Detección presintomática y no destructiva de enfermedades causadas por patógenos de suelo en maíz (Marchitez tardía) y en girasol (Jopo) mediante medidas térmicas y de fluorescencia multicolor

Algunas enfermedades de cultivos originadas por patógenos de suelo se caracterizan por la tardía aparición de síntomas. Este es el caso de la Marchitez tardía del maíz (causada por el hongo Harpophora maydis) y del Jopo del girasol (causado por la planta parásita de raíz Orobanche cumana). Harpophora maydis se refirió por vez primera en la Península Ibérica en 2010 y durante los últimos años se ha convertido en una preocupación importante para los productores de maíz. Por el contrario, los ataques de O. cumana son frecuentes en los cultivos españoles de girasol desde los años 80. Esta parásita es actualmente el principal limitante biótico de la producción de aceite de girasol en el mundo. Tanto H. maydis como O. cumana infectan la planta hospedante durante las primeras semanas después de la siembra, aunque los síntomas no se hacen visibles hasta la floración del cultivo o poco después de que ésta tenga lugar. También ambas enfermedades se controlan mediante la incorporación de genes de resistencia en las variedades cultivadas. El progreso y el éxito de los programas de mejora para resistencia a enfermedades dependen enormemente de un acertado y eficaz diagnóstico de la reacción de la planta hospedante al patógeno. Por otro lado, en la actualidad son frecuentes las técnicas basadas en el uso de sensores lejanos y/o de proximidad utilizadas en agronomía. Como alternativa a la inspección visual y al análisis de ADN destructivo, y debido a su sensibilidad a desórdenes fisiológicos en las plantas asociados al ataque de patógenos, estas técnicas pueden ser eficaces herramientas de detección en fitopatología. En el caso de proximidad, la monitorización indirecta de las plantas se efectúa principalmente mediante termometría, termografía,medidas de fluorescencia y técnicas espectrales. En el Capítulo 1 de esta Tesis Doctoral se desarrolla el estado del arte de la Marchitez tardía del maíz y del Jopo del girasol. También se presenta información científica actualizada sobre las técnicas de sensores lejanos y/o de proximidad utilizadas más comúnmente en fitopatología. Los objetivos se presentan en el Capítulo 2. En primer lugar se estudió la distribución de H. maydis en la Península Ibérica, se caracterizó su patogenicidad y también se determinaron otras especies de hongos presentes en maíz afectado por marchitez. Además, se evaluó el potencial de la termometría infrarroja para detectar las infecciones por H. maydis. En segundo lugar se detectó la presencia de O. cumana en girasol durante las fases de crecimiento subterráneo de la planta parásita utilizando para ello imágenes de fluorescencia multicolor (FMC). También se consideraron las posibles alteraciones fisiológicas en el girasol como consecuencia de la infección por O. cumana. En el Capítulo 3 se estudió la distribución geográfica de H. maydis en las principales zonas de cultivo de maíz en España y el sur de Portugal, prospectando 59 campos entre 2009 y 2013. La identidad de 14 de entre todos los aislados de H. maydis obtenidos se confirmó mediante amplificación ITS y estos mismos aislados se caracterizaron por su agresividad mediante inoculación y crecimiento de maíz susceptible crecido en condiciones de umbráculo durante todo el ciclo del cultivo. Uno de los aislados del hongo fue muy agresivo, causando síntomas severos en las plantas y reducciones significativas de peso de sus raíces y partes aéreas. Los aislados moderadamente agresivos causaron valores de enfermedad significativos, pero no todos ellos se asociaron a reducciones de peso de las plantas. En 2012 y 2013 se monitorizó la infección por H. maydis en maceta al aire libre y mediante medidas de temperatura de cubierta y del índice de estrés hídrico del cultivo en plantas control y en plantas inoculadas con el aislado más agresivo. Ambos índices respondieron a la infección por el hongo en los dos años, pudiendo detectarse dicha infección hasta 17 días antes de que los síntomas fueran visibles. Este estudio ha revelado la amplia distribución de H. maydis, que se localiza en los valles de todos los ríos de la Península Ibérica excepto el del Ebro y pone de relieve la importancia de la resistencia genética para controlar este patógeno en el sur de Europa. Además, la detección térmica de la infección previa al desarrollo de síntomas podría resultar en aplicaciones útiles para el diagnóstico presintomático y no destructivo de la enfermedad. En el Capítulo 4 se determinaron las especies de