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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
81

Evaluation of a plant-herbivore system in determining potential efficacy of a candidate biological control agent, cornops aquaticum for water hyacinth, eichhornia crassipes

Bownes, Angela January 2009 (has links)
Water hyacinth, Eichhornia crassipes Mart. Solms-Laubach (Pontederiaceae), a freefloating aquatic macrophyte of Neotropical origin, was introduced into South Africa as an ornamental aquarium plant in the early 1900’s. By the 1970’s it had reached pest proportions in dams and rivers around the country. Due to the sustainability, cost efficiency and low environmental risk associated with biological control, this has been a widely used method in an attempt to reduce infestations to below the threshold where they cause economic and ecological damage. To date, five arthropod and one pathogen biocontrol agents have been introduced for the control of water hyacinth but their impact has been variable. It is believed that their efficacy is hampered by the presence of highly eutrophic systems in South Africa in which plant growth is prolific and the negative effects of herbivory are therefore mitigated. It is for these reasons that new, potentially more damaging biocontrol agents are being considered for release. The water hyacinth grasshopper, Cornops aquaticum Brüner (Orthoptera: Acrididae), which is native to South America and Mexico, was brought into quarantine in Pretoria, South Africa in 1995. Although the grasshopper was identified as one of the most damaging insects associated with water hyacinth in its native range, it has not been considered as a biocontrol agent for water hyacinth anywhere else in the world. After extensive host-range testing which revealed it to be safe for release, a release permit for this candidate agent was issued in 2007. However, host specificity testing is no longer considered to be the only important component of pre-release screening of candidate biocontrol agents. Investigating biological and ecological aspects of the plant-herbivore system that will assist in determination of potential establishment, efficacy and the ability to build up good populations in the recipient environment are some of the important factors. This thesis is a pre-release evaluation of C. aquaticum to determine whether it is sufficiently damaging to water hyacinth to warrant its release. It investigated interactions between the grasshopper and water hyacinth under a range of nutrient conditions found in South African water bodies as well as the impact of the grasshopper on the competitive performance of water hyacinth. Both plant growth rates and the response of water hyacinth to herbivory by the grasshopper were influenced by nutrient availability to the plants. The ability of water hyacinth to compensate for loss of tissue through herbivory was greater under eutrophic nutrient conditions. However, a negative linear relationship was found between grasshopper biomass and water hyacinth performance parameters such as biomass accumulation and leaf production, even under eutrophic conditions. Water hyacinth’s compensatory ability in terms of its potential to mitigate to detrimental effects of insect feeding was dependent on the amount of damage caused by herbivory by the grasshopper. Plant biomass and the competitive ability of water hyacinth in relation to another freefloating aquatic weed species were reduced by C. aquaticum under eutrophic nutrient conditions, in a short space of time. It was also found that grasshopper feeding and characteristics related to their population dynamics such as fecundity and survival were significantly influenced by water nutrient availability and that environmental nutrient availability will influence the control potential of this species should it be released in South Africa. Cornops aquaticum shows promise as a biocontrol agent for water hyacinth but additional factors that were not investigated in this study such as compatibility with the South African climate and the current water hyacinth biocontrol agents need to be combined with these data to make a decision on its release. Possible management options for this species if it is to be introduced into South Africa are discussed.
82

Establishment and impact of the sap-sucking mirid, Falconia intermedia (Distant) (Hemiptera: Miridae) on Lantana camara (Verbenaceae) varieties in the Eastern Cape Province, South Africa

