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Thesis (PhD (Agric)) -- Stellenbosch University, 2001. / ENGLISH ABSTRACT: Chromosome arm 7DL of common wheat carries genes for agronomically important traits such as leaf rust, stem rust, Russian wheat aphid and eye spot resistance. Some of these genes occur on introgressed foreign chromatin, which restricts their utility in breeding. The 7DL genetic maps are poorly resolved, which seriously hampers attempts to manipulate the genes and introgressed regions in breeding. This dissertation represents an attempt to improve our knowledge of the relative map positions of three resistance genes that have significant potential for use in local breeding programmes. The leaf rust resistance gene, Lr19, is located on a Thinopyrum ponticum-derived translocation which occupies a large part of the terminal end of 7DL. The translocation also carries genes for less favourable traits such as yellow flour colour. Attempts have been made to reduce the size of the translocation through allosyndetic pairing induction; the primary aims being to remove deleterious genes and to minimise the amount of foreign chromatin associated with Lr19 so it can be recombined with other useful 7DL genes. Twenty-nine 'Indis'-derived Lr 19 deletion mutants were previously produced by gamma irradiation and a physical map was constructed. In this study, the set of mutant lines were further analysed using 144 Sse8387I/Msei and 32 EcoRI/Msel amplified fragment length polymorphism (AFLP) primer combinations. The previous physical map, which was based on five restriction fragment length polymorphism (RFLP) markers and five structural gene loci, was extended and now includes 95 novel AFLP markers (86 Sse8387I/Msei and 9EcoRI!Msel markers), of which seven map close to Lr 19. Most of the deletions could be ordered according to size and the improved map has already been used to characterise shortened recombinant forms of the Lr 19 translocation. An unsuccessful attempt was made to convert one of the seven markers closest to Lr 19 into a sequence-specific marker. However, an AFLP marker located distally from Lr 19 was successfully converted into a sequence-specific marker in collaboration with other researchers. An attempt was also made to map and tag the Russian wheat aphid (RWA) resistance gene, Dn5. A doubled haploid mapping population consisting of 94 lines was created and typed for Dn5, four microsatellite loci and the endopeptidase locus, Ep-Dl. The Dn5 locus mapped 25.4 cM and 28.6 cM distally from Xg.vm111 and Xg.vm437, respectively, but was not linked to Xgwm428, Xgwm3 7 or Ep-Dl. Tagging of Dn5 was attempted by screening twelve homozygous resistant and seven homozygous susceptible F2 lines from a cross between 'Chinese Spring' and 'PI 294994' with 70 Sse8387IIi\1sei AFLP primer combinations. Only two potentially useful polymorphisms (one in coupling and one in repulsion phase) were identified. Conversion of the coupling phase marker to a sequence-specific marker was not successful. The eyespot resistance gene, Pchl , was derived from Triticum ventricosum and is present in the wheat VPM-1. Close association between Pchl and the endopeptidase Ep-Dlb allele has been reported previously. Pchl/Ep-Dl was tagged by screening ten wheat genotypes (each homozygous for the confirmed presence or absence of Pchl and/or Ep-Dl b) with 36 Sse83 87I/ Msei AFLP primer combinations. Three AFLP markers were closely associated with Pchl I Ep-D 1, one of which was targeted for conversion into a sequence-specific marker. The sequence-specific marker contained a microsatellite core motif and was found to be useful for tagging Pchl!Ep-Dl. A genetic distance of 2 cM was calculated between the novel microsatellite marker and Ep-Dl. The microsatellite marker was also polymorphic for the Lr 19 translocation and it was possible to map it between the Wsp-Dl and Sr25 loci. In this dissertation, mapping and/or tagging of three important resistance genes were achieved. Due to the fact that all markers used in these studies were not polymorphic between all of the targeted regions, it was not possible to fully integrate the data obtained for the three