The larger grain borer (LGB) Prostephanus truncatus (Horn) is the most important pest of farm stored maize and cassava in Africa. This alien invasive species was introduced into the continent from Mesoamerica in the late 1970s and by 2008 had spread to at least 18 countries. In contrast to indigenous primary storage pests, LGB exists as on-farm and as wild populations, hence, sustainable control must target both environments. Biological control is especially attractive for wild populations to reduce early season grain store infestation, while cultural and chemical methods are useful to protect stored produce directly. Two populations of the predator Teretrius nigrescens Lewis were introduced into several African countries' as a biocontrol agent. It has shown long-term success and cost effective control in warm-humid areas. Control has however not been successful in cool and hot-dry zones. The aim of this study was to investigate the possible underlying genetic and ecological explanations for these observations and the possibility of joint use of molecular markers and ecological parameters in the development of sustainable control strategies. A 28-month baseline monitoring and recovery activity was done in from 2004 in five regions in Kenya along an east-westerly transect. Monitoring and live sample collection was also done in the original outbreak area in eastern Kenya. There was greater LGB flight activity in western Kenya (high potential maize production area) than the low potential areas. Very few T. nigrescens were recovered, solely in the eastern regions. LGB flight activity followed a seasonal pattern mostly related to changes in the relative humidity at 12:00, rainfall and dew point temperature but with a 3 - 4 week lag. A linear predictive model based on these factors predicted 27 % of the observed flight activity. The survival and predation of five strains of T. nigrescens were compared at eight temperature levels between 15 °C and 36 °C at low and high humidity. All the strains of T. nigrescens exerted a significant reduction of LGB population build-up between 21 °C and 33 °C with generally better performance under humid conditions. There was no evidence of T. nigrescens development at 15 °C. At 18 °C, T. nigrescens oviposition and development was observed but the effect on LGB did not differ significantly from the control. The KARI population was the least effective in preventing grain damage at lower temperatures, but performed better than other strains above 30 °C at low humidity conditions. There was no control at 18 °C and 36 °C under both high and low humidity conditions. Since the extent of genetic differentiation in T. nigrescens was unclear from prior studies, several molecular marker techniques were progressively used. The RAPD-PCR did not reveal any genetic diversity between geographical populations. A 1000bp region of the mitochondrial mtCOI gene revealed two distinct clades differing consistently at 26 segregating sites. The two clades can be identified by simple PCR-RFLP procedure using single or double sequential restriction with EcoR1, HincII, RsaI and DdeI digestion. However, the two lineages co-exist among the mid-altitude Central American populations. The internal transcribed spacer regions ITS1 and ITS2 with some neighbouring coding sequences of the ribosomal DNA were cloned and sequenced. The spacer regions were so variable in length and sequence between T. nigrescens and related Histeridae species that direct sequence alignment was not meaningful. Within T. nigrescens, there was intragenomic variability of the spacer regions mostly involving insertions and deletions of variable tandem repeat units predominantly within the ITS regions. The short flanking coding (18S, 5.8S and 21S) regions were conserved across populations and six other Histeridae species. There was no significant secondary structure variation of the ITS regions among populations of T. nigrescens. Twenty-four novel variable microsatellite markers were developed and tested on the Honduras populations. Alleles per locus ranged between two and twelve with observed heterozygosity between 0.048 and 0.646. Six loci deviated significantly from Hardy Weinberg Equilibrium and possibly had null alleles. The success of microsatellite amplification in outgroup species and variability of markers declined with an increase in the phylogenetic distance between the test species and T. nigrescens. Genotyping 432 individuals from 13 geographic populations revealed a comparatively higher genetic diversity in field populations. Partial isolation by distance and time was observed. Population bottlenecks were not detected, but recent expansion was evident in laboratory populations. Although five dominant genetic clusters were identified by Bayesian methods, meaningful hierarchical population structure was observed at between two and nine population groups (p < 0.01; 10,000 iterations). Biological control of the larger grain borer using T. nigrescens seems an important aspect of the sustainable integrated control approach of the pest. Ecological adaptations, appropriate release strategies and genetic diversity are all essential considerations in these efforts and could be responsible for the variable success already observed. There is some genetic differentiation between populations of T. nigrescens but, further studies would be necessary to ascertain the contribution of such diversity to its predatory performance. The effect of laboratory culturing in aggravating genetic drift should be accommodated to avoid loss of diversity during sampling, quarantine, rearing and release of the predator. / Thesis (Ph.D. (Environmental Science))--North-West University, Potchefstroom Campus, 2009.

