Includes bibliographical references. The thesis aims to characterise the basis of naturally occuring resistance to BYDV in cereals in three ways: i. A map-based approach to the isolation of the Yd2 gene for BYDV resistance from barley. -- ii. Determining if a BYDV resistance gene in rice is orthologous to Yd2. -- iii. Establishing if other BYDV resistance genes in non-Ethiopian barleys are allelic to Yd2.

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

Blackleg is a disease of canola and rapeseed cultivars that is caused by the fungus Leptosphaeria maculans (Desm.) Ces. & de Not., and it is by far the most destructive pathogen of canola in North America. In recent years, blackleg strains belonging to pathogenicity groups (PG) 3 and 4 have been discovered in North Dakota. Recent outbreaks of the disease have added a sense of urgency to characterize the risk these new strains represent for the canola industry and to identify sources of resistance against them. Thus, the objectives of this study were to screen germplasm collections of Brassica rapa, B. napus. and B. juncea for their reaction to PG3 and PG4 and to evaluate the reaction of a sample of currently used canola commercial cultivars grown in North Dakota to PG3 and PG4 as means to estimate the risk these new strains represent. All canola germplasm and commercial cultivars were evaluated in replicated trials in greenhouse conditions using cotyledon bioassays. In 2009 and 2010, the effect of these strains, using five inoculation sequences, on the reaction of canola seedlings was also evaluated. Field trials were not conducted because of the limited geographical distribution of the new strains. No adequate sources of resistance were identified among the 277 B. rapa and 130 B. napus accessions evaluated; however, 22 of the 406 accessions of Brassicajuncea evaluated were considered to have moderate levels of resistance. B. juncea seedlings that survived these inoculations were self-pollinated and their progeny (F1) were also screened. As before, surviving seedlings were self-pollinated. These F2 seeds are the elite materials that could be used in future breeding programs. The complementary study evaluating the role of sequence inoculations in reaction of canola seedlings to blackleg indicated that an increased susceptibility to PG3 occurred when seedlings were first inoculated with PG4; however, reaction to PG4 was not enhanced by a prior inoculation with PG3. All 75 commercial cultivars evaluated were susceptible to PG3 and PG4, indicating that the risk these new strains represent to the canola industry of the region is serious. Further, when a subsample of 16 cultivars were challenged with PG2, they were either resistant or moderately resistant, suggesting the ratings the industry are using relate to reaction of those cultivars to PG2 but not to the new strains; thus, growers should use caution when using these ratings while deciding on which cultivars to plant. / North Dakota State University. Department of Plant Pathology / USDA North Central Canola Research Program / Northern Canola Growers Association

Tan spot, caused by Pyrenophora tritici-repentis (Ptr), is a major foliar disease on wheat. The pathosystem involves three pairs of necrotrophic effector (NE) and host sensitivity (S) gene interactions, namely Ptr ToxA-Tsn1, Ptr ToxB-Tsc2 and Ptr ToxC-Tsc1. Additionally, genetic factors conferring race-nonspecific resistance have been identified. The objectives of this study were to map tan spot resistance QTL and investigate the role of NE-S interactions in disease in durum using association and bi-parental mapping. Evaluation of a worldwide collection of durum accessions allowed identifying highly resistant nineteen lines to multiple Ptr races. Association mapping revealed genomic regions on chromosomes 1A, 2B and 3B significantly associated with resistance to tan spot, which likely correspond to Tsc1, Tsc2 and racenonspecific resistance. Using a bi-parental population derived from Ben and PI 41025, we found that ToxA-Tsn1 interaction plays no significant role in disease, instead a major race-nonspecific QTL on chromosome 5A was identified.

