Thesis (Ph. D.)--University of Missouri-Columbia, 1997. / Typescript. Vita. Includes bibliographical references (leaves 405-414). Also available on the Internet.

Thesis (M.Sc.(Zoology and Entomology))--University of Pretoria, 2008. / Summary in English. Includes bibliographical references.

No description available.

No description available.

Thesis (MSc)--University of Stellenbosch, 2000. / ENGLISH ABSTRACT: Streptomyces spp. are responsible for a large proportion of the world-wide quality deterioration of potatoes causing a potato tuber disease called cornmon scab. Determining the genetic diversity of the Streptomyces spp., especially the main pathogen, S. scabies, has been a prerequisite for the ultimate control of common scab. Techniques responsible for the classification and determination of genetic diversity have improved with advances in DNA technology. Analysis of South African (S.A.) S. scabies isolates has been focusing on the organisms' morphology, physiology, pathogenicity and melanin production, but the classification of S. scabies using DNA techniques has not yet been explored. In this study various DNA techniques were screened for optimal use in determining the genetic diversity within and among isolates of S. scabies. Bacteria had been sampled from the main potato producing regions in S.A. and a few other regions. The techniques explored included RAPDs, AFLPs, RAMS, Rep-PCR, 16S rDNA sequencing and ITS analysis. The first three techniques had to be abandoned due to non-reproducibility between the same isolate extracted on separate occasions and ITS analysis was abandoned due to sequencing difficulties. Of the three Rep-PCR techniques tested (BOX, ERIC and REP), BOX was selected because it produced the clearest and most reproducible results. BOX-PCR and 16S rDNA sequencing were therefore ultimately selected as the methods to analyse the genetic diversity of the S. scabies isolates. Information concerning the pathogenicity of the isolates was supplied by the Vegetable and Ornamental Plant Research Institute of the Agricultural Research Council (VOPI, ARC, Roodeplaat). A brief analysis of the pathogenicity prediction of the isolates in this study was explored with the PCR technique. Presence of the necJ gene was previously shown to be an indication of the pathogenicity within the Streptomyces spp. group. PCR analysis is based on the amplification of a O.72kb fragment (necl) in pathogenic isolates which was absent in non-pathogenic isolates. However, in this study the test for pathogenicity lacked specificity and sensitivity and some of the problems experienced included non-reproducibility between PCR reactions and the presence of the pathogenic fragment in the nonpathogenic isolates (as designated by VOPI, ARC). These observations led to the conclusion that this technique is not an ultimate test for pathogenicity of S. scabies isolates in a South African context. The genetic distances and similarity matrices of the Rep-PCR results were calculated using Nei's genetic distance calculation (Nei M, 1975). Clusters from these matrices were constructed using the unweighted pair group average (UPGMA) with the PAUP4 package. The clusters for the 16S rDNA sequences were formed with the Neighbor Joining (NJ) method and the PAUP4 package. The NJ trees do not take small sequencing differences into account, therefore a Parsimony Network had to be constructed. The trees obtained with the 16S rDNA sequencing techniques grouped most S. scabies isolates into one major group with a 100% bootstrap robustness of this group. More genetic diversity was illustrated by the BOX-PCR technique and the isolates were generally grouped according to their different regions of origin. However, the bootstrap values were low, indicating a lack of robustness regarding the BOXPCR clustering. This was not unexpected as the number of data points employed in the BOX technique is very limited. Both techniques revealed unexpected grouping of a few isolates. Their isolated positions could be attributed to possible misclassification or to the fact that they could be genetically different S. scabies isolates. Streptomyces spp. (other than S. scabies) displayed enough differences to place them in their own distinct groups using both techniques. Comparison of the cluster results obtained in this study did not correlate to the data supplied by the VOPI, ARC (morphology, physiology, pathogenicity and melanin production) which revealed differences between the S. scabies isolates within their respective regions. The lack of diversity displayed by the 16S rDNA technique can be attributed to the fact that only a limited section of the genome is involved making it inappropriate for intra-species genetic