Hieracium lepidulum is an invasive weed in New Zealand. It colonises a wide range of habitats including pine plantations, scrubland, native Nothofagus forest, and mid-altitude to alpine tussock grassland, where it is competing with indigenous species. Understanding the breeding systems and population genetic structure of H. lepidulum is important for biocontrol, and aids in the understanding of evolutionary colonisation processes. H. lepidulum is a triploid, diplosporous, obligate apomict. This type of reproduction through clonal seed does not involve meiosis or fertilisation, and theoretically populations should contain very low levels of genetic variation, the only source being somatic mutation. Common garden experiments and microsatellite markers were used to determine the population genetic structure of H. lepidulum populations in the Craigieburn Range, Canterbury. Both experiments revealed that populations, sampled from three replicate altitudes within three geographically-separated locations, contained no genetic variation; individuals all possessed the same microsatellite genotype. These results strongly suggest that the Craigieburn Range H. lepidulum individuals reproduce solely by apomixis and populations belong to the same clonal lineage. Populations were also examined for their response to two abiotic environmental ‘stresses’, drought and shade. H. lepidulum populations’ exhibited high drought tolerance, yet appeared to be shade-intolerant. Low levels of reproduction in light-limiting habitats will prevent the invasion of H. lepidulum into closed-canopy forest habitats. H. lepidulum appears to have overcome the reduction in fitness associated with apomictic reproduction by phenotypic plasticity, fixed heterozygosity and polyploidy – all associated with increased vigour, fitness, and the ability to occupy broader ecological niches. This study’s results are hopeful for the development of biocontrol programs involving genotype-specific pathogens but suggest that grazing management may not succeed. The data will be useful for future comparisons of genetic structure during the course of H. lepidulum invasions and will contribute to the management of this invasive weed.

Diss. (sammanfattning) Uppsala : Sveriges lantbruksuniv., 2004. / Härtill 4 uppsatser.

Diss. (sammanfattning) Uppsala : Sveriges lantbruksuniversitet, 2004. / Härtill 4 uppsatser.

Thesis (M.S.)--Oregon State University, 2009. / Printout. Includes bibliographical references. Also available on the World Wide Web.

Thesis (Ph. D.)--University of Canterbury, 2008. / Typescript (photocopy). Includes bibliographical references. Also available via the World Wide Web.

Thesis (Ph.D.)--University of Wollongong, 2004. / Typescript. Includes bibliographical references: p. 241-260.