Thesis (PhD (Genetics))--University of Stellenbosch, 2010. / Includes bibliography. / ENGLISH ABSTRACT: The wild relatives are an important source of new genes for the genetic improvement of wheat. At Stellenbosch University the leaf and stripe rust resistance genes Lr54 and Yr37 were transferred from Aegilops kotschyi to chromosome 2DL of wheat. In an attempt to reduce the size of the whole-arm translocation on which the resistance genes occur, homoeologous pairing was induced between the wheat and corresponding Ae. kotschyi chromatin. The purpose of this study was to: (i) Evaluate the testcross progeny thus obtained; identify translocation recombinants that retained Lr54/Yr37 and to characterize these using molecular markers (ii) Test for the presence of genes for photoperiod insensitivity (Ppd) and reduced height (Rht) believed to be associated with the translocation (iii) Develop a SCAR marker for the most useful recombinant that could be recovered. Ten putative translocation recombinants were identified following the screening of 159 hemizygous testcross F1 plants with three microsatellite markers specific for chromosome arm 2DL. The recombinants were then characterized with another five microsatellite markers. Using the eight microsatellite markers the recombinants were ordered in two size categories with recombinant #74 being the shortest and having retained only proximal alien chromatin on 2DL. In addition to microsatellite markers, RAPDs, RGAs, AFLPs and SCAR markers were genetically mapped to the translocation and further resolved the recombinants into three size categories. In an attempt to find suitable markers linked to the shortest recombinant (#74) a polymorphic 410 bp AFLP fragment produced with the enzyme/selective nucleotide combination EcoRI – AAC/MseI – CAT, was converted into a dominant SCAR marker. In addition three microsatellite markers that mapped to recombinant #74 provided a useful recessive molecular marker system to detect Lr54/Yr37. Evaluation of the 10 recombinants with four 2DS-specific microsatellite markers revealed a large deletion of this chromosome arm in recombinant #74. This deletion may affect plant phenotypic characteristics and a strategy to replace the deleted region in recombinant #74 is proposed. To test for the presence of a gene for photoperiod insensitivity on the translocation, translocation-carriers plus controls were subjected to long and short day treatments, and the effect on time to flowering was studied. However, no evidence was found for the presence of such a gene. A height experiment to test for the presence of an Rht gene on the translocation confirmed its presence. This gene (designated H) appeared to be different from Rht8 on chromosome 2DS and was mapped on 2DL. While H does not occur in a chromosome region that corresponds with the location of Rht8, it does not rule out the possibility that they could be orthologous loci. Plant height data obtained for recombinant #74 suggested that H was lost through recombination in this particular recombinant. A greenhouse experiment suggested that the full-length translocation increased 100 kernel mass but had a detrimental effect on overall plant yield. Since a much shorter recombinant (#74) has been obtained, this will also have to be evaluated for associated effects. Such an evaluation needs to be done under commercial growing conditions and should involve the comparison of near-isogenic bulks with and without recombinant chromosome #74. The stripe rust resistance gene (Yr37) was mapped by screening hemizygous TF2 progeny of the 10 recombinants with Puccinia striiformis pathotype 6E22A+. Recombinant #74 retained both Lr54 and Yr37 and the two genes therefore occur towards the centromere. / AFRIKAANSE OPSOMMING: Wilde verwante spesies is ‘n belangrike bron van nuwe gene vir die genetiese verbetering van koring. By die Universiteit van Stellenbosch is die blaar-roes en streep-roes weerstandsgene Lr54 en Yr37 