hongos asociadas a H. maydis como agente causal de marchitez de maíz. Para ello, se muestrearon 19 campos con síntomas de marchitez en las principales zonas de cultivo de la Península Ibérica entre 2011 y 2012. En el 47% de ellos no se identificó H. maydis sino otras especies: Fusarium graminearum, F. verticillioides, F. equiseti, F. proliferatum, Macrophomina phaseolina, Rhizoctonia solani y Trichoderma harzianum. En los campos restantes, junto a H. maydis se identificaron otros hongos de suelo en porcentajes apreciables: F. verticillioides (19%), F. proliferatum (19%), F. equiseti (9%), F. oxysporum (9%) y Pythium oligandrum (9%). El crecimiento vascular de H. maydis y de otras especies de hongos en maíz se confirmó analizando plantas con marchitez procedentes de tres campos diferentes. Tanto H. maydis como F. graminearum, F. equiseti, F. proliferatum y T. harzianum se recuperaron de la inserción entre la raíz y tallo y a 10 cm de altura en el tallo de las plantas. El efecto de la infección por H. maydis sobre la producción de las plantas de maíz se cuantificó en macetas y condiciones seminaturales en 2011. El peso de las mazorcas de plantas inoculadas se redujo en un 54%. Estas plantas también tuvieron pesos de raíz y de parte aérea (tallo y hojas) significativamente menores que los de las plantas control. Estos resultados apuntan al gran impacto que puede tener la Marchitez tardía sobre la producción de maíz en campo. Además, y aunque la patogenicidad de los hongos de suelo identificados en maíz debería ser confirmada, los resultados de este trabajo sugieren que la Marchitez tardía del maíz puede tener una etiología compleja. En cuanto al Capítulo 5, en él se analizó por primera vez la fluorescencia emitida por la clorofila de girasol en las bandas espectrales con máximos en el rojo (F680) y en el rojo lejano (F740). Se incubaron plantas sanas de girasol en macetas y condiciones de invernadero y, entre la segunda y la quinta semana de crecimiento se compararon los patrones de emisión de fluorescencia de los cuatro primeros pares de hojas (PHs) tanto en la superficie de la hoja como entre PHs. Los PHs de plantas sanas de girasol presentaron similares patrones de fluorescencia, tanto en el rojo como en el rojo lejano, que variaron dependiendo del grado de desarrollo de la hoja. La utilidad de F680 y F740 como indicadores de la infección de girasol por O. cumana durante las fases de desarrollo subterráneo de la plana parásita se evaluó en condiciones experimentales similares. En plantas infectadas por O. cumana se detectaron aumentos tempranos de F680 y F740, así como reducciones del ratio F680/F7403. Por otro lado, la significación de las diferencias de fluorescencia emitida por plantas control y plantas inoculadas dependió del PH que se considerara en cada momento. Las medidas de contenido clorofílico y de contenido de clorofila total apoyaron los resultados de la FMC, aunque fueron menos sensibles en la discriminación de plantas control y plantas inoculadas. Al final del experimento se confirmó la infección del girasol por la presencia de nódulos en las raíces de las plantas. Este trabajo revela el potencial de la fluorescencia en las regiones del rojo y el rojo-lejano para detectar de forma temprana la infección de girasol por O. cumana, lo que podría ser especialmente interesante para llevar a cabo un fenotipado temprano de material de programas de mejora. Más aún, y hasta donde hemos podido conocer, este es el primer trabajo donde se analiza el efecto de una planta parásita sobre su hospedante utilizando imágenes de fluorescencia en el rojo y en el rojo lejano. En el Capítulo 6 se analizó la emisión de fluorescencia azul y verde (FAV) en hojas de plántulas sanas de girasol. Además, se aplicaron tanto la FAV como la técnica de termografía para detectar la infección del girasol por O. cumana durante el desarrollo subterráneo de la planta parásita. En ambos experimentos se incubaron las plantas de girasol en macetas en invernadero y las medidas se tomaron tras el traslado temporal a cámara de condiciones controladas. En el primer experimento se observó que la FAV emitida por hojas de girasol sano aumentaba a lo largo de su desarrollo. En el caso de girasol parasitado, las hojas presentaban emisiones de FAV menores, y esta diferencia respecto a las hojas de las plantas control fue consistente a lo largo de todo su desarrollo. Al final del experimento se obtuvieron menores concentraciones de pigmentos, lo que sugiere que en las hojas de girasol ocurre un descenso de metabolitos secundarios tras la infección por O. cumana. Por otro lado, a lo largo de todo el experimento se