Heshula, Unathi-Nkosi Lelethu Peter January 2005 (has links)
The biological control of the weedy complex Lantana camara (L.) (Verbenaceae) has been ongoing in South Africa for over 40 years. Despite this, the weed is still not under sufficient control and continues to invade new territories in the country. The biological control programme needs to be bolstered with releases of new and potentially damaging biological control agents. A promising biological control agent endemic to Central America, Falconia intermedia (Distant) (Hemiptera: Miridae), was imported into quarantine from Jamaica in 1994. This agent was released on sites in KwaZulu-Natal and Limpopo provinces of South Africa in 1999. Even though it initially established and damaged L. camara, populations died out at most of the release sites. As varietal difference and adverse climate have been cited as the reason for non-establishment and ineffective control in L. camara biocontrol programmes worldwide, this study attempts to investigate the role that these two factors play in this weed herbivore relationship. Laboratory no-choice trials were conducted to determine the varietal performance of F intermedia, among five Eastern Cape varieties of the weed from East London, Whitney Farm, Heather Glen Farm, Port Alfred and Lyndhurst Farm, and a variety from the Plant Protection Research Institute (PPRI), Pretoria. However, there were differences in performance as the adult mirids performed better on white-pink varieties from Whitney Farm and Heather Glen Farm. To test varietal preference in field conditions, field releases of F intermedia were also made at East London, Whitney Farm, Heather Glen Farm, Port Alfred and Lyndhurst Farm. Post release evaluations were conducted monthly for two years (2002 and 2003). The insect established at East London and Whitney Farm, both of which have white-pink varieties. Insect populations quickly died out at the Lyndhurst Farm and Port Alfred sites, which have dark pink varieties. It is suggested that field conditions may have resulted in poor plant quality and led indirectly to varietal preference, and to non-establishment at these two sites. With the onset of cooler weather, populations disappeared at Heather Glen Farm. This suggested that F. intermedia was suitable for release in more subtropical areas within South Africa where climatic conditions would be suitable throughout the year. The mirid performed well at Whitney Farm, resulting in significant reduction in plant growth parameters such as height and percentage cover, and increasing the cover of other flora growing beneath L. camara plants. Finally, ways to improve the efficacy of this agent are considered in an effort towards better control of L. camara in South Africa.
83

The biology, behaviour and survival of pupating false codling moth, Thaumatotibia leucotreta (Meyrick) (Lepidoptera: Tortricidae), a citrus pest in South Africa

Love, Claire Natalie January 2015 (has links)
Control of the citrus pest, false codling moth (FCM), Thaumatotibia leucotreta Meyrick (Lepidoptera: Tortricidae) is crucial for the South African citrus industry. The economic losses and phytosanitary status of this pest, coupled with increased consumer awareness and demands, has created a need for effective, IPM-compatible control measures for use against the soil-dwelling life stages of FCM. Promising developments in the field of microbial control through the use of entomopathogenic fungi (EPF) and entomopathogenic nematodes (EPNs) have highlighted the need for research regarding pupation biology, behaviour and survival of FCM, as a good understanding of biology of the target organism is an important component of any biological control programme. The aim of this study was to improve the current understanding of FCM pupation habits through the manipulation of soil texture class, ground cover, shading, soil compaction, air temperature, and soil moisture in the laboratory. These findings would then be used to aid the biological control programmes using EPF and EPNs against FCM in the soil. Three soil texture classes (sandy loam, silt loam and silty clay loam) were obtained from orchards for use in the study. FCM larvae were allowed to drop into the soil of their own accord and the pupation behaviour that followed was then captured on film with pupae formed in the soil being kept in order to measure adult eclosion. In general, very few abiotic factors had a clear influence on FCM pupation. Larval wandering time and distance was short, but also variable between individuals. Distance did increase when soils were moist. Pupation depth was shallow, with pupal cocoons generally being formed on the soil surface. Depth of pupation was less than one centimetre for all abiotic conditions, with little burrowing into soil. Eclosion success was higher for sandier soils when these were dry and uncompacted, but the addition of both moisture and soil compaction increased FCM eclosion success. FCM was sensitive to desiccation when the soils were dry and temperature limits of 15 °C and 32 °C had a strongly negative impact on eclosion success. Preferences for particular abiotic conditions were limited to only certain moisture conditions when interacting with soil texture class and a preference for pupating in soil when it is available. Limited preference was found for particular soil textures despite this having a strong influence on eclosion success, but individuals did appear to pupate in close proximity to one another. Viable direct habitat manipulation for FCM control could not be identified. These results and all of the abiotic variables measured have important implications for EPF and EPN application, survival and persistence in the soil in order to improve the ability of these biological control agents to control FCM. These are discussed in each chapter.
84