diversity analysis. The BOX technique takes various loci within the genome but is still not ideal for a thorough genetic diversity analysis. This study represents the first attempt to determine the genetic diversity of S. scabies in S.A. on DNA level. / AFRIKAANSE OPSOMMING: Streptomyces spp. is verantwoordelik vir 'n _groot deel van die wereld afname in aartappel kwaliteit as gevolg van die aartappelknol siekte bruinskurf. Die bepaling van die genetiese diversiteit tussen die Streptomyces spp., varal die hoof patogeen in die groep, S. scabies, is 'n vooreiste vir die uiteindelike beheer van bruinskurf. Tegnieke verantwoordelik vir die klassifikasie en bepaling van genetiese diversiteit het verbeter met vooruitgang in DNA tegnologie. Analise van Suid Afrika (S.A.) se S. scabies isolate konsentreer op die organisme se morfologie, fisiologie, patogenisiteit en malanien produksie, maar die klassifikasie van S. scabies met die behulp van DNA tegnieke is nog nie uitgevoer me. In hierdie studie is verskeie DNA tegnieke ondersoek vir optimale bepaling van genetiese diversiteit binne en tussen S. scabies isolate van S.A Bakteriee is verkry van die hoof aartappel-produserende areas in S.A. en ook van 'n paar ander areas. Die tegnieke wat in die studie gebruik is, het RAPDs, AFLPs, Rep-PKR, 16S rDNA volgordebepaling en ITS analise ingesluit. Die eersgenoemde drie tegnieke is uitgesluit as gevolg van nie-herhalende resultate tussen dieselfde isolaat geisoleer op verskillende geleenthede. ITS analise is uitgesluit as gevolg van probleme met volgordebepaling. Rep- PKR en 16S rDNA volgordebepaling is uiteindelik gekies as die mees geskikte metodes vir die analise van genetiese diversiteit tussen S. scabies isolate in hierdie studie omdat albei skynbare herhaalbare resultate gelewer het. Inligting met betrekking tot die patogenisiteit van die isolate is voorsien deur die Groente en Sierplant Instituut van die Landbou Navorsinsraad (YOPI, LNR). 'n Vinnige analise van die patogenisiteits voorspelling van die isolate is uitgevoer met die PKR tegniek. Dit is voorheen aangetoon dat die teenwoordiheid van die necJ geen dui op die patogenisiteit in die Streptomyces sp _groep. PKR analise het 'n O.72kb fragment (necl) in patogeniese isolate geamplifiseer wat nie teenwoordig was in niepatogeniese isolate nie. Hierdie toets vir patogenisiteit soos gebruik in hierdie studie was egter onspesifiek en onsensitief en sommige van die probleme wat ondervind is sluit in nie-herhaalbaarheid tussen PKR reaksies en die teenwoordigheid van die patogeniese fragment in die nie-patogeniese isolaat (soos beskryf deur YOPI, LNR). Uit hierdie waarnemings word afgelei dat die tegniek nie 'n geskikte toets vir patogenisiteit van S. scabies isolate in 'n S.A konteks is nie. Die genetiese afstande en ooreenkomstige matrikse van die Rep-PCR resultate is bereken met die genetiese afstand bepaling van Nei (Nei M, 1975). Groepe is gevorm met die "unweighted pair group average" (UPGMA) en PAUP4 pakket. Die "Neighbor Joining" (NJ) groepe is gevorm met die 16S rDNA volgordebepaling data mbv die PAUP4 pakket. Die NJ groepering neem nie klein volgorde verskille in ag nie en gevolglik moes'n "Parsimony Network" opgestel word. Die groepering met die 16S rDNA volgordebepaling het meeste van die isolate in een hoof groep geplaas met 'n 100% "bootstrap" waarde. Meer genetiese diversiteit is met die BOX-PCR tegniek gevind en isolate was oor die algemeen gegroepeer vol gens van hul oorsprong. Die "bootstrap" waardes vir die BOX tegniek was baie laag. Dit was nie onverwags nie, want die hoeveelheid data punte was beperk met die BOX tegniek. Albei tegnieke het 'n aantal afwykende isolate vertoon. Hul ge-isoleerde posisies kan toegeskryf word aan moontlike misklassifikasies van die isolaat. Die moontlikheid dat daar wel genetiese verkille tussen die isolate is, kan egter nie uitgesluit word nie. Streptomyces spp. (uitgesluit S. scabies) het genoeg variasie vertoon om hulle in hul eie groepe met die gebruik van beide tegnieke te plaas. Vergelyking tussen die groepe in die studie stem nie ooreen met die data verkry vanaf YOPl, LNR (morfologie, fisiologie, patogenesiteit en melanien produksie) nie wat verskille tussen S. scabies isolate binne 'n sekere gebied vertoon. Die gebrek aan diversiteit soos vertoon deur die 16S rDNA tegniek kan toegeskryf word aan die feit dat slegs 'n beperkte gedeelte van die genoom ondersoek word, wat dit ongeskik vir intra-species genetiese diversiteit analise maak. Die BOX tegniek neem verskeie loci in die genoom in ag, maar is steeds nie ideaal vir deeglike genetiese diversiteit analise nie. Hierdie studie verteenwoordig die eerste poging om die genetiese diversiteit van S. scabies in S.A. op DNA vlak te bepaal.