Thesis (MSc (Genetics))--University of Stellenbosch, 2007. / The aim of this study was to develop a DNA-based diagnostic system that can be used to distinguish between genotypes in the wheat breeding program at the University of Stellenbosch. Known marker systems were investigated and the chosen marker system would then be implemented to determine its utility in the breeding program. Three marker systems were considered, i.e. microsatellites, Amplified Fragment Length Polymorphisms (AFLPs) and various retrotransposon-based markers. Each system is based on polymerase chain reaction (PCR) amplification from specific primer pairs. The multitude of primer options was narrowed down during a review of published literature regarding wheat molecular markers. Thirty nine microsatellite primer pairs and nine AFLP primer combinations were chosen for the initial genotype evaluation. Four different retrotransposonbased techniques were investigated; namely Inter-Retrotransposon Amplified Polymorphism (IRAP), REtrotransposon-Microsatellite Amplified Polymorphism (REMAP), Sequence- Specific Amplified Polymorphism (SSAP) and, a derivative of these developed in this study, Wis-2 Retrotransposon Amplification. The study started with twenty genotypes which included varieties/breeding lines from five breeding programmes. The genotypes were chosen as representative of the respective breeding populations and were used in the initial testing of the marker systems. Eighteen microsatellites were evaluated using the panel of twenty genotypes. From this, six primer pairs (Xgwm190, Xgwm437, Xgwm539, Xwmc11, Xwmc59 and Xwmc177) were chosen to test the semi-automated DNA sequencer detection system. A single band/peak in each microsatellite profile was used for genotyping. Four of the primer pairs were labelled with different fluorochromes which enabled them to be multiplexed. The differences in amplification products of the six microsatellites meant that all six could be detected in one electrophoresis run. The banding pattern produced by microsatellite Xwmc177 was complex and highly polymorphic and was therefore also analysed in the same way as the AFLP patterns. When analyzed in this manner it proved to be more informative than the combination of six microsatellites (with a single prominent band scored in each). Three AFLP primer combinations could also be multiplexed and visualised together. The three EcoRI selective primers were labelled with different dyes and used with one MseI selective primer. The SSAP system also used fluorescently labelled primers and proved to be the most useful of the retrotransposon-based methods. However, this system produced such a large amount of data that it made analysis too time consuming. Therefore the six microsatellites and three AFLP primer combinations (MseI-CTC and EcoRI-ACA, -AAC, - AGG) were selected for routine genotyping. Due to the numerous highly polymorphic bands produced by the SSAP system it could be very useful to differentiate very closely related genotypes that cannot be distinguished with the markers proposed for routine use. A panel of 119 breeding lines were then used to implement the two chosen marker systems. The results obtained for these markers were used to produce a dendrogram of the lines using the SAS cluster analysis function. The clusters showed that most of the lines could be distinguished from each other. The MseI-CTC and EcoRI-AGG primer combination was the most informative. It produced the largest number of clusters (53) and could therefore discriminate between more of the lines than any other method. The dendrograms and clusters allowed sixteen of the breeding lines to be selected to test the optimal number of seeds to represent an entire population (variety/breeding line) as one seed was not sufficient. It was decided that eight seeds could provide a good representation of the intra-line variability.

