Fungos para o controle biológico de Miconia calvescens com especial referência a Coccodiella miconiae

• Ano de defesa: 2008
• Autor(a) principal: Alves, Janaina Lana
• Orientador(a): Barreto, Robert Weingart
• Banca de defesa: Kasuya, Maria Catarina Megumi , Soares, Dartanhã José
• Tipo de documento: Dissertação
• Tipo de acesso: Acesso aberto
• Idioma: por
• Instituição de defesa: Universidade Federal de Viçosa
• Programa de Pós-Graduação: Mestrado em Fitopatologia
• Departamento: Etiologia; Epidemiologia; Controle
• País: BR
• Palavras-chave em Português: Controle biológico; Miconia calvescens; Coccodiella miconiae
• Palavras-chave em Inglês: Biological control; Miconia calvescens; Coccodiella miconiae
• Área do conhecimento CNPq: CNPQ::CIENCIAS AGRARIAS::AGRONOMIA::FITOSSANIDADE::FITOPATOLOGIA
• Link de acesso: http://locus.ufv.br/handle/123456789/4364

This work represents an additional contribuition towards the biological control of Miconia calvescens (Melastomataceae), a shrub or small tree native from the Neotropics (including from Brazil) which became one of the most ecosystem invaders in the Pacific Islands. Two areas were covered in this work: 1) a complementary description of the pathogenic mycobiota associated to M. calvescens, and 2) a complementary investigation on the manipulation of Coccodiela miconiae a fungus recognized as having a great potential for utilization as a classical biocontrol agent to be used agains M. calvescens. Since 1995, a systematic survey of fungal pathogens associated with M. calvescens have been performed in search of potential classical biocontrol agents to be introduced into Hawaii. These surveys covered selected areas in Brazil, Costa Rica and Ecuador. A significant diversity of fungi was found associated with this host besides non-fungal pathogens such as a phytoplasme and two nematodes. In a recent publication the following fungi were described in association with miconia: Coccodiella miconiae, Glomerella cingulata (=Colletotrichum gloeosporioides f. sp. miconiae), Guignardia miconiae, Korunomyces prostratus and Pseudocercospora tamonae. Two of these represented new taxa: G. miconiae and K. prostratus. In the present work the following species are additionally described: Hyalosphaera miconiae, Hyalosphaera sp. nov, Lembosia melastomatum, Microsphaeropsis clidemiae, Microsphaeropsis sp. nov., Myrothecium sp. nov and Phyllachora sp. nov. The sole fungal species that was actually introduced into Hawaii (and later in French Polynesia) was C. gloeosporioides f. sp. miconiae. Although this fungus has successfully established after its introduction, its impact on the plant populations was limited and it is now regarded necessary the introduction of additional biocontrol agents (either pathogens of arthropods) in order to reach an adequate level of control of miconia. Amont the fungi regarded as promising for that purpose is C. miconiae. It causes a severe disease on miconia (yellow pustule disease) in natural conditions despite being often severely challenged by a range of mycoparasites. Unfortunately an earlier work showed that C. miconiae is very difficult to manipulate under controlled conditions making its use in classical biological control difficult. It is a biotrophic parasite that is hard to preserve and inoculate. Repeated attempts to inoculate healthy plants of M. calvescens with spores collected from the fruiting structures of C. miconiae failed to result in infection. A lack of knowledge on the biology of C. miconiae was regarded as the likely cause of such failures and the elucidation of critical aspects of the fungal biology might result in overcoming such difficulties besides allowing for a better understanding about the genus Coccodiella. The study involved a series of tests aimed at determining: 1) the best method for obtaining viable ascospores, including a series of tests aimed at breaking a conjectured spore dormancy; 2) the effect of temperature and light regime on ascospore germination; 3) the viability of ascospores after a series of washing in water, increasing spore dilutions, maintenance in mineral oil, or exposed to increasing concentrations of manitol; 4) the best among a series of methods of preservation of infected leaves e 5) the best method of inoculation of plants. It was concluded that the most effective way of obtaining viable spores was through the suspension of stromata in water under aggitation for 3-4 hours. The inoculum obtained as such was infective when used immediately after release from the stromata. Ascospore germination was favored by incubation at 25 ºC, under a daily 12 hours light regime. This combination of results clearly demonstrated that an initial conjecture that exposition of ascospores to water might damage them was false. Subjecting infected miconia leaves to drying in a plant press for two days was the best method for inoculum preservation among these that were tested. These results are critical for the establishment of a protocol that will finally allow the manipulation and eventually the introduction of C. miconiae as a classical biocontrol agent in the Pacific.