Gray mold, caused by Botrytis cinerea is the major cause of postharvest loss in strawberries. Detection of flower and fruit infections enables producers to make intelligent management decisions. A plate-trapped ELISA protocol using a Botrytis-specific monoclonal antibody (BC-12.CA4) was developed for the detection of Botrytis cinerea in strawberry flower receptacles and red fruits. Horseradish peroxidase, was chosen as enzyme conjugate because it gave lower background absorbance in disease-free samples. B. cinerea reference antigen (RAg) was isolated from strawberry. BC-12.CA4 was very sensitive to the RAg, detecting up to 6 mug/ml of RAg when mixed with strawberry extracts. The MAb did not show any reaction to Rhizopus sp., Mucor sp. and Penicillium sp. associated with strawberry. B. cinerea could be detected in receptacles two days after inoculation. Treatment of inoculated receptacles with paraquat speeded-up detection. Inoculated red fruit infection could be detected after three days of incubation. Disease in commercially-produced receptacles and red fruits were assessed visually and by ELISA. The ELISA detected B. cinerea in 95% of commercial flower samples, whereas the traditional visual method detected only 50 to 70%. No dramatic differences between methods were found for red fruits.

Thesis (Ph. D.)--University of Alberta, 2009. / Title from pdf file main screen (viewed on June 29, 2009). "A thesis submitted to the Faculty of Graduate Studies and Research in partial fulfillment of the requirements for the degree of Doctor of Philosophy Plant Science, Department of Agricultural, Food and Nutritional Science, University of Alberta." Includes bibliographical references.

Thesis (Ph.D.) - University of KwaZulu-Natal, Pietermaritzburg, 2007. / Full text also available online. Scroll down for electronic link.

Thesis (M.Sc.) - University of KwaZulu-Natal, Pietermaritzburg, 2007. / Full text also available online. Scroll down for electronic link.