Influência da sinigrina no comportamento de busca e seleção de presas pelo predador Orius insidiosus (Say, 1832) (Hemiptera: Anthocoridae)

Maeda, Jaqueline Midori [UNESP] 18 December 2012 (has links) (PDF)
Made available in DSpace on 2014-06-11T19:25:17Z (GMT). No. of bitstreams: 0 Previous issue date: 2012-12-18Bitstream added on 2014-06-13T19:32:16Z : No. of bitstreams: 1 maeda_jm_me_jabo.pdf: 465784 bytes, checksum: 874c1d11209485811452057c1724aded (MD5) / Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / O objetivo foi investigar a influência da sinigrina no comportamento de busca e seleção do predador Orius insidiosus (Say, 1832) (Hemiptera: Anthocoridae) pela presa Plutella xylostella (L., 1758) (Lepidoptera: Plutellidae). Foi avaliado o desenvolvimento, reprodução e preferência de O. insidiosus predando lagartas de P. xylostella alimentadas com sinigrina. Foi possível observar que os predadores que consumiram lagartas alimentadas com folhas de couve pulverizadas com sinigrina na concentração de 1,6 mg/mL apresentaram período ninfal mais curto, menor consumo de presas e também menor viabilidade ninfal. Os predadores adultos consumiram maior número de presas que ingeriram sinigrina e a exposição à substância proporcionou maior fertilidade de ovos. Quando os predadores entraram em contato com a sinigrina por meio da superfície pulverizada, a substância estimulou o consumo na fase ninfal, não apresentando influência negativa em outros aspectos biológicos da fase adulta. No segundo ínstar e na fase adulta, os predadores preferiram presa que ingeriram sinigrina; no terceiro e no quarto ínstar ocorreu preferência por lagartas que não ingeriram a substância e no quinto não ocorreu preferência. A seleção pelos predadores que tiveram experiência prévia com presas que ingeriram singrina, em geral, não foi influenciada pela substância. Em casa telada, a longevidade dos adultos e o consumo de presas foram menores quando os predadores foram alimentados com lagartas criadas com folhas pulverizadas com sinigrina. Com base nestes resultados é possível concluir que a sinigrina tem influência sob a preferência e o consumo de presas pelo predador em laboratório, no entanto, em casa telada, a sinigrina tem efeitos não favoráveis ao predador O. inisidiosus / The aim was to investigate the influence of sinigrin in search behavior and prey selection of predator Orius insidiosus (Say, 1832) (Hemiptera: Anthocoridae) by Plutella xylostella (L., 1758) (Lepidoptera: Plutellidae). We evaluated the development, reproduction and preference of O. insidiosus preying P. xylostella caterpillars fed on kale leaves treated with sinigrin. It was observed that the predators that consumed caterpillars fed on kale leaves sprayed with sinigrin at concentration of 1.6 mg / mL, showed nymphal period shorter, smaller prey consumption and also lower nymphal survival. When the predators contacted the sinigrin throught the sprayed surface, it was stimulated the consumption of prey to the nymphal stage, moreover, showed no negative influence on the biological aspects of adults. In the second larvae instar and adult, predators preferred prey fed on leaves treated with sinigrin, on the third and fourth instar occurred preference by larvae that not ingesting the substance and fifth instar there was no preference. Predators that had previous experience with prey fed on kale leaves treated with sinigrin, in general, were not affected in the process of selection prey. Under greenhouse conditions, the longevity of adults and prey consumption were lower when predators were fed caterpillars reared on leaves sprayed with sinigrin. Based on these results we conclude that the sinigrin has influence on the preference and prey consumption by the predator in the laboratory. However, under greenhouse conditions sinigrin has not unfavorable effects to the predator O. insidiosus
85

Secretômica de Trichoderma atroviride e Trichoderma harzianum frente a Guignardia e citricarpa, agente etiológico da Pinta Preta dos Citros

