Thesis (MSc (Genetics))--Stellenbosch University, 2008.

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.

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

Call number: LD2668 .T4 1986 S76 / Master of Science / Plant Pathology

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).

Thesis (MSc (Genetics))--University of Stellenbosch, 2010. / Includes bibliography. / ENGLISH ABSTRACT: Wheat rust is a significant contributor to the total impact of diseases on sustainable wheat production. Genetic resistance, produced by using resistance genes from wheat and other related wild species, is the simplest and most cost-effective way to guard against these diseases. The pyramiding of resistance genes in a single line is a vital practice in bringing about durable resistance. This study aimed to develop a series of doubled haploid (DH) wheat lines containing combination's of wild species genes for rust resistance. Rust resistance genes Lr19 (7BL), Sr31/Lr26/Yr9/Pm8 (1BS) and Lr54/Yr37 (2DL) were combined by means of crossing. Breeders. lines which have complex resistance including Lr24/Sr24 (3DL), Lr34/Yr18 (7D), Sr36 (2BS) and Sr2 (3BS), were used. Marker assisted selection (MAS) was used to type populations for the above mentioned genes. Using the DH method (maize pollination technique), an inbred population was developed from the selected lines, after which the lines were characterised molecularly for the resistance gene translocations which they contain. The study produced 27 lines with diverse genetic profiles. Seven lines contain four translocations (Lr24/Sr24, Lr34/Yr18, Sr2 and Lr19 or Sr31) each, 11 lines contain three genes each, six lines contain two genes each and only three lines contain a single translocation (Lr24/Sr24). The reality that rust pathogens have already overcome three of the resistance genes in the final population . Lr19, Sr31 and Sr24 . is a clear indication of the value of using non-major gene resistance for bringing about durable resistance. The focus should fall ever more greatly upon the application of quantitative trait loci (QTL) for this purpose, which will result in MAS contributing to the development of more durable resistance. The value of the integration of MAS and DH in combination with conventional breeding practices in breeding programmes has already been illustrated internationally for increasing the rate of cultivar development and this is reaffirmed by this study. / AFRIKAANSE OPSOMMING: Koringroes lewer jaarliks .n beduidende bydrae tot die totale impak van siektes wat volhoubare koringverbouing belemmer. Die mees eenvoudige en koste-effektiewe verweer teen hierdie siektes is genetiese weerstand, wat deur weerstandsgene vanaf koring, sowel as wilde verwante spesies, bewerkstellig word. Die stapeling van weerstandsgene in .n enkele lyn word as .n onontbeerlike praktyk om duursame weerstand tot stand te bring, geag. Hierdie studie het ten doel gehad om .n reeks verdubbelde haploiede (VH) koringlyne te ontwikkel wat kombinasies van wilde spesie gene vir roesweerstand bevat. Roesweerstandsgene Lr19 (7BL), Sr31/Lr26/Yr9/Pm8 (1BS) en Lr54/Yr37 (2DL) is deur middel van kruisings gekombineer. Telerslyne wat oor komplekse weerstand beskik wat Lr24/Sr24 (3DL), Lr34/Yr18 (7D), Sr36 (2BS) en Sr2 (3BS) insluit, is gebruik. Merker-bemiddelde seleksie (MBS) is gebruik om populasies vir bogenoemde gene te tipeer. .n Ingeteelde populasie is vanaf die geselekteerde lyne met behulp van die VH metode (mielie-bestuiwing tegniek) ontwikkel, waarna die lyne molekuler vir die weerstandsgeentranslokasies waaroor hul beskik, gekarakteriseer is. Die studie het 27 lyne met diverse genetiese profiele opgelewer. Sewe lyne bevat vier weerstandsgeentranslokasies (Lr24/Sr24, Lr34/Yr18, Sr2 en Lr19 of Sr31) elk, 11 lyne beskik oor kombinasies van drie gene elk, ses bevat twee gene elk en slegs drie lyne beskik oor .n enkele translokasie (Lr24/Sr24). Die realiteit dat die roespatogene reeds drie van die weerstandsgene in die finale populasie . Lr19, Sr31 en Sr24 . oorkom het, benadruk die waarde van die gebruik van nie-hoofgeenweerstand vir die daarstelling van duursame weerstand. Die fokus behoort toenemend meer op die aanwending van kwantitatiewe kenmerk-loci (QTL) vir hierdie doel te val en sal sodoende teweegbring dat MBS bydra tot die ontwikkeling van meer duursame weerstand. Die waarde van die integrasie van MBS en VH in kombinasie met konvensionele telingsmetodiek is reeds internasionaal vir die versnelling van kultivarontwikkeling aangetoon en word ook deur hierdie studie herbevestig.