regions. / AFRIKAANSE OPSOMMING: Chromosoom arm 7DL van broodkoring dra gene vir agronomies-belangrike kenrnerke soos blaarroes, stamroes, Russiese koringluis en oogvlek weerstand. Sommige van hierdie gene kom voor in blokke spesie-verhaalde chromatien wat hul bruikbaarheid in teling beperk. Die genetiese kaarte van 7DL is swak ontwikkel en dit maak dit baie moeilik om hierdie gene en spesie-verhaalde streke tydens teling te manipuleer. Hierdie proefskrif verteenwoordig 'n paging om kennis van die relatiewe kaart liggings van drie weerstandsgene, met betekenisvolle potensiaal in plaaslike tee! programme, te verbreed. Die blaarroes weerstandsgeen, Lr 19, kom voor op 'n Thinopyrum ponticum-verhaalde translokasie wat 'n groot terminale gedeelte van 7DL beslaan. Die translokasie dra ook gene vir minder gewensde kenrnerke soos gee! meelkleur. Pogings is aangewend om die translokasie deur homoeoloe parings-induksie te verkort. Die doe! was om nadelige gene te verplaas en die hoeveelheid vreemde chromatien geassosieer met Lr 19 te minimiseer sodat dit met ander nuttige gene op 7DL gerekombineer kan word. Nege-en-twintig 'Indis'-verhaalde Lr 19 delesie mutante is vroeer met gamma bestraling geproduseer en gebruik om 'n fisiese kaart op te stel. Teenswoordig is die stel mutante verder ontleed met behulp van 144 Sse8387I!Msei en 32 EcoRII Msel amplifikasie-fragment-lengte-polimorfisme (AFLP) inleier kombinasies. Die bestaande fisiese kaart, wat gebaseer was op vyf restriksie-fragment-lengte-polimorfisme (RFLP) merkers en vyf strukturele geen loki, is uitgebrei en sluit nou 95 unieke AFLP merkers (86 Sse8387I/Msel en 9EcoRI/Msel merkers) in, waarvan sewe naby aan Lr19 karteer. Die meeste van die delesies kon op grond van hulle grootte gegroepeer word en die verbeterde fisiese kaart is alreeds gebruik om verkorte rekombinante vorms van die Lr 19 translokasie te karakteriseer. 'n Onsuksesvolle paging is aangewend om een van die sewe merkers naaste aan Lr 19 om te skakel na 'n volgorde-spesifieke merker. 'n AFLP merker wat distaal van Lr 19 karteer is egter wel suksesvol in samewerking met ander navorsers omgeskakel na 'n volgordespesifieke merker. 'n Paging is ook aangewend om die Russiese koringluis (RKL) weerstandsgeen, Dn5, te karteer en merkers gekoppel aan die geen te identifiseer. 'n Verdubbelde-haplo!ede karteringspopulasie van 94 lyne is geskep en getipeer vir Dn5, vier mikrosatelliet loki en die endopeptidase lokus, Ep-D1. Die Dn5 lokus karteer 25.4 cM en 28.6 cM distaal van Xgwml11 en Xgwm437, respektiewelik, maar was me gekoppel met Xgwm428, Xgwm37 of Ep-D1 me. Twaalf homosigoties weerstandbiedende en sewe homosigoties vatbare F2 lyne uit die kruising: 'Chinese Spring' I 'PI 294994' is met 70 Sse8387VMsel AFLP inleier kombinasies getoets in 'n poging om merkers vir Dn5 te identifiseer. Slegs twee moontlik bruikbare polimorfismes (een in koppelings- en een in repulsie fase ), is ge'identifiseer. Omskakeling van die koppelingsfase merker na 'n volgorde-spesifieke merker was onsuksesvol. Die oogvlek weerstandsgeen, Pch1, is uit Triticum ventricosum oorgedra en kom voor in die koringlyn, VPM-1. Noue koppeling van Pch1 en die endopeptidase alleel, Ep-D1 b, is vantevore gerapporteer. Merkers is vir P chl I Ep-D 1 gevind deur tien koring genoti pes ( elkeen homosigoties vir die bevestigde teenwoordigheid of afwesigheid van Pch1 en/of Ep-D1 b) te toets met 36 Sse83871/kfsel AFLP inleier kombinasies. Drie AFLP merkers is gevind wat nou koppel met Pchl!Ep-D1 , waarvan een gekies is vir omskakeling na 'n volgorde-spesifieke merker. Die volgorde-spesifieke merker het 'n mikrosatelliet kernmotief bevat en was nuttig as merker vir Pch1/Ep-D1. 'n Genetiese afstand van 2 cM is tussen die unieke mikrosatelliet merker en Ep-D1 bereken. Die mikrosatelliet merker was ook polimorfies vir die Lr 19 translokasie en dit is tussen die Wsp-D1 en Sr25 loki gekarteer. Kartering en/of identifikasie van merkers vir drie belangrike weerstandsgene was suksesvol in hierdie studie. Omdat al die merkers wat gebruik is, nie polimorf was tussen al die streke van belang nie, was dit nie moontlik om die data vir elk van die drie streke ten volle te integreer nie.