vanaf Aegilops kotschyi na chromosoom 2DL van koring oorgedra. ‘n Poging is vervolgens aangewend om die vol-armtranslokasie waarop die weerstandsgene voorkom te verklein deur homoeoloë paring tussen die koring en ooreenstemmende Ae. kotschyi chromatien te induseer. Die doelstelling van hierdie studie was daarom as volg: (a) Evaluering van die verkreë toetskruis-nageslag asook die identifisering en karakterisering van translokasie rekombinante wat Lr54/Yr37 behou het. (b) Toetsing vir fotoperiode onsensitiwiteits- (Ppd) en verkorte plant-hoogte (Rht) gene wat moontlik op die translokasie kon voorkom. (c) Die ontwikkeling van ‘n volgorde-spesifieke polimerase kettingreaksie (PKR) vir die mees bruikbare rekombinant. Tien translokasie rekombinante is geïdentifiseer nadat 159 hemisigotiese toetskruis F1-plante met drie mikrosatelliet-merkers, spesifiek vir chromosoom-arm 2DL, ge-evalueer is. Die rekombinante is hierna met vyf verdere mikrosatellietmerkers getoets. Die data van die agt mikrosatelliet-loci het die rekombinante in twee grootte-kategorieë geplaas waarvan rekombinant #74 die kortste was met slegs die proksimale gedeelte van 2DL wat uit vreemde chromatien bestaan. Behalwe mikrosatellite-merkers is toevallig-geamplifiseerde polimorfiese DNS (RAPD), weerstandsgeen-analoog (RGA), geamplifiseerde volgordelengte polimorfisme (AFLP) en volgorde-gekarakteriseerde geamplifiseerde-streke (SCAR) merkers ook geneties op die translokasie gekarteer. Data van die addisionele merkers het dit moontlik gemaak om die rekombinante in drie grootte-kategorieë te skei. Pogings om ‘n merker vir die kortse rekombinant (#74) te vind, het gelei tot die omskakeling van ‘n 410 bp polimorfiese AFLP-fragment (geproduseer met die ensiem/selektiewenukleotied kombinasie EcoRI - AAC/MseI - CAT), na ‘n dominante, volgordespesifieke PKR-merker. Hierbenewens kan drie mikrosatelliet-merkers wat op rekombinant #74 karteer as resessiewe merkers vir die identifisering van Lr54/Yr37 gebruik word. Die evaluering van die 10 rekombinante met vier chromosoom 2DSspesifieke mikrosatelliet-merkers het ‘n groot delesie van chromosoom-arm 2DS in rekombinant #74 uitgewys. Die delesie mag plant fenotipiese kenmerke beïnvloed en daarom is ‘n strategie vir die vervanging daarvan in rekombinant #74 voorgestel. Ten einde te toets of ‘n geen vir fotoperiode-onsensitiwiteit op die translokaie voorkom is translokasie-draers en kontroles aan lang- en kortdag-behandelings onderwerp en is die effek hiervan op dae-tot-blom gemeet. Geen bewyse vir so ‘n geen kon gevind word nie. ‘n Hoogte-eksperiment om te toets vir die teenwoordigheid van ‘n Rht-geen op die translokasie, het bevestig dat so ‘n geen wel voorkom. Die geen (voorgestelde simbool H) is gekarteer op 2DL en verskil oënskynlik van Rht8 op chromosoom 2DS. Die verskillende chromosoom-ligging van H en Rht8 skakel egter nie die moontlikheid dat hulle ortoloë loci mag wees uit nie. Plant-hoogte data vir rekombinant #74 het daarop gedui dat H nie meer in hierdie rekombinant voorkom nie. Data van ‘n glashuis-eksperiment het daarop gedui dat die vollengte-translokasie 100-korrel-massa verhoog maar dat dit plant-opbrengs verlaag. Aangesien ‘n aansienlike korter rekombinant (#74) verkry is, sal dit ook vir gekoppelde effekte getoets moet word. So ‘n evaluering moet egter onder kommersiële toestande gedoen word met gebruik van naby isogeniese-lyne met en sonder rekombinante chromosoom #74. Die streep-roes weerstandgeen (Yr37) is gekarteer deur hemisigotiese TF2- nageslag van die 10 rekombinante te toets vir weerstand teen Puccinia striiformis patotipe 6E22A+. Rekombinant #74 het beide Lr54 en Yr37 behou en die twee gene karteer dus naby die sentromeer.

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.

Typescript (photocopy). / Digitized by Kansas Correctional Industries

Typescript (photocopy). / Digitized by Kansas Correctional Industries

LD2668 .T4 1954 T64 / Master of Science

Call number: LD2668 .T4 1960 P65