detectaron mayores temperaturas de hoja en girasol inoculado con O. cumana en comparación con la temperatura de hojas de plantas control. Esto podría indicar que el ataque de la planta parásita induce un cierre estomático y una reducción de la transpiración del girasol. En el trabajo de nuevo se ha demostrado que es posible efectuar una monitorización no destructiva de la infección de girasol por O. cumana, en este caso utilizando FAV y termografía, y que dicha monitorización podría aplicarse al fenotipado rápido de girasol. Además, ambas técnicas se han revelado como útiles aproximaciones para estudiar los procesos mediante los cuales O. cumana altera la fisiología de su hospedante (metabolismo secundario y fotosíntesis). Por último, la discusión general de todos los resultados obtenidos en esta Tesis Doctoral y las conclusiones derivadas se presentan en los Capítulos 7 y 8 respectivamente.Some crop diseases caused by soilborne pathogens are characterised by very late symptoms appearance. This is the case of Late wilt of maize (caused by the fungus Harpophora maydis) and that of Broomrape of sunflower (caused by the root parasitic plant Orobanche cumana). Harpophora maydis was first reported in the Iberian Peninsula in 2010, and during the last years it has become a major concern to maize growers. On the contrary, attacks of O. cumana are frequent in sunflower growing areas of Spain since the 1980’s. Currently, the parasite is the first biotic constraint to sunflower oil production worldwide. Both H. maydis and O. cumana infect the host plant during the first weeks after sowing but symptoms are not observed until flowering or shortly after it. Also, they are controlled through the incorporation of genes of resistance into the crop varieties. The advancement and success of breeding programmes is highly dependent on an accurate and fast screening of the reaction of the host plant to the pathogen. On the other hand, techniques based on the use of remote and/or proximal sensors are frequently used with agronomical purposes. As an alternative to visual inspection and to destructive analyses of DNA, and because its sensitivity to physiological disorders in plants associated with pathogen attack, these techniques can constitute efficient detection tools in phytopathology. In the case of near distance, indirect monitoring of plants is majorly conducted by means of thermometry, thermography, fluorescence measurements and spectral techniques. In Chapter 1 of this Ph.D. Thesis, the state of the art of maize late wilt and sunflower broomrape is presented, as well as updated scientific information about the remote and proximal sensing techniques that are most commonly used in plant pathology. The objectives are presented in Chapter 2. First, the distribution of H. maydis in the Iberian Peninsula and its pathogenic characterization were addressed as well as the identification of other fungal species found in symptomatic maize. Also, the utility of infrared thermometry on the detection of maize infections by H. maydis was assessed. Second, the presence of O. cumana in sunflower was analysed during underground development stages by means of multicolour fluorescence (MCF). Possible physiological disorders in sunflower as a consequence of O. cumana infection were also considered. In Chapter 3 the geographical distribution of H. maydis in the main maize growing areas in the South of Portugal and Spain was determined by prospecting 59 fields from 2009 to 2013. Fourteen out of all the isolates of H. maydis were molecularly confirmed by ITS amplification, and their aggressiveness was analysed by inoculation and growth of susceptible maize under shadehouse conditions for the whole growing season. One of the isolates was highly aggressive, causing severe symptoms as well as significant weight reductions of both aboveground parts and roots of the inoculated plants. Moderately aggressive isolates caused significantly high symptoms severity, but not all of them were related to reductions in plant weight. In 2012 and 2013, the infection by H. maydis was monitored outdoors by means of measurements of canopy temperature and crop water stress index of potted control plants and plants inoculated with the most aggressive isolate. Both indices responded to the presence of fungal infection in both years, this infection being detected up to 17 days before symptoms in the plants were visible. This study shows the distribution of H. maydis in all the river valleys of the Iberian Peninsula, except that of the Ebro River, and highlights the importance of genetic resistance for controlling the pathogen in southern Europe. In