The aim of the thesis was focused on assessing the significance of the impact of habitat on the occurrence of the common scab of potatoes. In this context, following factors were evaluated: degree and extent of infestation tubers with common scab, effect of the habitat, impact of the variety, vintage influence, the influence of fertilization with nitrogen and sulfur influence seed treatment, starch content, tuber yield, the proportion of tubers over 40 mm. The review of literature of thesis includes chapters regarding the origin of potato, potato and morphological characteristics of its growth, consumer potatoes and factors that affect the quality and yield. It mentions measures against diseases and pests. The last section is devoted to common scab of potato. The practical part deals with evaluating the impact of habitat on the incidence of common scab of potatoes. The attempt was based on the habitat with the occurrence of common scab and habitats without occurrence of common scab in Vyklantice. The results were processed in program Statistica, version 12.0. (StatSoft) function of multifactor and one-way analysis of variance (ANOVA). At the habitat with higher pH and KVK higher incidence of common scab was recorded. It confirmed the impact of resistance of variety on the incidence of common scab. It was not confirmed statistically significant dependence on fertilizer nitrogen fertilizer LAV and seed treatment tubers with Trichoderma strains. It confirmed a statistically significant dependence on the incidence of common scab on fertilization with SulfoGranulat.

Made available in DSpace on 2014-06-11T19:26:47Z (GMT). No. of bitstreams: 0 Previous issue date: 2003-01-31Bitstream added on 2014-06-13T19:34:38Z : No. of bitstreams: 1 bacagarcia_cj_me_botfca.pdf: 686283 bytes, checksum: 9f5d82436241ea9ddad7462757ebd1ba (MD5) / A batata é uma cultura que tem desenvolvimento e produtividade intensamente influenciados pelas condições de umidade do solo, assim, o controle da umidade do solo é decisivo para o êxito desta cultura. O presente trabalho de pesquisa foi conduzido em área aberta, de agosto a novembro do ano 2001, no Departamento de Engenharia Rural da Faculdade de Ciências Agronômicas da Universidade Estadual Paulista, Botucatu-SP, objetivando avaliar os efeitos da irrigação por gotejamento superficial e subsuperficial associadas a fertirrigação e dois tipos de plantio na produtividade de batata, cultivar Aracy (IAC-2). O delineamento experimental utilizado foi em blocos ao ocaso em esquema fatorial 22, com 2 sistemas de irrigação: Irrigação por gotejamento, superficial e subsuperficial; 2 sistemas de plantio: Plantio Tradicional (PT), e Fileiras Duplas (FD); com 5 repetições perfazendo um total de vinte parcelas. A parcela experimental do tipo PT teve uma área útil de 7,2m2 e o tipo FD 6,0m2. O tubo gotejador, nos tratamentos de irrigação por gotejamento subsuperficial, foi enterrado a uma profundidade de 0,30m. Verificou-se na irrigação por gotejamento superficial, que utilizando uma pressão de 70kPa, a vazão média por gotejador foi de 0,68L.h-1, e a uniformidade de distribuição da água do sistema de 94,65%. O valor médio de consumo total de água foi de 218,29mm, o que correspondeu a um consumo médio de 2,30mm.dia-1 durante o ciclo da cultura. Após a colheita avaliou-se a produção total comercial obtendo-se uma produtividade média de 32,51t.ha-1, os tratamentos revelaram uma produtividade média de 30,46; 32,03; 33,46; e34,09t.ha-1, para T1(Plantio tradicional e irrigação por gotejamento superficial), T2(Plantio tradicional e irrigação por gotejamento subsuperficial), T3(Plantio fileira dupla e irrigação por gotejamento superficial) e T4... . / The potato is a crop that has