Lima, Fernanda Blauth de 15 April 2016 (has links)
Os agentes de controle biológico têm recebido grande reconhecimento, e o seu uso tem contribuído como um complemento ou substituição de agroquímicos. No entanto, existem poucos estudos sobre o controle biológico da Pinta Preta dos Citros, causada pelo fungo Guignardia citricarpa, o que impede o seu mercado in natura, além de prejudicar a sua exportação pelo uso intensivo de insumos químicos para controlar este patógeno. Os fungos do gênero Trichoderma são agentes de controle utilizados em todo o mundo contra vários fitopatógenos relevantes. Este estudo visou identificar proteínas extracelulares secretadas por T. atroviride T17 e por T.harzianum T1A, eficazes para o controle de G. citricarpa. Por eletroforese bidimensional (2D) foram obtidos perfis de proteínas secretadas por Trichoderma em meio de glicose (controle) e em meio suplementado com micélio desativado de G. citricarpa. As proteínas foram identificadas por LC-MS/MS mostrando que ambas as espécies secretam proteínas diferentes. Foram identificadas 68 proteínas das 178 diferencialmente expressas por T. harzianum, sendo a maioria relacionada aos mecanismos de biocontrole, mesmo no meio controle. Foi verificado que em contato com o patógeno a expressão de proteínas relacionadas com o metabolismo primário diminui. Por outro lado, Trichoderma atroviride mostrou uma maior expressão de proteínas relacionadas com biocontrole na presença de micélio do patógeno. Nesta espécie identificamos 59 proteínas de 116 diferencialmente expressas, principalmente proteínas relacionadas com a degradação da parede celular: α- manosidase, quitinase, mutanase, glicosidase, endoquitinase e, algumas famílias de glicoside hidrolases. Os resultados indicam que estas espécies apresentam um elevado potencial como agentes de controle de G. citricarpa. Os resultados são pioneiros em detalhar a interação de Trichoderrma com G. citricarpa, por meio da análise do secretoma. / Submitted by Ana Guimarães Pereira (agpereir@ucs.br) on 2016-05-11T14:24:21Z No. of bitstreams: 1 Tese Fernanda Blauth de Lima.pdf: 5347447 bytes, checksum: 314027a9e2af4a7cf6e30be761df9f99 (MD5) / Made available in DSpace on 2016-05-11T14:24:21Z (GMT). No. of bitstreams: 1 Tese Fernanda Blauth de Lima.pdf: 5347447 bytes, checksum: 314027a9e2af4a7cf6e30be761df9f99 (MD5) Previous issue date: 2016-05-11 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior, CAPES. / Biological control agents (BCA) have received great recognition, and their use has contributed as a complement or replacement of agrochemicals. However, there are few studies on the biological control of Black spot of citrus, caused by the fungus Guignardia citricarpa, which prevents the market in natura, besides damaging their export by the intensive use of chemical inputs to control this pathogen. Trichoderma fungi are the most applied worldwide BCA against various relevant plant pathogens. The purpose of this study was to identify extracellular proteins secreted by T. atroviride T17 and of T. harzianum T1A, which are effective for the control of G. citricarpa. Bidimensional electrophoresis (2D) allowed obtaining the secreted protein profiles of Trichoderma grown in glucose medium (control) and in medium containing inactivated mycelium of G. citricicarpa. From the 178 differentially expressed proteins by T. harzianum, 68 were identified, most of them related to biocontrol mechanisms, even in the control medium. In the presence of the pathogen, the expression of proteins related to the metabolism decreases. On the other hand, Trichoderma atroviride showed higher expression of proteins related to biocontrol pathogen when grown in the presence of pathogen mycelium, when compared to the control medium. From the 116 differentially expressed proteins, 59 were identified, mainly proteins related to fungi cell wall degradation such as α-mannosidase, chitinase, mutanase, glycosidase, endochitinase and, some families of glycoside hydrolases. The results indicate that these species have a high potential as biocontrol agents of G. citricicarpa. These results are pioneers in to detail the Trichoderrma interaction with G. citricicarpa through the secretome analysis.
86

