Genomic regions associated with common root rot resistance in the barley variety Delta

Common root rot (CRR) caused by Bipolaris sorokiniana is a serious disease constraint in the dry temperate cereal growing regions of the world. Currently little is known about the genetic control of resistance to CRR in cereals. In this study based on a Delta/Lindwall barley population we have undertaken a bulked segregant analysis (BSA) and whole genome mapping approach utilising Diversity Arrays Technology (DArT) to identified quantitative trait loci (QTL) associated with CRR expression. One QTL each was identified on chromosomes 4HL and 5HL explaining 12 and 11% of the phenotypic variance, respectively

Efficient adaptive sampling applied to multivariate, multiple output rational interpolation models, with applications in electromagnetics-based device modelling

Thesis (PhD) -- Stellenbosch University, 2001.ENGLISH ABSTRACT: A robust and efficient adaptive sampling algorithm for multivariate, multiple output rational interpolation models, based on convergents of Thiele-type branched continued fractions, is presented. A variation of the standard branched continued fraction method is proposed that uses approximation to establish a non-rectangular grid of support points. Starting with a low order interpolant, the technique systematically increases the order by optimally choosing new support points in the areas of highest error, until the desired accuracy is achieved. In this way, accurate surrogate models are established by a small number of support points, without assuming any a priori knowledge of the microwave structure under study. The technique is illustrated and evaluated on several passive microwave structures, however it is general enough to be applied to many modelling problems.AFRIKAANSE OPSOMMING: 'n Robuuste en effektiewe aanpasbare monsternemingsalgoritme vir multi-veranderlike, multi-uittree rasionale interpolasiemodelle, gegrond op konvergente van Thiele vertakte volgehoue breukuitbreidings, word beskryf. 'n Variasie op die konvensionele breukuitbreidingsmetode word voorgestel, wat 'n nie-reghoekige rooster van ondersteuningspunte gebruik in die funksiebenadering. Met 'n lae orde interpolant as beginpunt, verhoog die algoritme stelselmatig die orde van die interpolant deur optimaal verbeterde ondersteuningspunte te kies waar die grootste fout voorkom, totdat die gewensde akuraatheid bereik word. Hierdeur word akkurate surrogaat modelle opgebou ten spyte van min inisiele ondersteuningspunte, asook sonder voorkennis van die mikrogolfstruktuur ter sprake. Die algoritme word gedemonstreer en geevalueer op verskeie passiewe mikrogolfstrukture, maar is veelsydig genoeg om toepassing te vind in meer algemene modelleringsprobleme

Restoration integrity, but not material or cementation strategy determined secondary caries next to indirect restorations in vitro

