse van gewone koringEksteen, Aletta 03 1900 (has links)
Thesis (MSc (Genetics))--University of Stellenbosch, 2009. / Worldwide, the rust diseases cause significant annual wheat yield losses (Wallwork 1992; Chrispeels & Sadava 1994). The utilization of host plant resistance to reduce such losses is of great importance particularly because biological control avoids the negative environmental impact of agricultural chemicals (Dedryver et al. 1996). The wild relatives of wheat are a ready source of genes for resistance to disease and insect pests. A large degree of gene synteny still exists among wheat and its wild relatives (Newbury & Paterson 2003). It is therefore possible to transfer a chromosome segment containing useful genes to a homologous region in the recipient genome without serious disruption of genetic information. Special cytogenetic techniques are employed to transfer genes from the wild relatives to the wheat genomes (Knott 1989). Unfortunately the transfer of useful genes may be accompanied by the simultaneous transfer of undesirable genes or redundant species chromatin which has to be mapped and removed (Feuillet et al. 2007). DNA markers are extremely useful for the characterisation and shortening of introgressed regions containing genes of interest (Ranade et al. 2001), and may also be used for marker aided selection of the resistance when the genes are employed commercially. Eight wheat lines containing translocations/introgressions of wild species-derived resistance genes were developed by the Department of Genetics (SU). These lines are presently being characterized and mapped and attempts are also being made to shorten the respective translocations. This study aimed to find DNA markers for the various translocations and to convert these into more reliable SCAR markers that can be used in continued attempts to characterize and improve the respective resistance sources.
A total of 260 RAPD and 21 RGAP primers were used to screen the eight translocations and, with the exception of Lr19, it was possible to identify polymorpic bands associated with each translocation. However, it was not possible to convert all of these into more reliable SCAR markers. The primary reason for this was the low repeatability of most of the bands. Certain marker fragments turned out to be repeatable but could not be converted successfully. Some of the latter can, however, be used directly (in RAPD or RGAP reactions) as markers. The Lr19 translocation used in the study (Lr19-149-299) is a significantly reduced version of the original translocation and failure to identify polymorphisms associated with it can probably be ascribed to its small size. The following numbers of markers (direct and converted into SCARs) were Worldwide, the rust diseases cause significant annual wheat yield losses (Wallwork 1992; Chrispeels & Sadava 1994). The utilization of host plant resistance to reduce such losses is of great importance particularly because biological control avoids the negative environmental impact of agricultural chemicals (Dedryver et al. 1996). The wild relatives of wheat are a ready source of genes for resistance to disease and insect pests. A large degree of gene synteny still exists among wheat and its wild relatives (Newbury & Paterson 2003). It is therefore possible to transfer a chromosome segment containing useful genes to a homologous region in the recipient genome without serious disruption of genetic information. Special cytogenetic techniques are employed to transfer genes from the wild relatives to the wheat genomes (Knott 1989). Unfortunately the transfer of useful genes may be accompanied by the simultaneous transfer of undesirable genes or redundant species chromatin which has to be mapped and removed (Feuillet et al. 2007). DNA markers are extremely useful for the characterisation and shortening of introgressed regions containing genes of interest (Ranade et al. 2001), and may also be used for marker aided selection of the resistance when the genes are employed commercially. Eight wheat lines containing translocations/introgressions of wild species-derived resistance genes were developed by the Department of Genetics (SU). These lines are presently being characterized and mapped and attempts are also being made to shorten the respective translocations. This study aimed to find DNA markers for the various translocations and to convert these into more reliable SCAR markers that can be used in continued attempts to characterize and improve the respective resistance sources.
A total of 260 RAPD and 21 RGAP primers were used to screen the eight translocations and, with the exception of Lr19, it was possible to identify polymorpic bands associated with each translocation. However, it was not possible to convert all of these into more reliable SCAR markers. The primary reason for this was the low repeatability of most of the bands. Certain marker fragments turned out to be repeatable but could not be converted successfully. Some of the latter can, however, be used directly (in RAPD or RGAP reactions) as markers. The Lr19 translocation used in the study (Lr19-149-299) is a significantly reduced version of the original translocation and failure to identify polymorphisms associated with it can probably be ascribed to its small size. The following numbers of markers (direct and converted into SCARs) were
v
identified: S8-introgression (Triticum dicoccoides) = one RAPD and two SCARs; S13-translocation (Aegilops speltoides) = four RAPDs, three RGAPs and five SCARs; S15-translocation (Ae. peregrina) = one RAPD and two SCARs; S20-translocation (Ae. neglecta) = two RAPDs, two RGAPs and one SCAR. The markers are already being employed in current projects aiming to map and shorten these translocations. Some of the markers can be combined in multiplex reactions for more effective mass screening. No repeatable markers could be identified for the four remaining translocations (S12 from Ae. sharonensis; S14 from Ae. kotschyi; Smac from Ae. biuncialis and Lr19-149-299 from Thinopyrum ponticum).
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