The development of a putative microbial product for use in crop production

Gumede, Halalisani January 2008 (has links)
The challenges faced by the agricultural sector especially around improving production yields using environmentally friendly solutions have received market attention. Biological intervention can range from application of biological products to enhance the nutritional value of crops or to control plant pathogens. Biostart, a biological product that demonstrated growth enhancement when applied in lettuce crops is currently in the market. The product is comprised of a consortium of bacterial isolates (Bacillus licheniformis, Brevibacillus laterosporus and Bacillus laterosporus) but the contribution of the individual isolates to growth enhancement had not been elucidated. Green house experiments on lettuce seedlings with individual and mixed treatments were commissioned to determine such contribution. There was either no or marginal growth enhancement observed in the experiments. The results showed that the product was effective as a consortium and not as individual isolates. Further isolation and screening for potential Bacilli with antifungal properties was undertaken. An isolate identified as Bacillus subtilis that demonstrated inhibition against a wide spectrum of fungi, and especially the phytopathogenic Verticillium dahliae and Fusarium oxysporum, was successfully identified. The isolate was cryo-preserved and cultivated to significant levels at bench scale. A characterized comparison of different putative products with known systematic fungicide showed potential application even of heat treated products. The product showed control V. dahliae when tested in green houses with potatoes and tomatoes as test crops. This isolate has been targeted for further development as a biological control product.
87

Metodologia de criação, aspectos biológicos e custo de produção de Xylocoris afer predando ovos de Corcyra cephalonica e Plutella xylostella /

Vieira, Natalia Fernanda. January 2016 (has links)
Orientador: Sergio Antonio De Bortoli / Banca: Roberto Marchi Goulart / Banca: Raphael de Campos Castilho / Resumo: O objetivo desta pesquisa foi adequar uma metodologia de criação para o predador Xylocoris afer e avaliar, bem como aspectos biológicos e o custo de produção predando ovos de Corcyra cephalonica ou Plutella xylostella. Visando otimizar e adequar uma metodologia para multiplicação de X. afer em condições de laboratório, foi estabelecida uma colônia do predador utilizando como referência, a metodologia de criação de outra espécie de Anthocoridae, Orius insidiosus. Porém, nos recipientes de criação onde os insetos foram criados, não foram utilizadas inflorescências de picão preto (Bidens pilosa), comumente empregada como substrato de oviposição, mas pequenos rolos de algodão, eliminando a dependência de um substrato vegetal. O experimento visando obter informações sobre os aspectos biológicos de X. afer, foi conduzido inicialmente com ninfas de 12-24h de idade, uma por placa, num total de 60 ninfas (60 repetições). Em cada placa foram colocados, diariamente, ovos de P. xylostella ou ovos de C. cephalonica e um chumaço de algodão umedecido com água destilada. As avaliações foram realizadas a cada 24 horas. Os adultos foram separados por sexo, acasalados e mantidos também em placas de Petri para a verificação das características reprodutivas e longevidade. Foram avaliados os seguintes parâmetros: duração, viabilidade e consumo dos estádios ninfais e da fase ninfal; consumo e longevidade de machos e fêmeas; ovos por fêmea e fertilidade dos ovos. Os dados biológicos também foram uti... (Resumo completo, clicar acesso eletrônico abaixo) / Mestre
88

Influência da sinigrina no comportamento de busca e seleção de presas pelo predador Orius insidiosus (Say, 1832) (Hemiptera: Anthocoridae) /