Thesis (MScAgric)--Stellenbosch University, 2012. / ENGLISH ABSTRACT: Leaf blackening, a postharvest disorder which is characterized by a dark brown to black discoloration, is found in most commercially important Protea cut flower species and cultivars. As this disorder is known to increase with storage time, it is a major concern to the South African industry as the use of sea freight is increasingly preferred due to lower transport costs and a more favourable carbon footprint. The cause of leaf blackening has been strongly linked to a carbohydrate stress exerted by the large inflorescence, thus requiring the utilization of sugar bound polyphenols in the foliage, which when removed, can oxidize enzymatically or non-enzymatically. A study where harvesting was done throughout the season as well as on selected days at 08:00, 12:00, 15:00 and 17:00, concluded that leaf blackening incidences in Protea cv. Sylvia stems varies significantly throughout the season, between years and even with the harvest time of day. Leaf blackening incidences increased from October onwards and remained high until February, before decreasing to acceptably lower levels towards March to May. Carbohydrate- and phenolic content together with water status of leaves at harvest was not able to accurately predict incidence of the associated leaf blackening. However, irrespective of the season of harvesting, leaf blackening was significantly lower when stems were harvested later in the day than compared to stems harvested in the morning. Low sucrose and high water content at these harvest times was positively correlated to high incidences of leaf blackening. In a next study where uptake dynamics of glucose pulsing was investigated, Protea cv. Sylvia was harvested at different times throughout the day, dehydrated to various levels and pulsed with an increasing range of glucose concentrations. Pulsing solution uptake per stem was found to be highly influenced by these factors, as dehydration of stems and a harvest time later during the day both decreased stem water potential, which then increased pulse-solution uptake within a certain time period. The daily harvest time influenced transpiration, whilst pulse-solution uptake decreased with an increase in glucose pulse concentration. When stems were pulsed pre-storage with an increasing range of glucose concentrations, not only did pulses of between 4.7 – 13.7% glucose significantly delayed the incidence of leaf blackening, but it also maintained a positive water balance longer in stems during vase life. Ethanol or acetaldehyde vapour did not provide a viable alternative for reducing leaf blackening incidence in Protea cv. Sylvia, although a synergistic effect was found when ethanol vapour or pulsing was used in combination with glucose. A commercial verification trial disclosed that Protea magnifica and Protea ‘Pink Ice’ reacted more beneficial to ethanol vapour than was observed in ‘Sylvia’. This study confirms that carbohydrate availability within the Protea cut stem remains a key factor in the control of leaf blackening. Factors which assist in maintaining high internal carbohydrate levels, such as enhanced glucose pulse uptake or effective vase solution utilization will contribute to providing an optimum control of leaf blackening during vase life following long-term cold storage. / AFRIKAANSE OPSOMMING: Loofblaarverbruining is ‘n na-oes defek wat gekarakteriseer word deur ‘n donker bruin na swart verkleuring wat voorkom in meeste kommersieël belangrike Protea snyblom spesies en kultivars. Hierdie defek is bekend daarvoor dat dit toeneem met stoortyd, dus is dit ‘n groot kommer vir die Suid-Afrikaanse industrie, met toenemende gebruik van seevrag as vervoer keuse wat laer vervoer kostes en meer gunstige ‘koolstof voetspoor’ bevoordeel. Die oorsaak van loofblaarverbruining word sterk gekoppel aan ‘n koolhidraat stres wat uitgeoefen word deur die groot bloeiwyse op die loofblare, waar suiker-gebonde polifenoliese verbindings ensiematies of nieensiematies geoksideer word met die verwydering van die suiker verbinding. 'n Studie waar geoes was regdeur die seisoen, sowel as op geselekteerde dae om 08:00, 12:00, 15:00 en 17:00, het bevind dat die voorkoms van loofblaarverbruining in stele van Protea kv. Sylvia aansienlik geskil regdeur die seisoen, tussen jare en selfs met die oes tyd gedurende die dag. Die voorkoms van loofblaarverbruining het toegeneem vanaf Oktober en het hoog gebly tot en met Februarie, voordat dit gedaal het tot aanvaarbare laer vlakke teen Maart, tot en met Mei. Koolhidraat-en fenoliese inhoud sowel as die water status van die blare by oes was onsuksesvol om die voorkoms van die gepaardgaande loofblaarverbruining akkuraat te voorspel. Loofblaarverbruining was egter aansienlik laer as stele geoes later in die dag teenoor stele geoes in die oggend, ongeag die seisoen van oes. Lae sukrose en 'n hoë water inhoud geassosieer met hierdie oes-tye was positief gekorreleerd met ‘n hoë voorkoms van loofblaarverbruining. In 'n volgende studie waar die opname dinamika van glukose pulsing ondersoek was, is Protea kv. Sylvia stele geoes op verskillende tye dwarsdeur die dag, gedehidreer tot verskillende vlakke en met 'n toenemende reeks van glukose konsentrasies gepuls. Pulsoplossing opname per steel is sterk beïnvloed deur hierdie faktore, aangesien dehidrasie van die stele asook stele geoes later gedurende die dag die afname van steel waterpotensiaal veroorsaak het, terwyl die puls-oplossing opname versnel het binne ‘n bepaalde tyd. Die tyd van oes beïnvloed ook transpirasie, terwyl vaas oplossing opname afgeneem met 'n toename in glukose puls konsentrasie. Wanneer ‘Sylvia’ stele gepuls was voor stoor met 'n reeks van toenemende glukose konsentrasies, het nie net die puls van tussen 4.7 – 13.7% glukose aansienlik die voorkoms van loofblaarverbruining vertraag nie, maar dit het ook ‘n positiewe water balans langer in stele gedurende die vaas lewe behou. Nie etanol of asetaldehied dampe is bevind as geskikte alternatief vir glukose pulsing om die voorkoms van loofblaarverbruining in Protea kv. Sylvia te verlaag nie, alhoewel ‘n sinergistiese effek waargeneem was wanneer etanol in kombinasie met glukose gebruik was. ‘n Kommersieële bevestigingstoetsing het bevind dat Protea magnifica en ‘Pink Ice’ meer voordeel uit ‘n ethanoldamp behandeling kon trek teenoor ‘Sylvia’. Hierdie studie het bevestig die belangrikheid van koolhidraat beskikbaarheid in die Protea snyblom, vir beheer van loofblaarverbruining. Faktore wat die handhawing van hoë interne koolhidrate vlakke, soos bevorderde glukose puls opname of effektiewe vaas oplossing benutting sal bydra tot ‘n optimal beheer van loofblaarverbruining tydens vaas lewe na langtermyn koueopberging. / National Research Fund (NRF) for their financial support in 2009; Protea Producers of South Africa (PPSA) and Productschap Tuinbouw (PT) as well as the Frank Batchelor Will Trust Grant for the financial support.