Thesis (MSc)--University of Stellenbosch, 2008. / ENGLISH ABSTRACT: The five leading abalone producers in South Africa have initiated a genetic enhancement program for Haliotis midae in a collaborative effort to improve economically valuable traits. Several independent objective-specific studies were initiated, including the establishment of a Performance Recording Scheme (PRS), utilised in this study, and necessary to monitor the ongoing performance of individuals as the move from mass-selection to marker assisted selection (MAS) is implemented. The primary objective of this study was parentage assignment of F1 offspring mass-selected for size at approximately one year and allocated to either a “faster” or a “slower” growth group. Nine microsatellite markers were used to genotype juveniles and potential parents, with assignment completed using CERVUS 2.0. Average growth results for Abagold and HIK were comparable for both growth groups. Slight environmental effects, although not statistically significant, were evident as growth advantages for juveniles within the faster growth group at two of the five locations and for juveniles within the slower growth group at one of the five rearing locations. Despite measures to standardise environmental influences, variables are difficult to control within the reality of a production environment; and potential genotype x environment interactions may require further investigation and factoring into future breeding programs. The additional costs associated with MAS often make the technology prohibitive to most aquaculture operations, despite the significant genetic gains to be realised from its implementation. Cost-optimising routine processes such as DNA extractions may be one approach to reduce these additional costs. Chelex®100 appears to be a suitable alternative to the CTAB method – being quick and cost-effective to perform. Applying this method in combination with the high throughput of a robotic platform warrants further evaluation. For the microsatellite development, 50% of positive recombinant clones contained inserts. Sequencing of these clones produced 16% perfect repeats and 47% imperfect repeats for which 52 primer sets were designed and tested. In total, 31 polymorphic microsatellite loci of different motifs and composition were developed. Sixty-one percent of sequenced clones were deemed redundant and pre-screening for both uniqueness and the presence of microsatellites would reduce unnecessary sequencing thus improving the efficiency of the FIASCO method and reducing costs. Nine loci were selected for parentage assignments. Null alleles were present for all the selected markers; however, frequencies were below the critical level of 5%. Parentage yielded 91% and 90% successful assignment for Abagold and HIK respectively; however, observations indicate that a measure of relatedness may exist between breeders. Recommendations with regards to future family breeding include, for both Abagold and HIK, retaining selected breeders based on their respective contributions to the F1 progeny while reassessing the potential of remaining breeding stock under more controlled breeding conditions. No obvious trends were observed for growth with most individuals producing both faster and slower growing offspring. Juveniles will be reassessed at two years to determine whether the size advantage or disadvantages were maintained and to ascertain whether growth advantages/disadvantages may be gender specific. / AFRIKAANSE OPSOMMING: Die vyf mees toonaangewende perlemoen produseerders in Suid Afrika het „n genetiese verbeteringsprogram vir Haliotis midae geinisieer in „n gesamentlike poging om ekonomiese belangrike eienskappe te verbeter. Verskeie onafhanklike fokus-spesifieke studies is geinisieer, insluitend die totstandkoming van „n groeiprestasie aantekenstelsel, soos gebruik in hierdie studie, en wat noodsaaklik is om die aaneenlopende prestasie van individue te moniteer soos daar beweeg word van massa seleksie tot merker bemiddelde seleksie. Die primêre fokus van hierdie studie was die ouerskapsbepaling van F1 nageslag wat massa geselekteer is op ouderdom 1 jaar vir grootte en as of “vinniger” of “stadiger” groeiers geklassifiseer is. Nege mikrosatelliet merkers is gebruik om jong perlemoen individue en moontlike ouers te genotipeer, met die ouerskapstoekenning bereken deur CERVUS 2.0. Groei resultate vir Abagold en HIK was vergelykbaar vir beide groei groepe op drie van die lokaliteite. Geringe omgewingseffekte, alhoewel nie statisties betekenisvol nie, was sigbaar as „n groei voordeel vir jong individue op twee van die vyf lokaliteite. Ongeag maatstawe om omgewingsinvloede te standardiseer, is varieerbares moeilik om te beheer in die produksie omgewing en genotipe x omgewings interaksies mag verdere navorsing vereis en behoort in ag geneem te word in toekomstige telingsprogramme. Die onkoste wat met merker bemiddelde seleksie geassosieer word, maak die tegniek soms onaantreklik vir die meeste akwakultuur operasies; nie teen staande die genetiese voordele wat die gebruik daarvan veroorsaak. Die koste-optimiseering van roetine prosesse, soos byvoorbeeld, DNA ekstraksies, is dalk een aanslag om die addisionele koste te verminder. Chelex®100 blyk „n geskikte alternatief tot die CTAB metode te wees – die tegniek is vinnig en koste-effektief om uit te voer. Die gebruik van hierdie metode in kombinasie met die hoë deurvloei van ‟n robotiese sisteem behoort verder ondersoek te word. Vir die mikrosatelliet ontwikkeling het slegs 50% van die positiewe rekombinante klone invoegings bevat. Nukleotiedvolgorde bepaling van hierdie klone het 16% perfekte herhalings en 47% onderbroke herhalings bevat waaruit 52 inleierstelle ontwikkel en getoets is. In totaal is 31 polimorfiese mikrosatelliet loki van verskillende motiewe en samestelling ontwikkel. Een-en-sestig persent van die volgorde bepaalde klone is oortollig geag en vooraf sifting vir beide uniekheid en die teenwoordigheid van mikrosatelliete sal onnodige volgorde bepaling verhoed, die effektiwiteit van die FIASCO tegniek verhoog sowel as addisionele koste verminder. Nege loki is geselekteer vir ouerskapsbepaling. Nul allele was teenwoordig vir al die geselekteerde merkers, maar die frekwensies was egter laer as die 5% kritieke waarde. Ouerskap is 91% en 90% suksesvol bepaal vir Abagold en HIK onderskeidelik. Waarnemings dui egter daarop dat daar verwantskappe mag wees tussen van die broeidiere. Voorstelle in terme van toekomstige familie teling sluit is, vir beide Abagold en HIK, om geselekteerde broei diere te behou gebaseer op hulle onderskeie bydraes tot die F1 nageslag asook die herevaluaring van die potensiaal van die oorblywende broei diere onder meer beheerde teling toestande. Geen voor-die-handliggende tendense is waargeneem vir groei nie met die meeste individue wat beide vinniger en stadiger groeiende nageslag geproduseer het. Jong individue moet geherevalueer word op tweejarige ouderdom om te bepaal of die groei voordeel of nadele behou is en om te bepaal om groei voordele/nadele geslagspesifiek is.