development and high productivity influenced by the ground humidity conditions, thus, the humidity control of the ground is decisive for the success of this crop. The present work, was conducted in a opened area, from august to november of 2001, at the Department of Agricultural Engineering of the Faculdade de Ciências Agrárias- UNESP/Botucatu-SP, aiming to evaluate the effect of the irrigation for superficial and subsurface dripping associated to the fertirrigation and two types of plantation on the potato productivity, cultivar Aracy (IAC-2). The experimental delineation was experimental blocks in factorial project type 22, with 2 irrigation systems: Dripping, superficial and subsurface; 2 systems of plantation: Traditional Plantation (PT), and Double Lines (FD); with 5 repetitions totalizing twenty parcels. The PT experimental parcel had a useful area of 7,2m2 and FD type 6,0m2. The trickle pipe in the irrigation treatments for subsurface dripping, was buried to a depth of 0,30m. It was verified that the irrigation for superficial dripping, using a pressure of 70 kPa, the trickle average outflow of 0,68L.h-1, and the water distribution uniformity system of 94,65%. The average of total water consumption was of 218,29mm, with corresponded to an average consumption of 2,30 mm during the cycle of the culture. After the harvest the average total commercial production evaluated was 32,51t ha-1, the treatments revealed an average productivity of 30,46; 32,03; 33,46; and 34,09t.ha-1, for T1, T2, T3 and T4, respectively. It had a trend for bigger productivities when the plantation was carried through in FD system, when compared with the PT, with a difference of 8,1%. The total average production of bulbs dry matter was of 20,87 %. The results indicate that the productivity of this crop, were influenced by the double lines plantation system and by the density of... (Complete abstract, click electronic address below).

Resumo: O presente trabalho de pesquisa teve por objetivo avaliar a influência da aplicação de silício na nutrição, tolerância ao déficit hídrico e nas características relacionadas à produtividade da cultura da batata (Solanum Tuberosun L.) cv Bintje. Os tratamentos foram constituídos da combinação da presença e ausência de aplicação de silício (0 e 283 Kg ha-1 de Si), por meio da coreeção do solo com calcário dolomítico e silicato de cálcio e magnésio, e presença e ausência de déficit hídrico (-0,020MPa e -0,050MPa de tensão de água no solo, respectivamente). O delineamento experimental foi inteiramente casualizado, num arranjo fatorial de 2x2, com oito repetições. Cada parcela experimental foi constituída de uma planta de batata cultivada em vaso com 50 litros de solo. O controle da irrigação foi realizado com auxilio de tensiômetros de mercúrio. A presença de maiores quantidade de silício solúvel no solo promoveu uma maior absorção de fósforo pelas plantas e aumento do teor de silício nas folhas e tubérculos. O fornecimento de silício na ose de 283 kg ha-1, mediante a aplicação do corretivo agrosilício como substituto do calcário na cultura da batata, promoveu benefícios à cultura proporcionando redução do acamamento em função de hastes mais eretas, maior altura de plantas, aumento no peso médio dos tubérculos e conseqüente aumento da produção comercial e total. os teores de prolina aumentaram e os de açúcares solúveis totais diminuiram em função da meno disponibilidade hídrica e da maior disponibilidade de silício no solo. O silício promoveu a desroção de fósfor no solo aumentando a quantidade do elemento disponível para as plantas. O corretivo agrosilício utilizado como fonte de silício proporcionou os mesmos níveis de correção e de fornecimento de cálcio e magnésio que o