Maeda, Jaqueline Midori. January 2012 (has links)
Orientador: Sérgio Antônio De Bortoli / Banca: Odair Aparecido Fernandes / Banca: Laila Herta Mihsfeldt / Resumo: O objetivo foi investigar a influência da sinigrina no comportamento de busca e seleção do predador Orius insidiosus (Say, 1832) (Hemiptera: Anthocoridae) pela presa Plutella xylostella (L., 1758) (Lepidoptera: Plutellidae). Foi avaliado o desenvolvimento, reprodução e preferência de O. insidiosus predando lagartas de P. xylostella alimentadas com sinigrina. Foi possível observar que os predadores que consumiram lagartas alimentadas com folhas de couve pulverizadas com sinigrina na concentração de 1,6 mg/mL apresentaram período ninfal mais curto, menor consumo de presas e também menor viabilidade ninfal. Os predadores adultos consumiram maior número de presas que ingeriram sinigrina e a exposição à substância proporcionou maior fertilidade de ovos. Quando os predadores entraram em contato com a sinigrina por meio da superfície pulverizada, a substância estimulou o consumo na fase ninfal, não apresentando influência negativa em outros aspectos biológicos da fase adulta. No segundo ínstar e na fase adulta, os predadores preferiram presa que ingeriram sinigrina; no terceiro e no quarto ínstar ocorreu preferência por lagartas que não ingeriram a substância e no quinto não ocorreu preferência. A seleção pelos predadores que tiveram experiência prévia com presas que ingeriram singrina, em geral, não foi influenciada pela substância. Em casa telada, a longevidade dos adultos e o consumo de presas foram menores quando os predadores foram alimentados com lagartas criadas com folhas pulverizadas com sinigrina. Com base nestes resultados é possível concluir que a sinigrina tem influência sob a preferência e o consumo de presas pelo predador em laboratório, no entanto, em casa telada, a sinigrina tem efeitos não favoráveis ao predador O. inisidiosus / Abstract: The aim was to investigate the influence of sinigrin in search behavior and prey selection of predator Orius insidiosus (Say, 1832) (Hemiptera: Anthocoridae) by Plutella xylostella (L., 1758) (Lepidoptera: Plutellidae). We evaluated the development, reproduction and preference of O. insidiosus preying P. xylostella caterpillars fed on kale leaves treated with sinigrin. It was observed that the predators that consumed caterpillars fed on kale leaves sprayed with sinigrin at concentration of 1.6 mg / mL, showed nymphal period shorter, smaller prey consumption and also lower nymphal survival. When the predators contacted the sinigrin throught the sprayed surface, it was stimulated the consumption of prey to the nymphal stage, moreover, showed no negative influence on the biological aspects of adults. In the second larvae instar and adult, predators preferred prey fed on leaves treated with sinigrin, on the third and fourth instar occurred preference by larvae that not ingesting the substance and fifth instar there was no preference. Predators that had previous experience with prey fed on kale leaves treated with sinigrin, in general, were not affected in the process of selection prey. Under greenhouse conditions, the longevity of adults and prey consumption were lower when predators were fed caterpillars reared on leaves sprayed with sinigrin. Based on these results we conclude that the sinigrin has influence on the preference and prey consumption by the predator in the laboratory. However, under greenhouse conditions sinigrin has not unfavorable effects to the predator O. insidiosus / Mestre
89

Secretômica de Trichoderma atroviride e Trichoderma harzianum frente a Guignardia e citricarpa, agente etiológico da Pinta Preta dos Citros