addition, the thermal detection of the infection prior to symptoms development was possible, what might be further applied to the non-destructive pre-symptomatic diagnosis of Late wilt of maize. The species of fungi that are associated to H. maydis as the causal agent of maize wilt were identified in Chapter 4. Surveys were conducted in 2011 and 2012 in 19 fields where symptomatic plants were collected. The fields were located in the main maize growing areas of the Iberian Peninsula. In 47% of them the fungus infecting diseased plants was not H. maydis but Fusarium graminearum, F. verticillioides, F. equiseti, F. proliferatum, Macrophomina phaseolina, Rhizoctonia solani and/or Trichoderma harzianum. In the remaining fields H. maydis was identified together with other soilborne fungi that were also frequently isolated from diseased plants: F. verticillioides (19%), F. proliferatum (19%), F. equiseti (9%), F. oxysporum (9%) and Pythium oligandrum (9%). The vascular growth of H. maydis and other fungi into the host was confirmed by means of tissue analyses of diseased plants collected at three different locations. Harpophora maydis, as well as F. graminearum, F. equiseti, F. proliferatum and T. harzianum were recovered from the root-stem insertion, and from stem tissues up to 10 cm high. The effect of the infection by H. maydis on maize yield was assessed in inoculated potted plants that were grown in shadehouse in 2011. Cob production was reduced in 54% upon fungal infection. In addition, significantly low weights of roots and aboveground parts (stems and leaves) were obtained. These results point to the great economic impact that Late wilt can have on the yield of maize under field conditions. Likewise, this work suggests that it can be a disease of a complex etiology. Further work should address the pathogenicity of fungal species other than H. maydis on maize, so that the role they may play on disease incidence and on symptoms severity can be determined. Concerning Chapter 5, the fluorescence emitted by chlorophyll (Chl) of sunflower leaves in the spectral bands with peaks near red (F680) and far-red (F740) was analysed for the first time. Healthy sunflowers were grown in pots under greenhouse conditions. Fluorescence emission patterns across the leaf surface and throughout the plant were compared for the first four leaf pairs (LPs) and between the second and fifth weeks of growth. Similar fluorescence patterns, with a delay of three or four days between them, were obtained for LPs of healthy sunflower, showing that red and far-red fluorescence varied with the developmental stage of the leaves. The use of F680 and F740 as indicators of the infection of sunflower by O. cumana during underground development stages of the parasite was also evaluated under similar experimental conditions. Early increases in F680 and F740 as well as decreases in F680/F740 were detected upon infection, significant differences between inoculated and control plants being dependent on the LP that was considered at any time. Measurements of Chl contents and final total Chl content supported the results of MCFI, although they were less sensitive in differentiating healthy from inoculated plants. The infection of sunflowers was confirmed by the presence of broomrape nodules in the roots at the end of the experiment. This work revealed the potential of MCFI in the red and far-red regions for early detecting O. cumana in sunflower, what might be particularly interesting for early phenotyping in sunflower breeding programmes. Furthermore, and to the best of our knowledge, this is the first time that the effect of a parasitic plant in its host is analysed by means of MCFI. In Chapter 6 we analysed the blue-green fluorescence (BGF) emission of leaves of healthy sunflower plantlets, and we implemented BGF and thermal imaging in the detection of the infection by O. cumana during underground parasite development. In both experiments sunflowers were grown in pots and under greenhouse conditions and measurements were made after temporary movement to chamber of controlled conditions. Increases in BGF emission were observed in leaf pairs of healthy sunflowers during their development. Besides, lower BGF emission was consistently detected in parasitised plants throughout leaf expansion, and low pigment concentration was obtained at final time, supporting the interpretation of a decrease in secondary metabolites upon parasite infection. Also, parasite-induced stomatal closure and transpiration reduction were suggested by warmer leaves of inoculated sunflowers throughout the experiment. Techniques of BGF and thermal imaging allowed the non-destructive monitoring of sunflower broomrape, and they could be implemented for fast screening of sunflower genotypes. Additionally, these techniques were shown as valuable approaches to assess the processes by which O. cumana alters physiology (secondary metabolism and photosynthesis) of sunflower. Finally, the general discussion of all the results from the work included in this Ph.D. Thesis and the conclusions drawn from them are presented in Chapters 7 and 8 respectively