calcário, podendo ser utilizado em substituição do mesmo. / Abstract: The aim of this study was to evaluate the influence of silicon application on potato plant, productivity and resistance to water stress. The treatments was the presence abd absence of silicon combination (0 and 283 kg ha-1 of Si), by liming with calcium carbinate and silicate, and presence and absence of water stress (- 0,020MPa and - 0,50MPa of water tension, respectively). The experimental was a cpmpletely randomized design with 2x2 factorial arrangement and 8 replications. Each experimental plot was consisted of a cultivar Bintje potato palnt (Solanum tuberosum) planted en a 50-liter lot. mercury tensiometers were used for the irrigation control. The presence of higher soluble silicon in the soil increase phosphorus uptake in plants and increase the content of silicon in leaves and tubers. The silicon application of 283 kg ha-1 using silicate provide benefits to the potato crop improving plant architecture by erets stems, increase on plant height, increase tubers weight average and commercial and total yield. the prolina content had increased and the total soluble sugars decresed with the water stress and higher silicon content in the soil. The silicon fertilization provided increase available phosphorus in the soil and uptake by the plants. The agrosilício material could be use as lime because it has the equability to increase Ca and Mg and have approximately same effect on soil pH and base saturation. / Orientador: Leandro Borges Lemos / Coorientador: Carlos Alexandre Costa Crusciol / Banca: Roberto Lyra Villas Bôas / Banca: Gaspar Henrique Korndörfer / Mestre

The aim of my diploma thesis was to evaluate four densities of growth by chosen varieties of potatoes. The thesis deals with the experiment on 4 different varieties of potatoes. I have chosen the standard technology of growing ware potatoes. The selected densities of growth were 35 000, 40 000, 45 000 and 50 000 young plants ha-1. Each variant was repeated four times. I have evaluated the yield of bulbs, the share and yield of ware bulbs, the average number of bulbs for one plant, the weight of bulbs for one plant, the average weight of a bulb and the average weight of ware bulbs. The research was done on a private farm like the field experiment. The farm is located in potato-growing area in Vysočina Region, 490 metres above the sea level. Potatoes are grown approximately over 7 hectares on the farm. The experiment started in 2010. The potato planter MARS 42 was used for the planting. The distance between drills was 0,75 metre. Parcels consisted of 4 drills, each drill equals one repetition, each parcel equals one density of growth. On purchase of samples was realized the kickoff of 10 plants from each repetition. What followed was division of bulbs according to their size in each sample. They were divided into bulbs smaller than 40 millimetres and bigger. After that the samples were weighed and bulbs were counted. The number of bulbs and the weight of bulbs are very important for subtotal. It was established the variety Mirage made the best results when the density was 45 000 plants ha-1. The variety Agria had two suitable densities of growth, namely 40 000 and 45 000 plants ha-1. There was no considerable difference between them. In contrast with previous, the varieties Victoria and Marabel made the best result when the density was 35 000 plants ha-1. I have realized the density 50 000 plants ha-1 is explicitly unsuitable for all varieties. This density of growth is loss-making especially because of lowering of all assessed indexes. Another disadvantage is higher costs (more bulbs are required) and then there is also bigger risk of diseases and pests.