Einleitung: Sekundärkaries gilt nach wie vor als die Hauptursache für einen Restaurationsaustausch. Zur Sekundärkariesentstehung an indirekten Restaurationen gibt es nur wenige Daten. In der vorliegenden Dissertation wurden der Einfluss approximaler Passungenauigkeiten, verschiedener Befestigungsstrategien und indirekter Restaurationsmaterialien auf die Entstehung von Sekundärkaries an indirekten Restaurationen untersucht. Methodik: Kariesfreie dritte Molaren (n=96) wurden nach standardisierten Verfahren für indirekte Restaurationen präpariert und auf 2 Versuchsgruppen verteilt: Insgesamt 48 Restaurationen, davon 12 aus einer Goldlegierung und 36 aus Lithiumdisilikatkeramik, wiesen einen Randspalt (Mittelwert/Standardabweichung 237/71 µm) im gingivo-zervikalen Bereich auf. Weitere 48 Restaurationen in identischer Aufteilung wurden ohne Spalt hergestellt. Die Goldrestaurationen beider Gruppen wurden mit einem Glasionomerzement (Ketac Cem) befestigt; die Lithiumdisilikatkeramiken wurden ad-häsiv mit Variolink Esthetic DC in Kombination mit dem Adhäsivsystem Syntac, Variolink Esthetic DC in Kombination mit Adhese Universal oder mit dem selbstadhäsiven Befestigungskomposit RelyX Unicem 2 eingegliedert (n=24/Gruppe). Über einen Zeitraum von 10 Tagen wurde im Mastikationsmodell ein kariogener Lactobacillus rhamnosus-Biofilm an den approximalen Zahn-Restaurationsflächen kultiviert. Durch mikroradiografische Untersuchungen wurde der Mineralverlust (∆Z) im Schmelz (Enamel Surface Lesion, ESL) und im Dentin (Dentin Wall Lesion, DWL) ermittelt. Ergebnisse: Randspalt, Befestigungsstrategie und Restaurationsmaterial hatten keinen signifikanten Einfluss auf ∆Z von ESL (p>0.05/Generalized Linear Modelling). ∆Z von DWL war signifikant erhöht bei vorhandenem Randspalt (p=0.003). Befestigungsstrategie und Restaurationsmaterial hatten keinen signifikanten Einfluss (p>0.05). Schlussfolgerung: Unter Berücksichtigung der Limitationen dieser Studie hatte die Qualität einer indirekten Restauration einen größeren Einfluss auf die Sekundärkaries-entstehung als die Befestigungsstrategie oder das Restaurationsmaterial.Introduction: The clinical diagnosis of secondary caries is the most common reason for the replacement of restorations. Only limited data are available on the development of secondary caries adjacent to indirect restorations. This study evaluated the impact of proximal cervical restoration fit (presence of gaps), cementation strategy and restoration material on the development of secondary caries adjacent to indirect restorations. Methods: Caries-free molars (n=96) were prepared following a standardized procedure for indirect restorations and divided into 2 groups: 48 gold (n=12) and lithium disilicate glass ceramic (n=36) restorations showed a cervico-proximal gap (mean value/standard deviation 237/71 µm); another 48 restorations were manufactured without a gap. Gold restorations of both trial groups were cemented with Ketac Cem; lithium disilicate glass ceramic restorations were incorporated adhesively using Variolink Esthetic DC in combination with the adhesive system Syntac, Variolink Esthetic DC in combination with Adhese Universal, or with RelyX Unicem 2, a self-adhesive resin cement (n=24/group). Concomitant to cyclic loading, a cariogenic Lactobacillus rhamnosus biofilm was established over a period of 10 days. The mineral loss (∆Z) in enamel (Enamel Surface Lesion, ESL) and dentin (Dentin Wall Lesion, DWL) was determined by transverse microradiographic analysis. Results: For ESL the presence of an interfacial gap, cementation strategy and restoration material had no significant influence on ∆Z (p>0.05/Generalized Linear Modelling). For DWL, ∆Z was significantly higher adjacent to restorations with interfacial gaps (p=0.003). Cementation strategy and restoration material did not have a significant impact (p>0.05). Significance: Within the limitations of this study, the fit of an indirect restoration had a greater impact on the development of secondary caries than cementation strategy or restoration material

Mapping spot blotch resistance genes in four barley populations

Bipolaris sorokiniana (teleomorph: Cochliobolus sativus) is the fungal pathogen responsible for spot blotch in barley (Hordeum vulgare L.) and occurs worldwide in warmer, humid growing conditions. Current Australian barley varieties are largely susceptible to this disease and attempts are being made to introduce sources of resistance from North America. In this study we have compared chromosomal locations of spot blotch resistance reactions in four North American two-rowed barley lines; the North Dakota lines ND11231-12 and ND11231-11 and the Canadian lines TR251 and WPG8412-9-2-1. Diversity Arrays Technology (DArT)-based PCR, expressed sequence tag (EST) and SSR markers have been mapped across four populations derived from crosses between susceptible parental lines and these four resistant parents to determine the location of resistance loci. Quantitative trait loci (QTL) conferring resistance to spot blotch in adult plants (APR) were detected on chromosomes 3HS and 7HS. In contrast, seedling resistance (SLR) was controlled solely by a locus on chromosome 7HS. The phenotypic variance explained by the APR QTL on 3HS was between 16 and 25% and the phenotypic variance explained by the 7HS APR QTL was between 8 and 42% across the four populations. The SLR QTL on 7HS explained between 52 to 64% of the phenotypic variance. An examination of the pedigrees of these resistance sources supports the common identity of resistance in these lines and indicates that only a limited number of major resistance loci are available in current two-rowed germplasm

Generating sequential space-filling designs using genetic algorithms and Monte Carlo methods

In this paper, the authors compare a Monte Carlo method and an optimization-based approach using genetic algorithms for sequentially generating space-filling experimental designs. It is shown that Monte Carlo methods perform better than genetic algorithms for this specific problem

Genetic analysis of wheat rust resistance genes segregating in a Kariega x Avocet S population

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