Molecular differences between GM- and non-GM crops over-estimated?

Peer reviewed contribution available on the following websites:Public Research Initiative: www.pubresreg.orgEuropean Federation of Biotechnology: http://www.efb-central.org/Nepal Journal of Biotechnology. Jan. 2011, Vol. 1, No. 1 : 31-4

A molecular cytogenetic analysis of introgression in Alstroemeria

This thesis describes the results of a molecular cytogenetic investigation of the process of introgression in Alstroemeria . The aim of this study was to transfer chromosomes or genes from one Alstroemeria species into another. For this, two distantly related species, A. aurea and A. inodora , were hybridized and the resulting hybrids were further backcrossed with the species A. inodora . To monitor the process of introgression accurately it was necessary to identify the individual chromosomes of both parental species.In addition to classical karyotyping, reliable criteria for unequivocal identification of all individual somatic chromosomes of the species A. aurea and A. inodora have been developed by applying fluorescence in situ hybridization (FISH) with tandemly repeated DNA probes (Chapter 2). Four probes, two species specific, A001-I (for A. aurea ) and D32-13 (for A. inodora ), and two ribosomal rDNA repeats, pTa71 (18S-25S) and pTa794 (5S), revealed specific banding patterns per chromosome, enabling identification of all individual chromosomes. In contrast to most plant species, both Alstroemeria species contained a large number of rDNA sites (per haploid genome: 20 in A. aurea and 16 in A. inodora ). Remarkably, the physical location of the rDNA sites varied greatly between the two species; only a few were found at similar positions.Besides identification of somatic chromosomes, FISH with the species specific probes was used for the identification of meiotic chromosomes to accurately determine the extent of homoeologous association in the diploid parental hybrid. Multicolour FISH experiments revealed a large number of bivalents per Metaphase I cell (average 6.7 bivalents per MI) of the hybrid A. aurea x A. inodora , which indicated that homoeologous recombination occurs frequently in the hybrid.Successful backcrossing of the highly sterile distant hybrid A. aurea x A. inodora with its parent A. inodora resulted in a small number of first generation backcross plants (BC1). To establish whether and how frequently homoeologous recombination occurred during meiosis in the hybrid, the BC1 plants were analysed with genomic in situ hybridization (GISH). The presence of recombinant chromosomes in all plants provided evidence for homoeologous recombination. All plants were analysed using a combination of FISH with the repetitive probes and GISH that allowed identification of all chromosomes and the construction of detailed karyotypes. In addition, identification of the recombinant chromosomes revealed which of the chromosomes of A. aurea and A. inodora were actually homoeologous.The recombinant chromosomes showed a large number of recombination points, indicating that multiple crossovers had occurred. The distribution of the recombination points indicated that chiasmata are formed along the entire length of the chromosomes. Furthermore, the analysis of recombinant chromosomes revealed structural differences (one translocation and one inversion) between two sets of homoeologous chromosomes. These differences were confirmed by analysis of metaphase I configurations of these chromosomes in the hybrid and the BC1 plants (Chapters 4 and 5).The detailed analysis of the genome constitution of the plants revealed two different types of plants, near diploids (2n=2x+1=17) and triploids (2n=3x=24), indicating that two different types of gametes were functional in the hybrid, viz., n- and 2n-gametes. The GISH and FISH analysis provided evidence that 2n-gametes were functional both from male and female parents and had originated in all cases through a mechanism genetically leading to first division restitution (FDR) (Chapter 4).In order to investigate the fate of the introgressed A. aurea segments in A. inodora , meiosis was analysed