Potato (Solanum tuberosum) is one of the most popular food crops grown as a substitute staple in Zimbabwe. Its production is constrained by pest and diseases which reduce the yield drastically. The blackleg / soft rot disease complex caused by Pectobacterium and Dickeya species (formerly known as Erwinia) has been identified as a potential threat to potato production. The soft rot pathogens can cause systemic and vascular infections in potatoes, which result in the development of various symptoms on the stem and tubers. The symptoms that develop on the plant are not species specific but depend on climatic conditions prevailing at the infection stage. The pathogens affect the crop at all stages of production, which include in the field, storage and in transit. The primary objectives of this study were to identify the pathogens which cause blackleg and soft rot on potatoes in Zimbabwe; document the grower’s knowledge of blackleg and soft rot diseases in Zimbabwe; evaluate cultivars grown in Zimbabwe and South Africa for tolerance to Pectobacterium and Dickeya species; determine the role of calcium in blackleg and soft rot development; and determine the genetic diversity of Pectobacterium carotovorum subsp. brasiliensis isolates from South Africa, Zimbabwe and mini-tubers imported from China. The first chapter introduces the research highlighting the importance of potatoes globally and in Zimbabwe. It discusses production constraints caused by soft rot pathogens, as well as the pathogenesis of Pectobacterium and Dickeya spp. It also summarises the research objectives and thesis outline. Chapter 2 provides an overview of published literature on morphology, pathogenicity and identification of blackleg and soft rot pathogens, epidemiology, host range, defense mechanisms in plants, host nutrition and disease management strategies. Taxonomic revisions have led to the reclassification of pectolytic Erwinia into several genera. Strains formerly described as Erwinia carotovora have been incorporated into the genus Pectobacterium, and strains classified as Erwinia chrysanthemi are now assigned to the genus Dickeya. Several species and subspecies of Pectobacterium and Dickeya have isolated from infected potatoes. In Zimbabwe only Pectobacterium atrosepticum and Pectobacterium carotovorum subsp. carotovorum have until now been identified as the causal agents of blackleg and soft rot diseases, respectively. Although other species and subspecies of Pectobacterium and Dickeya have been isolated from infected potato plants in Zimbabwe, their potential to cause diseases on potatoes should not be underestimated. In chapter 3 bacterial isolates collected from infected plants showing typical blackleg / soft rot disease symptoms were identified using biochemical and physiological methods, as well as rep-PCR, Amplified Fragment Length Polymorphism (AFLP) and single gene sequencing using two genes, viz. gyrB and recA. Amplified Fragment Length Polymorphisms (AFLPs) were used to study the genetic diversity among potato isolates from Zimbabwe, South Africa and mini-tubers imported from China. Pectobacterium and Dickeya species enter the plant through wounds and natural openings such as lenticels. When they invade the plant they colonise the vascular tissue and spaces between the thin walled parenchyma cells. They remain inside these cells as latent infections and disease symptoms develop when host resistance is impaired or when environmental conditions become conducive for disease development. Chapter 4 investigates the role of defense related enzymes, polyphenol oxidase, phenylalanine ammonia lyase, peroxidases, chlorogenic acid and total soluble phenols in host resistance to potato soft rot. The potato varieties were assayed for activity of polyphenol oxidase and phenylalanine ammonia lyase, peroxidases and concentration of chlorogenic acid and total soluble phenols in tuber tissue. The role of these four components in imparting resistance against the soft rot pathogens was also investigated. Blackleg and soft rot diseases are seed-borne and difficult to control using chemical, physical and cultural methods. Several approaches aimed at controlling blackleg and tuber rot have been studied but the degree of success has been variable. Plant nutrition is an important component of natural disease resistance. The effect of calcium soil amendments in enhancing resistance to potato soft rot pathogens was investigated in Chapter 5. A management strategy based on calcium-induced defense responses of potato to Pectobacterium and Dickeya spp. was investigated. Calcium promotes production of phenolics and strengthens the cell wall, making the plants resistant to maceration by pectolytic enzymes. In Chapter 6 a survey was conducted in nine potato growing regions of Zimbabwe using an informal structured questionnaire. The findings highlighted the distribution and impact of blackleg and soft rot diseases on the Zimbabwean potato industry. A broad spectrum of information on blackleg / soft rot disease complex was gathered and this information can help growers to make informed decisions about control strategies to apply. Each chapter in this thesis has been treated as an independent entity. Thus redundancy between chapters could not be avoided. It is my hope that the results of these studies on soft rot pathogens in Zimbabwe will contribute to a better understanding of the blackleg / soft rot disease complex that they cause. I also hope that these studies will form the basis of detailed and future investigations in epidemiology and disease control strategies. / Thesis (PhD)--University of Pretoria, 2012. / Microbiology and Plant Pathology / unrestricted