Thesis (MSc.) -- Stellenbosch University, 1997. / ENGLISH ABSTRACT: An octoploid triticale was derived from the F1 of a Russian wheat aphid resistant rye, 'Turkey 77', and 'Chinese Spring' wheat. The alloploid was crossed (a) to common wheat, and (b) to the 'Imperial' rye to 'Chinese Spring' disomic addition lines. F2 progeny from these crosses were tested for Russian wheat aphid resistance and C-banded. Resistance was found to be associated with chromosome arm 1RS of the 'Turkey 77' rye genome. This initial work was done by MARAIS (1991) who made a RWA resistant, monotelosomic 1RS ('Turkey 77') addition plant available for the study. The F3 progeny of this monotelosomic addition plant was used to confirm the RWA resistance on chromosome 1RS. The monotelosomic addition plant was then crossed with the wheat cultivar 'Gamtoos', which has the 1BL.1 RS 'Veery' translocation. Unlike the 1RS segment in 'Gamtoos', the 'Turkey 77'- derived 1RS telosome did not express the rust resistance genes 5r31 and Lr26 which could then be used as markers. From the F1 a monotelosomic 1RS addition plant that was also heterozygous for the 1BL.1 RS translocation, was selected and testcrossed with an aphid susceptible common wheat, 'Inia 66'. Meiotic pairing between the .rye arms resulted in the recovery of five euploid, Russian wheat aphid resistant plants out of a progeny of 99 euploids. One recombinant also retained 5r31 and Lr26 and was allowed to self pollinate. With the aid of SOS-PAGE profiles, Russian wheat aphid resistant 1BL.1 RS translocation homozygotes were identified and it was possible to confirm that the Russian wheat aphid resistance gene was in fact transferred to the 1BL.1RS ('Veery') translocation. Two attempts were made to map the Russiar, wheat aphid locus or loci. (1) Telosomic mapping was attempted. For this purpose a plant with 2n = 40 + 1BL.1 RS + 1RS was obtained, and testcrossed with a Russian wheat aphid susceptible wheat. (2) A disomic, recombined 1BL.1 RS translocation line with Russian wheat aphid resistance but lacking the Lr26 and Sr31 alleles was crossed with 'Gamtoos' and the F1 testcrossed. The testcross in both strategies were done with 'Chinese Spring'. In the first experiment the Sr31 locus was located 10.42 map units from the Lr26 locus. The rust resistance data implied that the genetic distance estimates may be unreliable and therefore the laborious Russian wheat aphid resistance tests were not done. In the second experiment a Russian wheat aphid resistance gene was located 14.5 map units from the Lr26 locus. In the latter cross nonmendel ian segregation of the Russian wheat aphid resistance evidently occurred which implied that the estimated map distance may be inaccurate. It was also not possible to determine the number of genes involved from the data. / Digitized at 300 dpi Colour & b/W PDF format (OCR), using ,KODAK i 1220 PLUS scanner. Digitised, Ricardo Davids on request from ILL 25 April 2013 / AFRIKAANSE OPSOMMING: 'n Oktaplo"lede triticale is gemaak vanaf die F1 van 'n kruising tussen 'n Russiese koringluis-weerstandbiedende rog, 'Turkey 77', en die koringkultivar 'Chinese Spring'. Die alloplo"led is gekruis met gewone broodkoring en met 'Imperial' rog/'Chinese Spring' disomiese addissielyne. Die F2 nageslag vanaf hierdie kruisings is getoets vir Russiese koringluisweerstandbiedendheid en C-bande is ook gedoen. Weerstand is gevind wat geassosieer is met