using GISH and FISH in the triploid BC1 plants. These plants contained two more or less complete genomes of A. inodora and one of A. aurea as a result of the FDR mechanism (Chapter 4). Metaphase I configurations were studied per set of three homo(eo)logous chromosomes. This analysis revealed, as expected, preferential pairing of the A. inodora chromosomes, whereas the A. aurea chromosomes usually were unpaired. Only low frequencies of homoeologous chromosome pairing were observed, which is in contrast to what was found in the parental hybrid. Interestingly, the recombinant chromosomes generally formed trivalents with their two homo(eo)logues. These chromosomes were only associated at homologous (recombinant) chromosome segments. At later stages of meiosis, normal distribution of the A. inodora chromosomes and the recombinant chromosomes into the gametes was observed, whereas the non-recombinant A. aurea chromosomes were randomly distributed among the gametes, pointing towards the perspective for obtaining addition lines or introgression of alien chromosome segments in Alstroemeria .For breeding, the most important observation, which was made in this molecular cytogenetic study of Alstroemeria , was the high frequency of pairing and recombination between homoeologous chromosomes in the interspecific hybrid and the almost absence of this phenomenon in the further backcross generations. In these backcrosses, preferential pairing between homologous chromosomes was observed. For efficient introgression breeding more emphasis should be given to the production of sufficient BC1 plants and the detection of desired recombinants in this generation.</p

Genetic diversity of proprietary inbred lines of sunflower, determined by mapped SSR markers and total protein analysis.

Thesis (Ph.D)-University of KwaZulu-Natal, Pietermaritzburg, 2008.This study compared DNA based SSR markers with total seed protein markers, used to evaluate genetic diversity of sunflower. The multiplex-ability, cost effectiveness and applicability of microsatellites as molecular markers for a genetic diversity study were investigated and evaluated based on pedigree data of the sunflower germplasm. A solution for oil and fat interference in ultrathin iso-electric focusing gels was investigated, in order to make imaging and interpretation easier and clearer. Total protein analysis was utilized for the determination of genetic diversity on the same inbred material used for the DNA analysis. Finally a correlation is made between the data obtained on DNA vs Protein compared with phenotype and expected pedigree data. A set of 73 SSR markers with known mapped positions were utilized to determine genetic similarity in a group of sunflower inbred lines. Cluster analysis of genetic similarity revealed an excellent correlation with the breeding background and source information obtained from breeders on all inbred lines used in this study. Cluster analysis gave a clear differentiation between B and R-lines, showing clearly defined heterotic groups of the proprietary set of inbred lines. The most outstanding single-locus SSR markers in the set used for this study were identified and used as a core set. Multiplex assays were designed and optimized for the most cost and time effective method for rapid variety identification. The selected markers produced robust PCR products, amplified a single locus each, were polymorphic among the elite inbred lines and supplied a good, genome-wide framework of completely co-dominant, single-locus DNA markers for molecular breeding. The use of a fluorescent-tailed primer technique resulted in a considerable cost saving. Furthermore, the SSR markers can be multiplexed through optimization, in order to avoid undesirable primer-primer interactions and non-specific amplification. First stage iso-electric focusing of total protein extracts were used to analyze sunflower looking at genetic purity and genetic variety verification on diverse sunflower germplasm. Severe visual interference was visible on most seed storage protein extracts of sunflower. This interference was visible as a distortion in the gel matrix on the anodal end of the gel, and caused important proteins to denature in the presence of heightened field strength and the absence of a uniform matrix. Adjustment of the extraction solutions removed this interference. Total protein profiles were generated with the use ultrathin layer iso-electric focusing (UTLIEF) to assess the level of genetic diversity on the same set of sunflower lines used for the SSR analysis. Finally, the genetic diversity of the sunflower germplasm was analysed by comparing