Lima, Fernanda Blauth de 15 April 2016 (has links)
Os agentes de controle biológico têm recebido grande reconhecimento, e o seu uso tem contribuído como um complemento ou substituição de agroquímicos. No entanto, existem poucos estudos sobre o controle biológico da Pinta Preta dos Citros, causada pelo fungo Guignardia citricarpa, o que impede o seu mercado in natura, além de prejudicar a sua exportação pelo uso intensivo de insumos químicos para controlar este patógeno. Os fungos do gênero Trichoderma são agentes de controle utilizados em todo o mundo contra vários fitopatógenos relevantes. Este estudo visou identificar proteínas extracelulares secretadas por T. atroviride T17 e por T.harzianum T1A, eficazes para o controle de G. citricarpa. Por eletroforese bidimensional (2D) foram obtidos perfis de proteínas secretadas por Trichoderma em meio de glicose (controle) e em meio suplementado com micélio desativado de G. citricarpa. As proteínas foram identificadas por LC-MS/MS mostrando que ambas as espécies secretam proteínas diferentes. Foram identificadas 68 proteínas das 178 diferencialmente expressas por T. harzianum, sendo a maioria relacionada aos mecanismos de biocontrole, mesmo no meio controle. Foi verificado que em contato com o patógeno a expressão de proteínas relacionadas com o metabolismo primário diminui. Por outro lado, Trichoderma atroviride mostrou uma maior expressão de proteínas relacionadas com biocontrole na presença de micélio do patógeno. Nesta espécie identificamos 59 proteínas de 116 diferencialmente expressas, principalmente proteínas relacionadas com a degradação da parede celular: α- manosidase, quitinase, mutanase, glicosidase, endoquitinase e, algumas famílias de glicoside hidrolases. Os resultados indicam que estas espécies apresentam um elevado potencial como agentes de controle de G. citricarpa. Os resultados são pioneiros em detalhar a interação de Trichoderrma com G. citricarpa, por meio da análise do secretoma. / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior, CAPES. / Biological control agents (BCA) have received great recognition, and their use has contributed as a complement or replacement of agrochemicals. However, there are few studies on the biological control of Black spot of citrus, caused by the fungus Guignardia citricarpa, which prevents the market in natura, besides damaging their export by the intensive use of chemical inputs to control this pathogen. Trichoderma fungi are the most applied worldwide BCA against various relevant plant pathogens. The purpose of this study was to identify extracellular proteins secreted by T. atroviride T17 and of T. harzianum T1A, which are effective for the control of G. citricarpa. Bidimensional electrophoresis (2D) allowed obtaining the secreted protein profiles of Trichoderma grown in glucose medium (control) and in medium containing inactivated mycelium of G. citricicarpa. From the 178 differentially expressed proteins by T. harzianum, 68 were identified, most of them related to biocontrol mechanisms, even in the control medium. In the presence of the pathogen, the expression of proteins related to the metabolism decreases. On the other hand, Trichoderma atroviride showed higher expression of proteins related to biocontrol pathogen when grown in the presence of pathogen mycelium, when compared to the control medium. From the 116 differentially expressed proteins, 59 were identified, mainly proteins related to fungi cell wall degradation such as α-mannosidase, chitinase, mutanase, glycosidase, endochitinase and, some families of glycoside hydrolases. The results indicate that these species have a high potential as biocontrol agents of G. citricicarpa. These results are pioneers in to detail the Trichoderrma interaction with G. citricicarpa through the secretome analysis.
90

The isolation, genetic characterisation and biological activity of a South African Phthorimaea operculella granulovirus (PhopGV-SA) for the control of the Potato Tuber Moth, Phthorimaea operculella (Zeller)

Jukes, Michael David January 2015 (has links)
The potato tuber moth, Phthorimaea operculella (Zeller), is a major pest of potato crops worldwide causing significant damage to both field and stored tubers. The current control method in South Africa involves chemical insecticides, however, there is growing concern on the health and environmental risks of their use. The development of novel biopesticide based control methods may offer a potential solution for the future of insecticides. In this study a baculovirus was successfully isolated from a laboratory population of P. operculella. Transmission electron micrographs revealed granulovirus-like particles. DNA was extracted from recovered occlusion bodies and used for the PCR amplification of the lef-8, lef-9, granulin and egt genes. Sequence data was obtained and submitted to BLAST identifying the virus as a South African isolate of Phthorimaea operculella granulovirus (PhopGV-SA). Phylogenetic analysis of the lef-8, lef-9 and granulin amino acid sequences grouped the South African isolate with PhopGV-1346. Comparison of egt sequence data identified PhopGV-SA as a type II egt gene. A phylogenetic analysis of egt amino acid sequences grouped all type II genes, including PhopGV-SA, into a separate clade from types I, III, IV and V. These findings suggest that type II may represent the prototype structure for this gene with the evolution of types I, III and IV a result of large internal deletion events and subsequent divergence. PhopGV-SA was also shown to be genetically more similar to South American isolates (i.e. PhopGV-CHI or PhopGV-INDO) than it is to other African isolates, suggesting that the South African isolate originated from South America. Restriction endonuclease profiles of PhopGV-SA were similar to those of PhopGV-1346 and PhopGV-JLZ9f for the enzymes BamHI, HindIII, NruI and NdeI. A preliminary full genome sequence for PhopGV-SA was determined and compared to PhopGV-136 with some gene variation observed (i.e. odv-e66 and vp91/p95). The biological activity of PhopGV-SA against P. operculella neonate larvae was evaluated with an estimated LC₅₀ of 1.87×10⁸ OBs.ml⁻¹ being determined. This study therefore reports the characterisation of a novel South African PhopGV isolate which could potentially be developed into a biopesticide for the control of P. operculella.

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