Typescript (photocopy). / Digitized by Kansas Correctional Industries

Call number: LD2668 .T4 1957 R68 / Master of Science

Doctor of Philosophy / The responses of 92 barley genotypes to selected P. hordei pathotypes was assessed in greenhouse tests at seedling growth stages and in the field at adult plant growth stages to determine known or unknown resistances. On the basis of multipathotype tests, 35 genotypes were postulated to carry Rph2, Rph4, Rph5, Rph12, RphCantala alone or combinations of Rph2 + Rph4 and Rph1 + Rph2, whereas 52 genotypes lacked detectable seedling resistance to P. hordei. Five genotypes carried seedling resistance that was effective to all pathotypes tested, of which four were believed to carry uncharacterised resistance based on pedigree information. Field tests at adult plant growth stages indicated that while 28 genotypes were susceptible, 57 carried uncharacterised APR to P. hordei. Pedigree analysis indicated that APR in the test genotypes could have been derived from three different sources. The resistant responses of seven cultivars at adult plant growth stages were believed to be due to the presence of seedling resistance effective against the field pathotypes. Genetic studies conducted on 10 barley genotypes suggested that ‘Vada’, ‘Nagrad’, ‘Gilbert’, ‘Ulandra (NT)’ and ‘WI3407’ each carry one gene providing adult plant resistance to P. hordei. Genotypes ‘Patty’, ‘Pompadour’ ‘Athos’, ‘Dash’ and ‘RAH1995’ showed digenic inheritance of APR at one field site and monogenic inheritance at a second. One of the genes identified in each of these cultivars provided high levels of APR and was effective at both field sites. The second APR gene was effective only at one field site, and it conferred low levels of APR. Tests of allelism between resistant genotypes confirmed a common APR gene in all genotypes with the exception of ‘WI3407’, which based on pedigree information was genetically distinct from the gene common in ‘Vada’, ‘Nagrad’, ‘Patty’, ‘RAH1995’ and ‘Pompadour’. An incompletely dominant gene, Rph14, identified previously in an accession of Hordeum vulgare confers resistance to all known pathotypes of P. hordei in Australia. The inheritance of Rph14 was confirmed using 146 and 106 F3 lines derived from the crosses ‘Baudin’/ ‘PI 584760’ (Rph14) and ‘Ricardo’/‘PI 584760’ (Rph14), respectively. Bulk segregant analysis on DNA from the parental genotypes and resistant and susceptible DNA bulks from F3 lines using diversity array technology (DArT) markers located Rph14 to the short arm of chromosome 2H. Polymerase chain reaction (PCR) based marker analysis identified a single simple sequence repeat (SSR) marker, Bmag692, linked closely to Rph14 at a map distance of 2.1 and 3.8 cM in the populations ‘Baudin’/ ‘PI 584760’and ‘Ricardo’/‘PI 584760’, respectively. Seedlings of 62 Australian and two exotic barley cultivars were assessed for resistance to a variant of Puccinia striiformis, referred to as BGYR, which causes stripe rust on several wild Hordeum species and some genotypes of cultivated barley. With the exception of six Australian barley cultivars and an exotic cultivar, all displayed resistance to the pathogen. Genetic analyses of six Australian barley cultivars and the Algerian barley ‘Sahara 3771’, suggested that they carried either one or two major seedling resistance genes to the pathogen. A single recessive seedling resistance gene, Bgyr1, identified in ‘Sahara 3771’ was located on the long arm of chromosome 7H and flanked by restriction fragment length polymorphism (RFLP) markers wg420 and cdo347 at genetic distances of 12.8 and 21.9 cM, respectively. Mapping resistance to BGYR at adult plant growth stages using a doubled haploid population derived from the cross ‘Clipper’/‘Sahara 3771’ identified two major QTLs on the long arms of chromosomes 3H and 7H that explained 26 and 18% of total phenotypic variation, respectively. The QTL located on chromosome 7HL corresponded to the seedling resistance gene Bgyr1. The second QTL was concluded to correspond to a single adult plant resistance gene designated Bgyr2, originating from cultivar ‘Clipper’.

Typewritten copy Comparative study of genes for resistance to bunt (Tilletia caries (D.C.) Tul. and T. foetida (Wallr.) Liro); Cytological investigations in Phalaris called part 2.

Copy of author's previously published article inserted. / Bibliography: leaves 60-75. / viii, 75, [40] leaves, [24] leaves of plates : ill. (some 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, Dept. of Crop Protection, 1995?

Includes bibliographical references. / xiv, 210 leaves : ill. ; 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, Dept. of Plant Science, 1995

Copy of author's previously published article inserted. Bibliography: leaves 60-75.