die 1RS chromosoomarm van 'Turkey 77'. Hierdie oorspronklike werk is deur MARAIS (1991) gedoen en uit sy materiaal is 'n monotelosomiese 1RS ('Turkey 77') addissieplant beskikbaar gestel vir die huidige studie. Die F3 nageslag van hierdie monotelosomiese addissieplant is gebruik om die weerstand teen die Russiese koringluis op chromosoom 1RS te bevestig. Die monotelosomiese addissieplant is ook gekruis met die koringkultivar 'Gamtoos' wat die 1BL.1 RS-translokasie dra. Hoewel die 1RS segment van 'Gamtoos' die roesweerstandsgene, Sr31 en Lr26 uitdruk, is dit nie die geval met die 'Turkey 77' 1RS telosoom nie. Hierdie gene kon dus as merkergene gebruik word. Vanuit die F1 is 'n monotelosomiese 1RS addissieplant geselekteer wat ook heterosigoties was vir die 1BL.1 RStranslokasie. Hierdie plant is getoetskruis met 'n luisvatbare gewone broodkoring, 'Inia 66'. Meiotiese paring tussen die rogarms het daartoe gelei dat vyf euplo"lede Russiese koringluis-weerstandbiedende nageslag uit 99 euplo"lede nageslag geselekteer kon word. Een rekombinant het ook Sr31 en Lr26 behou en is toegelaat om self te bestuif. Met behulp van SDSPAGE profiele is Russiese koringluis-weerstandbiedende 1BL.1 RStranslokasie homosigote ge"ldentifiseer en kon bevestig word dat die weerstandsgeen vir die Russiese koringluis oorgedra is na die 1BL.1 RS ('Veery') -translokasie. Twee strategies is gevolg om die Russiese koringluislokus of -loci te karteer: (1) 'n Telosomiese analise is gedoen. 'n Plant met 2n = 40 + 1BL.1 RS + 1RS is verkry en met 'n luisvatbare koring bestuif. (2) 'n Gerekombineerde, disomiese plant met Russiese koringluis-weerstandbiedendheid maar sonder die Lr26 en Sr31 allele is gekruis met 'Gamtoos' en die F1 getoetskruis. Die toetskruisouer in beide die strategiee was 'Chinese Spring'. In die eerste eksperiment is die Sr31-lokus 10.42 kaarteenhede vanaf die Lr26-lokus gelokaliseer. Die raesdata het ge"impliseer dat onbetraubare genetiese kaarteenhede geskat sou word en daarom is die omslagtige Russiese koringluis weerstandsbepalings nie gedoen nie. In die tweede eksperiment is die Russiese koringluis-weerstandsgeen op 14.5 kaarteenhede vanaf die Lr26-lokus gelokaliseer. Nie-Mendeliese segregasie van die Russiese koringluis-weerstand in hierdie karteringseksperiment het ge'impliseer dat die berekende kaartafstand onakkuraat mag wees. Dit was ook nie moontlik om op grand van die data die aantal gene betrakke af te lei nie.

T. aestivum ssp. spelta Iranian type has long been thought to potentially be the direct non-free threshing hexaploid progenitor. I evaluated a RIL population derived from a cross between CS and Iranian spelta accession P503 to identify loci suppressing free-threshabilty in P503. Identification of QTL associated with threshability in region known to harbor the Tg2A gene, and an inactive tg2D allele supported the hypothesis of Iranian spelta being derived from a more recent hybridization between free-threshing hexaploid and emmer wheat. Parastagonospora nodorum is an important fungal pathogen and secretes necrotrophic effectors that evoke cell death. In this research, a DH population segregating for Snn5 was used to saturate Snn5 region of chromosome 4B with molecular markers. The physical distance between Snn5 flanking markers was narrowed to 1.38 Mb with genetic distance of 2.8 cM. The markers developed in this study will provide a strong foundation for map-based cloning of Snn5.