proteomic, genomic and pedigree data from the same germplasm. A total of 295 alleles were amplified with a set of 73 SSR markers with known mapped positions. These were utilized to determine the genetic relatedness of a group of B-lines and R-lines of sunflower. In parallel, a total of 68 protein bands were visualized using protein samples of two types of seed storage proteins derived from exactly the same sunflower lines. Cluster analysis clearly differentiated between the B-lines and R-lines, identifying defined heterotic groups of this proprietary set of lines. The comparison of DNA and protein data for the application of genetic diversity studies is analysed, as well as the general comparison on the use of the two different molecules as markers

Interspecific Hybridization in Plant Biology

Many crop gene pools are derived from a small number of founders. As a consequence of long histories of strong directional selection, crop gene pools have narrow genetic diversity available to provide inherent solutions to changing needs or challenges. Notoriously, plants can mate across taxonomically-determined species boundaries, and interspecific hybridization is widely used in plant genetics research. Interspecific hybridizations have conferred practical improvements to crops, some of which are unexpected based on the phenotypes of the parents. Genomics has provided insights into the fundamental consequences of interspecific hybridization for plant biology. Additionally, genomics has allowed the development of molecular tools for dissecting the genetic control of phenotypic variation in interspecific hybrid populations and manipulating interspecific introgressions in crop improvement. This Research Topic aims to publish peer-reviewed research to interspecific hybridization and its consequences, both fundamental and applied. While such work is prominent in plants, consideration will also be given to salient work in other taxa. A key threshold for publication will be the extent to which findings are of cross-cutting interest and importance, i.e. not only to those working on the target taxon but to a wide range of biological scientists.Peer reviewe

Aspects of the visual arts in advertising with particular reference to South Africa.

Thesis (M.A.)-University of Natal,1998.This investigation accepts that art is a term of western culture and that advertising is a creation of an historical and social process firmly linked to the economies of western industrialised nations. A cultural niche theory of the visual arts is employed to define the various visual art forms and it is in this context that the development of the notion of fine art, which had its origins during the Renaissance, is investigated with a view to how this led to the commodification of art. The phenomenon of art as a commodity accelerated throughout the nineteenth century and was moulded by the same political, cultural, social, economic and technological forces that gave rise to advertising when, during the second half of the century, the capitalist system of production became geared towards mass production of products for consumption. This was also the period of significant European colonial expansion in southern Afiica and consequently the development of both art and advertising in the region was cast in a colonial, European mould, the effects of which are investigated throughout this research project. This body of research also seeks to explain how the meaning and the value of the art object and its reproduced image, changed and became exchangeable as technology developed. Significantly this occurred at a time when the needs of advertising shifted from a simple system of proclamation and announcement on the periphery of the national economy during the nineteenth century to become a sophisticated system of communication which acts as an influential social institution at the end of this millennium. That this appears to have occurred at a time when the influence of fine art began to decline as a cultural force is significant as it is in this context that advertising has become a primary carrier of meaning in society. This research project works within this paradigm to investigate the history and motives of business support for the arts, particularly the visual arts, in the form of sponsorship with particular reference to a culturally diverse and politically dynamic South Africa. In addition, specific rhetorical devices that advertising employs, as a strategic tool of marketing, to appropriate and (ex)change meaning from the value laden visual art object is investigated with reference to contemporary advertising in South Africa