Submitted in partial fulfillment for the Degree of Master of Technology: Biotechnology, M. L. Sultan Technikon, 2002. / Fusarium species produce toxic mycotoxins that are known to exert adverse health effects in humans and animals. No attempts have been made to establish mycotoxin-producing capabilities of isolates of Fusarium species from bananas exhibiting symptoms of crown rot. Crown rot is one of the most serious post harvest problems in banana and the disease is caused by different fungal species, principally Fusarium species. Banana, which is of great economic significance in growing countries (i.e. Costa Rica, Cameroon, Ecuador) is seriously affected by crown rot and is a major cause of fruit loss / M

The fungus Diplodia maydis, (synonym Stenocarpella maydis (Berk)) is worldwide one of the most important cob rot pathogens of maize. The isolation of stenocarpin, a metabolite toxic to ducklings, from maize cultures of D. maydis as the 4,6-0-diacetate derivative and its structure elucidation has been reported in the literature. Detailed NMR studies established the structure as either (3S,4R,6R,7R)- or (3R,4R,6R,7R)-spiro[(4,6, 7-trihydroxy-7-methyl-8-oxo-5,6,7,8-tetrahydroisochromane)-3 ,2' -tetrahydrofuran]. The absolute configuration of the C(3) spiroacetal stereogenic center remained unknown. The aim of the synthetic studies described in this dissertation was to develop a synthetic methodology for the spiroacetal moiety present in stenocarpin in order to establish unambiguously the C(3) absolute configuration. Retrosynthetic analysis of stenocarpin identified two model compounds (5S,lOR)- and (5R,lOR)-1,6-dioxaspiro[4.5]dec-8-en-10-o1 as the synthetic target. In turn the retrosynthetic analysis of these model compounds led to commercially available L-arabinose as starting material. Two strategies, which differ in the timing for the formation of the spiroacetal moiety as well as the initial type of protecting groups, were employed in the development of the synthetic route. In the first route the spirocyclisation reaction of a benzyl protected intermediate followed by the syn elimination of the cis-diol group resulted in the formation of only the (5S, lOR) model compound. The use of the acetonide and TBDPS protecting groups from the outset of the synthetic route and once again a spirocyclisation reaction, led to the formation of two spiro compounds epimeric at the C(5) spiro stereogenic centre, which could be separated and transformed by a syn elimination of the cis-diol group to the two model compounds. The configuration of the spiroacetal intermediates formed in the two synthetic routes and the changes in conformation that occurred in each of the steps were deduced from extensive NMR studies and especially the NOE technique. The results established the 3S configuration for stenocarpin and provided a viable synthesis for the (5S,lOR)-l,6-dioxaspiro[4.5]dec-8-en-1O-ol model compound that is to be used in the total synthesis of stenocarpin. In the dissertation the results of the first steps in a total synthesis, a study on the epoxidation of the double bond, is presented. / Dissertation (MSc (Chemistry))--University of Pretoria, 2006. / Chemistry / unrestricted

Please read the abstract in the section 07back of this document / Dissertation (MSc (Plant Pathology))--University of Pretoria, 2006. / Microbiology and Plant Pathology / unrestricted

Please read the abstract (Summary) in the section 00front of this document / Dissertation (MSc (Botany))--University of Pretoria, 2007. / Plant Science / MSc / Unrestricted