Thesis (MScAgric)--Stellenbosch University, 2002. / ENGLISH ABSTRACT: Grapevine supports one of the oldest industries in South Africa today, and is also of significant international importance. With increasing international trade and the transport of fruit and other grapevine-derived products between borders, it has become increasingly important for South African farmers and viticulturalists to ensure their products conform to strict international market requirements if they are to remain competitive. Such requirements include the correct and accurate identification of berries and wines according to cultivar. In light of this, 26 different wine, table grape and rootstock cultivars, as well as a number of clones from KWV's core germplasm collection were characterised at 16 microsatellite marker loci. Microsatellite markers are known for their high level of informativeness, reliability and reproducibility, and are widely used in the identification and characterisation of plant varieties, population analyses and forensic applications. Unique allelic profiles were obtained for all but two plants, which proved to be identical at all loci considered, and thus 'clones'. These profiles were collated to form a database, containing the DNA fingerprints of each sample at each locus. The relative levels of informativeness of each marker used were also determined, and compared with those found in the literature. Six markers proved to be highly informative, and are promising in the potential application of this technology to other cultivars. The applicability of microsatellite markers to such studies is confirmed; this approach could easily be extended to include any number of cultivars of national and international interest. The results of such an investigation would have important implications for both the farming and commercial industries alike. / AFRIKAANSE OPSOMMING: Wingerd ondersteun een van die oudste industriee in Suid-Afrika vandag, en is ook van groat intemasionale belang. Met die toenemende intemasionale ruilhandel en die vervoer van vrugte en ander wingerd produkte tussen grense, het dit toenemend belangrik geword vir SuidAfrikaanse wingerdboere om te. verseker dat hulle produkte voldoen aan die streng vereistes van die intemasional mark, indien hulle kompeterend wil bly. Hierdie vereistes sluit in die korrekte en akkurate identifisering van druiwe en wyn volgens kultivar. Met hierdie vereistes in ag geneem, is 26 verskillende wyn, tafeldruif en wortelstok kultivars, asook 'n aantal klone van die KWV se kern kiemplasma versameling, gekarakteriseer by 16 mikrosatelliet merker loki. Mikrosatelliet merkers word gekenmerk deur 'n hoe vlak van informatiwiteit, betroubaarheid en herhaalbaarheid en word wydverspreid gebruik in die identifisering en karakterisering van plant varieteite, populasie analises en forensiese toepassings. Unieke alleliese profiele is vir a1 die plante verkry, behalwe vir twee plante wat identiese resultate by alle loki opgelewer het en dus as "klone" beskou kan word. Hierdie profiele is bymekaar gevoeg om 'n databasis te vorm wat die DNA vingerafdrukke van elke monster by elke lokus bevat. Die relatiewe vlak van informatiwiteit van al die merkers is ook bepaal en vergelyk met merkers in die literatuur. Ses van die merkers blyk om hoogs informatief te wees en lyk belowend in die potensiele toepassing van hierdie tegnologie op ander kultivars. Die toepaslikheid van mikrosatelliet merkers op sulke studies is bevestig; hierdie benadering kan maklik aangepas word om enige aantal kultivars van nasionale en intemasionale belang in te sluit. Die resultate van s6 'n ondersoek sal belangrike implikasies inhou vir beide die boerdery en kommersiele industriee.