The South African commercial forest industry is almost exclusively reliant on plantations of exotic trees, of which Eucalyptus spp. make up almost 50 %. Botryosphaeria spp. are important canker pathogens in these Eucalyptus plantations in South Africa. However, exotic plantations and their pathogens cannot be viewed separately from the related native flora. This study showed the importance of extending our knowledge on pathogens that occur on related native and exotic hosts, and which can pose a threat by cross infection between these host groups. In Chapter 1, a review of the literature concerning Botryosphaeria spp. that occur on Eucalyptus in its native range and exotic plantations is presented. It is clearly shown that Botryosphaeria spp. are important pathogens on Eucalyptus in exotic plantations worldwide, causing various symptoms on this host. Botryosphaeria spp. are also important canker pathogens in Eucalyptus plantations in South Africa. Traditional identification of this group of fungi, based on morphological characteristics, led to much confusion about their identity. However, in recent studies morphological characteristics were combined with DNA sequence data to distinguish and identify these fungi. Based on these data a few revisions have been done and new Botryosphaeria spp. were described on Eucalyptus. Botryosphaeria spp. recognised as pathogens on Eucalyptus in South Africa include B. dothidea, B. parva and B. eucalyptorum. Future studies should be focused on correct identification of Botryosphaeria spp. that occur on Eucalyptus, which is the first step towards preventing the spread of this group of pathogens and developing management strategies to control disease outbreaks. During the study on Botryosphaeria spp. on Syzygium cordatum, isolates of two Botryosphaeria spp. appeared to be undescribed. One of the undescribed species was represented by only one isolate and it was not named. The other species was described as the new Botryosphaeria anamorph within Lasiodiplodia, namely L. gonubiensis. This species grows endophytically on native S. cordatum in South Africa and is the first species in Lasiodiplodia to be found on native trees in the country. Identification of the new species was based on conidial and cultural morphology and DNA sequence data of the rDNA internal transcribed spacers, ITS1 and ITS2. Identification and description of L. gonubiensis is presented and discussed in Chapter 2. In total nine Botryosphaeria spp. were isolated from native Syzygium cordatum in South Africa. These include B. parva, B. ribis, B. lutea, B. australis, B. rhodina, B. dothidea, Fusicoccum mangiferum, Lasiodiplodia gonubiensis and an unknown Botryosphaeria sp. The isolates related to B. ribis, B. parva and F. mangiferum were the most abundant, while only one isolate represented B. dothidea. Species were identified based on morphological characteristics of their anamorphs combined with ITS rDNA sequence data. Some species, such as B. parva and B. ribis, could not be distinguished based on morphology or ITS rDNA data. A PCR-RFLP fingerprinting technique was, therefore, used to distinguish isolates of these two species. Once again this technique has proven useful and reliable in identification of Botryosphaeria isolates, including cryptic species. However, isolates of closely related B. lutea and B. australis could not be distinguished using this technique. It could be of interest to develop PCR-RFLP identification system that could be used in identification of the latter species. Identification and characterization of Botryosphaeria spp. are presented in Chapter 3. Isolates of all Botryosphaeria spp., obtained from native Syzygium cordatum in this study, caused lesions on the stems of Eucalyptus camaldulensis and S. cordatum in trials conducted under greenhouse conditions. Except for Fusicoccum mangiferum, all the other Botryosphaeria spp. were more pathogenic on Eucalyptus than on S. cordatum. The most pathogenic species on Eucalyptus were B. rhodina, B. ribis and B. lutea, whileF. mangiferum and B. ribis were the most pathogenic on S. cordatum. Botryosphaeria dothidea and L. gonubiensis were the least pathogenic on both hosts. The results obtained from this trial clearly show that Botryosphaeria spp. on S. cordatum pose a potential threat to exotic Eucalyptus plantations. Future study should be conducted under field conditions to evaluate data obtained in greenhouse trials. These results were presented and discussed in Chapter 4. The results presented in this study provide the first detailed information on Botryosphaeria spp. on the native Myrtaceae in South Africa. Most of the species isolated from Syzygium cordatum are not known on Eucalyptus in the country. All of the Botryosphaeria spp. obtained in this study are pathogenic to Eucalyptus, and thus pose a threat to this host. Large number of B. ribis, B. parva and F. mangiferum isolates obtained from the native S. cordatum could imply their origin in this region. Further sampling is needed on myrtaceous trees native to the Southern African region, as well as on Eucalyptus. Population studies on the most abundant and most pathogenic Botryosphaeria spp., should provide more information on the movement and origin of these pathogens. The results from this study also highlights the need for quarantine measures to avoid the introduction of new Botryosphaeria spp. or new strains that can be more pathogenic to either native or cultivated plants. Please cite as follows Pavlic, D 2004, Botryosphaeria species on native South African Syzygium cordatum and their potential threat to Eucalyptus , MSc dissertation, University of Pretoria, Pretoria, viewed yymmdd < http://upetd.up.ac.za/thesis/available/etd-02062006-112938/ > / Dissertation (MSc)--University of Pretoria, 2007. / Microbiology and Plant Pathology / MSc / Unrestricted